Image coding device and image coding method coding a VOP rate flag

TECHNICAL FIELD

The present invention relates to an image coding device and an image coding method which perform image processing.

BACKGROUND ART

Conventionally, it is always necessary at the decoding side that the analysis of VOP header information be preceded by analyses of a VOP start code, a modulo time base and a VOP time increment which are contained in each VOP header, because no distinction can be made between VOP not to be analyzed (information to be decimated in the case of a low speed shot of an image signal) and VOP to be analyzed (information not to be decimated in the case of a low speed shot of an image signal); hence, there is a problem that the processing involved is cumbersome and low in accuracy.

For decoding and synthesizing encoded signals respectively corresponding to a subject, a background, a log and similar objects which form a pictorial image, it is necessary that each object be added with a synthesizing timing signal (information representing absolute time) necessary for decoding and synthesizing the object. Without the information indicative of absolute time, an image decoding device cannot synthesize the object, and hence it is incapable of image reconstruction. In short, in the case of generating one pictorial image from a plurality of objects including those having no information representative of absolute time, it is impossible with the prior art to combine objects having the required information with those having no such information.

Moreover, the bit length of the modulo time base increases until the next GOV header is multiplexed-this raises a problem that the bit length of the modulo time base keeps on increasing when the GOV header, which is an option, is not multiplexed.

With a view to solving such problems as referred to above, the present invention is to provide an image coding device and an image coding method whose processing accuracies improve through simple processing.

Another object of the present invention is to provide an image coding device and an image coding method which permit the generation of a pictorial image composed of a plurality of objects based on a time code.

Still another object of the present invention is to prevent the generation of an unnecessary amount of information.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, an image coding device that encodes a sequence of moving images and generates an encoded bit stream comprises multiplexing means configured to multiplex a header information of the moving image sequence, wherein said multiplexing means is configured to multiplex display time multiplex identification information indicating whether frame rate information that uniquely identifies display time of each image contained in a moving image sequence, and to multiplex said display time information according to the value of said display time multiplex identification information, wherein said display time information is represented as direct predetermined frame rate value or as parameter value to be used to derive frame rate value.

According to a further aspect of the present invention an image coding method for encoding a sequence of moving images and generating an encoded bit stream comprises multiplexing a header information of the moving image sequence, multiplexing display time multiplex identification information indicating whether frame rate information that uniquely identifies display time of each image contained in a moving image sequence is multiplexed into the header information of the moving image sequence; and multiplexing said display time information according to the value of said display time multiplex identification information, wherein said display time information is represented as direct predetermined frame rate value or as parameter value to be used to derive frame rate value.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="f0001">Fig. 1</figref> is a diagram depicting the video data structure in MPEG-4; <figref idref="f0002">Fig. 2</figref> is a diagram showing a concrete example of VOP; <figref idref="f0003">Fig. 3</figref> is a block diagram illustrating a VOP encoder part according to Embodiment 1 of the present invention; <figref idref="f0004">Fig. 4</figref> is a block diagram illustrating an example of the configuration of a header multiplexing part of the VOP encoder part according to Embodiment 1 of the present invention; <figref idref="f0001">Fig. 5</figref> is a diagram for explaining a modulo time base and a VOP time increment; <figref idref="f0005">Fig. 6</figref> is a block diagram illustrating an example of the configuration of the header multiplexing part of the VOP encoder part according to Embodiment 1 of the present invention; <figref idref="f0006">Fig. 7</figref> is a block diagram depicting a VOP encoder part according to Embodiment 2 of the present invention; <figref idref="f0007">Fig. 8</figref> is a block diagram depicting an example of the configuration of the header multiplexing part of the VOP encoder part according to Embodiment 2 of the present invention; <figref idref="f0008">Fig. 9</figref> is a diagram showing an example of a bit stream; <figref idref="f0008">Fig. 10</figref> is block diagram showing an example of the configuration of a VOP header multiplexing part of a header multiplexing part according to Embodiment 2 of the present invention; <figref idref="f0009">Fig. 11</figref> is a block diagram depicting the internal configuration of a VOP decoder part according to Embodiment 3 of the present invention; <figref idref="f0010">Fig. 12</figref> is a block diagram depicting an example of the configuration of a header analysis part of the VOP decoder part according to Embodiment 3 of the present invention; <figref idref="f0011">Fig. 13</figref> is a block diagram depicting a system for synthesizing a plurality of objects according to Embodiment 3 of the present invention; <figref idref="f0012">Fig. 14</figref> is a block diagram illustrating an example of the configuration of a header analysis part of a VOP decoder part according to Embodiment 4 of the present invention; <figref idref="f0013">Fig. 15</figref> is a block diagram illustrating an example of the configuration of the header analysis part of the VOP decoder part according to Embodiment 4 of the present invention; <figref idref="f0014">Fig. 16</figref> is a block diagram showing the internal configuration of a VOP decoder part according to Embodiment 5 of the present invention; <figref idref="f0015">Fig. 17</figref> is a block diagram illustrating an example of the configuration of a header analysis part of the VOP decoder part according to Embodiment 5 of the present invention; <figref idref="f0016">Fig. 18</figref> is a block diagram illustrating an example of the configuration of a VOP header analysis part of the VOP decoder part according to Embodiment 5 of the present invention; <figref idref="f0017">Fig. 19</figref> is a block diagram showing an example of the configuration of a header analysis part of a VOP decoder part according to Embodiment 6 of the present invention; <figref idref="f0018">Fig. 20</figref> is a block diagram showing an example of the configuration of a VOP header analysis part of the VOP decoder part according to Embodiment 6 of the present invention; <figref idref="f0019">Fig. 21</figref> is a block diagram illustrating an example of the configuration of a header multiplexing part of a VOP encoder part according to Embodiment 7 of the present invention; <figref idref="f0020">Fig. 22</figref> is a block diagram illustrating an example of the configuration of a header multiplexing part of a VOP encoder part according to Embodiment 7 of the present invention; <figref idref="f0021">Fig. 23</figref> is a block diagram depicting an example of the internal configuration of a VOP decoder part according to Embodiment 8 of the present invention; <figref idref="f0022">Fig. 24</figref> is a block diagram depicting an example of the configuration of a header analysis part of the VOP decoder part according to Embodiment 8 of the present invention; <figref idref="f0023">Fig. 25</figref> is a block diagram illustrating a system for synthesizing a plurality of objects according to Embodiment 8 of the present invention; <figref idref="f0024">Fig. 26</figref> is a block diagram depicting an example of the configuration of the header analysis part of the VOP decoder part according to Embodiment 8 of the present invention; <figref idref="f0025">Fig. 27</figref> is a block diagram depicting an example of the internal configuration of the VOP decoder part according to Embodiment 8 of the present invention; <figref idref="f0026">Fig. 28</figref> is block diagram showing an example of the configuration of a header multiplexing part of a VOP encoder part according to Embodiment 9 of the present invention; <figref idref="f0027">Fig. 29</figref> is a block diagram illustrating an example of the configuration of a header analysis part of a VOP decoder part according to Embodiment 10 of the present invention; <figref idref="f0028">Fig. 30</figref> is a block diagram illustrating an example of the configuration of a header multiplexing part of a VOP encoder part according to Embodiment 11 of the present invention; and <figref idref="f0029">Fig. 31</figref> is a block diagram illustrating an example of a header analysis part of a VOP decoder part according to Embodiment 12 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

To facilitate a better understanding of the present invention, a description will be given, with reference to the accompanying drawings, of the best mode for carrying out the invention.

EMBODIMENT 1

In Embodiment 1 a VOP encoder for the MPEG-4 video encoding system disclosed in ISO/IEC JTC11 SC29/WG11/N1796 will be described which is provided with constituents of this embodiment, i.e. means for encoding an image on the basis of object display speed information and means for multiplexing the display speed information onto an encoded bit stream by adding the information for each object.

The MPEG-4 system is a system that regards a moving picture sequence as a set of moving picture objects taking arbitrary forms temporally and spatially and performs encoding and decoding for each moving picture object. In <figref idref="f0001">Fig. 1</figref> there is depicted the video data structure in MPEG-4. In MPEG-4 the moving picture object containing the time axis is referred to as a video object [Video Object (VO)], a component of the VO as a video object layer {Video Object Layer (VOL)], a component of the VOL as a group of video object plane (Group of Video Object Plane (GOP)], and image data which represents the state of the GOP at each time and forms the basic unit of encoding as a video object plane [Video Object Plane (VOP)]. The VO corresponds, for example, to each speaker or his background in a video conference scene; the VOL forms the basic unit having inherent temporal and spatial resolutions of the speaker or background; and the VOP is image data of such a VOL at each time (corresponding to a frame). The GOP is a data structure that forms the basic unit for editing a plurality of VOLs or random access thereto; this data structure need not always be used for encoding.

A concrete example of VOP is shown in <figref idref="f0002">Fig. 2</figref>. In <figref idref="f0002">Fig. 2</figref> there are depicted two VOPs (VOP1 indicating a man and VOP2 a picture on the wall). Each VOP is composed of texture data representing the color gradation level and shape data representing the shape of the VOP. The texture data is composed of a luminance signal of 8 bits per pixel and a color difference signal (of a size subsampled to 1/2 that of the luminance signal in the horizontal and vertical directions), and the shape data is the same binary matrix data as the image size of the luminance signal which sets the inside and outside of the VOP at 0 and 1, respectively.

In the VOP-based moving picture representation a conventional frame image is obtained by arranging a plurality of VOPs in the frame. When the moving picture sequence contains only one VO, each VOP is synonymous with the frame.

In this instance, no shape data exists and only the texture data is encoded.

A description will be given below of an image encoding device of Embodiment 1. This is based on an MPEG-4 video encoder; the MPEG-4 video encoder will hereinafter be referred to as a VOP encoder since it performs encoding for each VOP. Since the operation of the existing VOP encoder is disclosed, for example, in ISO/IEC JTC1/SC29/WG11/N1796, no description will be given of the existing VOP encoder itself, but a description will be given of a VOP encoder that contains constituents of Embodiment 1. <figref idref="f0003">Fig. 3</figref> depicts an example of he configuration of the VOP encoder in Embodiment 1; reference numeral 110 denotes a VOP-to-be-encoded determination part, 111 a shape encoding part, 113 a motion estimation part, 115 a motion compensation part, 118 a texture encoding part, 122 a memory, 124 a header multiplexing part, 126 a video signal multiplexing part, 128 a subtractor, and 129 an adder.

Next, the operation of the encoder will be described. Based on VOP rate information 7 that is set externally or in accordance with the encoding condition, the VOP-to-be-encoded determination part 110 determines the VOP to be encoded in the input object images, and outputs the VOP to be encoded to the shape encoding part 111, the motion estimation part 113 and the subtractor 128. The VOP rate 7 mentioned herein refers to a value that represents how many VOPs in each VOL or GOV are to be displayed per second. And the VOP rate information also mentioned herein is a code word corresponding to the VOP rate 7, and it is equivalent to what is called the display speed information in the present invention.

A concrete example of the operation of the VOP-to-be-encoded determination part 110 will be described. When the input object images are 30/sec and the VOP rate 7 is 15/sec, the VOP-to-be-encoded determination part 110 judges that alternate ones of the VOPs contained in the input object images are to be encoded, and outputs every other VOPs to be encoded.

The VOPs specified by the VOP-to-be-encoded determination part 110 as those to be encoded have their shape data encoded for each area with 16 by 16 pixels, which is commonly called an alpha block, and have their texture data encoded for each area with 16 by 16 pixels which is called a macro block.

The shape encoding part 111 encodes the alpha block input thereinto and outputs encoded shape information 112 and locally decoded shape information 109. The encoded shape information 112 is fed to the video signal multiplexing part 126, whereas the locally decoded shape information 109 is input into the motion estimation part 113, the texture encoding part 115 and the texture encoding part 118. The motion estimation part 113 reads reference data 123a from the memory 122 and performs block matching for each macro block to obtain motion information 114. In this case, the motion information is obtained by block matching for only the objects contained in the macro block based on the locally decoded shape information 109.

The motion compensation part 115 reads out of the memory 122 reference data 123b on the position indicated by the motion information 114 and generates a predictive image based on the locally decoded shape information 109. The predictive image 116 created in the motion estimation part 115 is input into the subtractor 128 and the adder 129.

The subtractor 129 calculates the difference between the predictive image 116 and the input macro block to provide a prediction-error image 117.

In the texture encoding part 118 the prediction-error image 117 input thereinto is encoded by a predetermined method prescribed by MPEG-4 to obtain encoded texture information 119 and locally-decoded prediction-error image 120. In this instance, only the objects contained in the block are encoded based on the locally decoded shape information 109. The encoded texture information 119 is sent to the video signal multiplexing part 126, and the locally-decoded prediction-error image 120 is output to the adder 129.

The adder 129 adds the predictive image 116 and the locally-decoded prediction-error image 120 to create a decoded image 121, which is written in the memory 122.

In the header multiplexing part 124 respective pieces of header information are multiplexed, and a bit stream 125 obtained by multiplexing the header information is input into the video signal multiplexing part 126.

The video signal multiplexing part 126 multiplexes the encoded shape information 112, the motion information 114 and the encoded texture information 119 onto the bit stream 125 formed by multiplexing respective header information, and outputs an encoded VOP bit stream.

<figref idref="f0004">Fig. 4</figref> is a block diagram depicting the configuration of the header multiplexing part shown in <figref idref="f0003">Fig. 3</figref>. In <figref idref="f0004">Fig. 4</figref>, reference numeral 1 denotes a VO header multiplexing part, 2 a VOL header multiplexing part, 3 a GOV header e multiplexing selection part, 4 a GOV header multiplexing part, 5 a VOP header multiplexing part, 6 GOV multiplexing information, and 7 VOP rate.

Next, the operation of this embodiment will be described. The VO header multiplexing part 1 creates a bit stream by multiplexing VOP header information, and outputs the bit stream to the VOL header multiplexing part 2.

The VOL header multiplexing part 2 multiplexes VOL header information onto the input bit stream, and outputs the bit stream to the GOV header multiplexing selection part 3.

Based on the GOV multiplexing information 6 indicating whether to perform the multiplexing of the GOV header, the GOV header multiplexing selection part 3 determines the destination of the bit stream fed from the VOL header multiplexing part 2. When the GOV multiplexing information 6 indicates that no multiplexing of the GOV header takes place, the bit stream is output to the VOP header multiplexing part 5, whereas when the GOV multiplexing information 6 indicates that the multiplexing of the GOV header is performed, the bit stream is output to the GOV header multiplexing part 4.

Table 1 exemplifies the abovesaid VOP rate information, showing four kinds of VOP rates. When the VOP rate is 30/sec, "01" is multiplexed. When the VOP to be encoded is the same as the VOP encoded immediately previously, VOP information "00" is multiplexed but the subsequent VOP header information and VOP data information are not multiplexed. When the VOP rate is variable, VOP rate information "11" is multiplexed. That is, the VOP rate 7 indicates whether the VOP rate is fixed or variable, and represents the value of the rate when it is fixed.

A VOP start code multiplexing part 8 in the VOP header multiplexing part 5 outputs to a modulo time base (modulo-time-base) multiplexing part 9 and a VOP time increment (VOP-time-increment) multiplexing part 10 a bit stream obtained by multiplexing a VOP start code onto the input bit stream.

The modulo time base 13 mentioned herein is information that represents what number of seconds will pass until the VOP concerned is displayed after a certain reference time as depicted in <figref idref="f0001">Fig. 5</figref>, and the VOP time increment 14 is information by which the display time defined by the modulo time base is fine-adjusted with an accuracy of 1/1000th of a second as similarly depicted in <figref idref="f0001">Fig. 5</figref>. That is, MPEG-4 permits defining the VOP display time with a precision of 1/1000th of a second.

A management time generating part 12 in the VOP header multiplexing part 5 generates the modulo time base 13 and the VOP time increment 13 based on the VOP rate 7, and outputs the modulo time base 13 to the modulo time base multiplexing part 9 and the VOP time increment 14 to the VOP time increment multiplexing part 10. When the VOP rate 7 represents a variable VOP rate, the modulo time base 13 and the VOP time increment 14 are set independently of the VOP rate 7.

The abovementioned modulo time base multiplexing part 9 multiplexes the modulo time base 13 onto the bit stream provided from the VOP start code multiplexing part, and outputs the multiplexed bit stream to the VOP time increment multiplexing part 10. The VOP time increment multiplexing part 10 multiplexes the VOP time increment 14 fed thereto from the management time generating part 12 onto the bit stream fed from the modulo time base multiplexing part 9, and outputs the multiplexed bit stream to a video information header multiplexing part 11. The video information header multiplexing part 11 multiplexes a video information header onto the bit stream provided thereto from the VOP time increment multiplexing part 10, and outputs the multiplexed bit stream to the video signal multiplexing part 126.

As described above, according to Embodiment 1, since the VOP rate information is multiplexed onto the GOP header, a bit stream can be created which enables the decoder side to determine whether or not to require the decoding of the VOP concerned, or to synthesize a plurality of objects, simply by analyzing only the VOP start code of each VOP header.

It is also possible to define the VOP rate 7 for each VOL and perform encoding and multiplexing of the VOP rate information as shown in <figref idref="f0005">Fig. 6</figref>. In this instance, the VOP rate information is determined for each VOL and is multiplexed in the VOL header multiplexing part 2. Based on this, the modulo time base 13 and the VOP time increment 14 are determined.

As described above, Embodiment 1 has disclosed an example of the image encoding device which encodes images on an objectwise basis and which is provided with encoding means for encoding the images on the basis of predetermined display speed information and multiplexing means for multiplexing the abovesaid predetermined display speed information onto the image signals encoded by the encoding means and for outputting the multiplexed signals.

Furthermore, Embodiment 1 has disclosed an example of the multiplexing means of the type that multiplexes the abovementioned display speed information on an object-by-object basis.

EMBODIMENT 2

Embodiment 2 is directed to another example of the VOP encoder described above in Embodiment 1. The VOP encoder of Embodiment 2 is provided with means for encoding a 1-bit VOP rate flag that indicates as the display speed information whether the object display speed is a fixed or variable speed and the VOP rate that indicates the value of the object display speed, and for multiplying the encoded information onto the bit stream.

When the abovementioned VOP rate flag indicates a variable speed, the VOP rate corresponds to "variable" in Table 1 referred to previously in respect of Embodiment 1, whereas when the VOP rate flag indicates a fixed speed, the VOP rate corresponds to 30/sec or 15/sec in Table 1 mentioned above with respect to Embodiment 1.

<figref idref="f0006">Fig. 7</figref> shows an example of the configuration of the VOP encoder according to Embodiment 2 of the present invention. Reference numeral 1000 denotes a header multiplexing part, 1001 the VOP rate flag, and 1026 the VOP rate. Since the VOP encoder according to Embodiment 2 differs from the VOP encoder described previously in connection with Embodiment 1 only in the configuration and operation of the header multiplexing part 1000 that corresponds to the header multiplexing part 124 of the latter, a description will be given in this respect alone.

<figref idref="f0007">Fig. 8</figref> is a block diagram depicting the configuration of the header multiplexing part 1000 of the VOP encoder part according to Embodiment 2 of the present invention. In <figref idref="f0007">Fig. 8</figref>, reference numeral 1002 denotes a VOL header multiplexing part, and 1003 a VOP header multiplexing part.

Next, the operation will be described.

The VOP header multiplexing part 1 creates a bit stream by multiplexing VO header information, and outputs the thus created bit stream to the VOL header multiplexing part 1002. The VOL header multiplexing part 1002 multiplexes VOL header information onto the input bit stream, and outputs the multiplexed bit stream to the GOV header multiplexing selection part 3. In this case, the VOL rate information and the VOP rate flag are also multiplexed.

Table 3 shows examples of multiplexing of the VOP rate 1026. In this instance, when the VOP rate 1026 is 2/sec, "000" is multiplexed as the VOP rate information; when the VOP rate is 5/sec, "001" is multiplexed; when the VOP rate is 25/sec, "001" is multiplexed; when the VOP rate is 30/sec, "011" is multiplexed; and in the cases of other VOP rates (for example, when the VOP rate is 10/sec), "100" is multiplexed. Incidentally, a decision as to whether to multiplex the VOP rate information is made independently of the VOP flag value described later on. The multiplexing of the VOP rate may also be such as exemplified in Table 4. In this case, when all VOPs are those of exactly the same images in the VOL, the display is regarded as a still picture and "010" is multiplexed as the VOP rate information.

As regards the VOP rate flag, "1" or "0" is multiplexed depending on whether the VOP rate flag indicates a fixed or variable speed. <figref idref="f0008">Fig. 9</figref> depicts an example of the bit stream provided from the VOL header multiplexing part 1002.

Based on the GOV multiplexing information 6 indicating whether to multiplex the GOV header, the GOV header multiplexing selection part 3 determines the destination of the bit stream fed thereto from the VOL header multiplexing part 102. When the GOV multiplexing information 6 does not indicates the multiplexing of the GOV header is performed, the bit stream is output to the VOP header multiplexing part 1003, whereas when the GOV multiplexing information 6 indicates the multiplexing of the GOV header, the bit stream is provided to the GOV header multiplexing part 4.

The GOV header multiplexing part 4 multiplexes the GOV header information onto the input bit stream, and outputs the multiplexed bit stream to the VOP header multiplexing part 1003. <figref idref="f0008">Fig. 10</figref> illustrates the VOP header multiplexing part 1003 in detail. In <figref idref="f0008">Fig. 10</figref>, reference numeral 1004 denotes a management time generating part.

Next, the operation of this embodiment will be described. The management time generating part 1004 generates a modulo time base and a VOP time increment based on the VOP rate 1026 when the input VOP rate flag 1001 indicates a fixed speed, and based on a timer contained in the VOP encoder when the input VOP rate flag 1001 indicates a variable speed. The modulo time base and the VOP time increment thus created are fed to the modulo time base multiplexing part 9 and the VOP time increment multiplexing part 10, respectively.

The VOP time increment multiplexing part 10 multiplexes the VOP time increment onto the input bit stream, and outputs the multiplexed bit stream to the video information header multiplexing part 11. The video information header multiplexing part 11 multiplexes the video information header onto the bit stream provided thereto from the VOP time increment multiplexing part 10, and outputs the multiplexed bit stream to the vide signal multiplexing part 126.

As described above, according to Embodiment 2, since the VOP rate flag and the VOP rate information are multiplexed onto the VOL layer, a bit stream can be created which enables the user to specify his desired VOP in a moment through utilization of the VOP rate flag and the VOP rate on the decoder side--this allows him to determine whether or not to require the decoding of the VOP concerned, or to synthesize a plurality of objects, simply by analyzing only the VOP start code of the corresponding VOP header.

Incidentally, since it is possible to distinguish between variable and fixed speeds even if only the VOP rate flag is multiplexed, the VOP desired to decode can be decoded.

As described above, Embodiment 2 has disclosed an example of the image encoding device which encodes images on an objectwise basis and which is provided with: means for encoding the flag indicating whether the object display speed is fixed or variable; multiplexing means for multiplexing the flag onto the encoded image signal encoded by the encoding means and for outputting the multiplexed signal; encoding means for encoding the images on the basis of predetermined display speed information; and multiplexing means for multiplexing the predetermined display speed information onto the image signals encoded by the encoding means and for outputting the multiplexed signals.

EMBODIMENT 3

Embodiment 3 will be described as being applied to a system wherein an image decoding device for decoding from an encoded bit stream the VOP rate information mentioned previously in connection with Embodiment 1 and for outputting it, that is, an MPEG-4 video decoder (hereinafter referred to as a VOP decoder) is provided for each of a plurality of objects and a plurality of decoded objects are synthesized to reconstruct a pictorial image.

A description will be given first of the configuration and operation of the image decoding device (VOP decoder) in Embodiment 3. Since the operation of the existing VOP decoder is disclosed, for example, in ISO/IEC JTC1/SC29/WG11/N1796, the VOP decoder containing constituents of Embodiment 3 will be described without referring to the existing VOP decoder itself. The VOP decoder in Embodiment 3 is a decoder that is able to decode an encoded bit stream generated by the VOP encoder described previously with reference to Embodiment 1.

<figref idref="f0009">Fig. 11</figref> depicts an example of the internal configuration of the VOP decoder in Embodiment 3 of the present invention. The VOP decoder is supplied with compressed-encoded data composed of texture data and shape data as described previously with reference to Embodiment 1 and shown in <figref idref="f0002">Fig. 2</figref>, and decodes the individual pieces of data. In <figref idref="f0009">Fig. 11</figref>, reference numeral 150 denotes encoded VOP bit stream, 151 a header analysis part, 152 a bit stream with the header information analyzed,153 a video signal analysis part, 154 encoded shape data, 155 a shape decoding part, 156 decoded shape data, 157 encoded texture data, 158 motion information, 159 a motion compensation part, 160 predictive texture data, 161 a texture decoding part, 162 decoded texture data, 164 a memory, and 165 reference data.

Referring to <figref idref="f0009">Fig. 11</figref>, the operation of the decoder will be described in detail. The encoded VOP bit stream 150 is input into the header analysis part 151, wherein the header information is analyzed following a predetermined syntax. The bit stream having the header information analyzed in the header analysis part 151 is fed into the video signal analysis part 153, wherein it is analyzed into the encoded shape data 154, the encoded texture data 157 and the motion information 158. The shape decoding part 155 decodes the encoded shape data input thereinto, and outputs the decoded shape data 156.

The motion compensation part 159 generates the predictive texture data 160 from the reference data 165 in the memory 164 and the motion information 158 provided from the video signal analysis part 153. Based on the encoded texture data 157 and the predictive texture data 160, the texture decoding part 161 reconstructs image data by the method prescribed in MPEG-4, generating the decoded texture data 162. The decoded texture data 162 is used for subsequent VOP decoding, and hence it is written in the memory 164.

<figref idref="f0010">Fig. 12</figref> depicts the internal configuration of the header analysis part 151 that is characteristic of Embodiment 3 of the present invention. In <figref idref="f0010">Fig. 12</figref>, reference numeral 51 denotes a start code analysis part, 52 a VO header analysis part, 53 a VOL header analysis part, 54 GOV header analysis part, 58 VOP rate, and 55 a VOP header analysis part. The header analysis part 151 in Embodiment 3 is characterized in that the GOV header analysis part 54 decodes the VOP rate of VOP contained in the GOV concerned from the bit stream and outputs to the outside. A description will be given later of how to use the VOP rate 58.

The start code analysis part 51 analyzes the start code contained in the encoded VOP bit stream 150 input thereinto. A bit stream is output to the VO header analysis part when the analyzed start code is indicative of VOL, to the VOL header analysis part 53 when the analyzed start code is indicative of VOL, to the GOV header analysis part 54 when the analyzed start code is indicative of GOV, and to the VOP header analysis part 55 when the analyzed start code is indicative of VOP. Incidentally, upon completion of the analysis in the VOP header analysis part 55, the bit stream is output to the video signal analysis part 153.

The VO header analysis part 52 analyzes VO header information from the input bit stream, and outputs the resulting bit stream to the start code analysis part 51. The VOL header analysis part 53 analyzes VOL header information from the input bit stream, and outputs the resulting bit stream to the start code analysis part 51. The GOV header analysis part 54 analyzes GOV header information from the input bit stream, and outputs the resulting bit stream to the start code analysis part 51. At this time, the VOP rate information contained in the GOV header information is decoded and output. The VOP header analysis part 55 analyzes VOP header information from the input bit stream, and outputs the resulting bit stream via the start code analysis part 51 to the video signal analysis part 153.

With the VOP decoder of the above configuration of operation, it is possible to output, for each GOV, the VOP rate of VOPs contained therein. <figref idref="f0011">Fig. 13</figref> illustrates a system that uses this information to synthesize a plurality of objects. In <figref idref="f0011">Fig. 13</figref>, reference numeral 200 denotes an encoded VOP bit stream a, 201 an encoded VOP bit stream b, 202 an encoded VOP bit stream c, 203a a VOP decoder part for decoding the encoded VOP bit stream 200 a200, 203b a VOP decoder part for decoding the encoded VOP bit stream b201, 203c a VOP decoder part for decoding the encoded bit stream c202, 204 a decoded object image a, 205 a decoded object image b, 206 a decoded object image c, 207 VOP rate a, 208 VOP rate b, 209 VOP rate c, 210 a composition part, and 211 a decoded pictorial image. The decoded object image herein mentioned refers to an image that is obtained by combining the decoded shape data 154 and the corresponding decoded texture data 162 for each of VOPs and then integrating such combined pieces of data for each group of VOPs (for example, GOV or VOL).

The encoded VOP bit streams a200 to c202 are decoded by the VOP decoder parts 203a to 203c corresponding thereto, respectively, by which the decoded VOP images a204 to c206 are generated. At this time, the VOP decoder parts decode the corresponding VOP rate a207 to c209, and output them to the composition part 210. Based on the VOP rate information a207 to c209, the composition part 210 determines the time of the frame where to synthesize the decoded VOP images in the decoded image 211, and maps them into the frame corresponding to the determined time. Let it be assumed, for example, that the decoded image 211 is displayed at a rate of 30 video object planes per sec (which corresponds to a ordinary TV signal display speed). Furthermore, assume the following situations.

The decoded VOP image a204 is displayed at a rate of 5/sec (that is, the VOP rate a207 indicates the 5/sec rate).

The decoded VOP image b205 is displayed at a rate of 10/sec (that is, the VOP rate indicates the 10/sec rate).

The decoded VOP image c206 is displayed at a rate of 15/sec (that is, the VOP rate c209 indicates the 15/sec rate).

In this instance, the decoded VOP images a204 to c206 are all mapped into the first image frame at each second in the decoded image 211; the decoded VOP image a204 is mapped into every five image frames including the first at each second; the decoded VOP image b205 is mapped into every 10 image frames including the first at each second; and the decoded VOP image c206 is mapped into every 15 images frames including the first at each second. By this, it is possible to display a pictorial image with a plurality of objects synthesized in the image frames in accordance with their display speeds.

As described above, by using VOP decoder which decodes the encoded bit stream having the VOP rate encoded in the GOV layer, a system which synthesizes a plurality of object into a reconstructed image can be implemented with a simple structure.

The VOP rate may also be encoded for each VOL at the image encoding device side. In this case, it is possible, at the image decoding device side, to decode the VOP rate encoded for each VOL and easily synthesize a plurality of objects for each VOL as described above.

While Embodiment 3 employs the VOP decoder as a system for synthesizing a plurality of objects, it is also feasible to use only one VOP decoder for a system that decodes only one object to reconstruct an image.

As described above, according to Embodiment 3, the image decoding device which decodes the bit stream encoded from an image on an object-by-object basis is provided with display speed information decoding means for decoding display speed information from the encoded bit stream and control means for controlling the reconstruction of the image encoded on the object-by-object basis through utilization of the display speed information decoded by the display speed information decoding means.

In Embodiment 3 the display speed information decoding means has been described to decode the display speed information object by object.

EMBODIMENT 4

Embodiment 4 is directed to another modification of the VOP decoder described above in Embodiment 3. The VOP decoder according to Embodiment 4 has a function of specifying the VOP to be decoded on the basis of the value of the VOP rate that the decoder assumes.

Since the VOP decoder of Embodiment 4 differs from Embodiment 2 only in the configuration and operation of the header analysis part 151, a description will be given only in this respect.

<figref idref="f0012">Fig. 14</figref> is a block diagram illustrating the configuration of the header analysis part of the VOP decoder part according to Embodiment 4, in which the VOP rate at the encoder side and the VOP rate at the decoder side do not match. In <figref idref="f0012">Fig. 14</figref>, reference numeral 59 denotes a VOP-to-be-decoded selection part, which compares a VOP rate from the GOV header analysis part 54 and a VOP rate assumed at the decoder side, and outputs VOP select information 62. And the VOP header analysis part 55 has a counter 60 has a counter part 60 in addition to a time management information header analysis part 56 and a video information header analysis part 57.

Next, the operation of this embodiment will be described. The VOP-to-be-decoded selection part 59 outputs to the counter part 60 of the VOP header analysis part 55 the VOP select information that indicates information about the VOP to be decoded according to the result of comparison between the VOP rate 58 analyzed in the GOV header analysis part 54 and the VOP rate 61 assumed at the decoder side. The counter part 60 uses the VOP select information 62 to determined whether to decode the VOP header information that follows the VOP start code contained in the input bit stream.

More specifically, when the VOP rate 58 analyzed in the GOV header analysis part 55 is 30 planes/sec and the VOP rate assumed at the decoder side is 15 planes/sec, the VOP select information 62 indicating that every other VOPs are analyzed is output to the counter part 60 in the VOP header analysis part 55. The counter part 60 first counts every VOP header input thereinto by a counter 60a.

Then, based on the count value input thereinto from the counter 60a and the VOP rate select information 62 from the VOP-to-be-decoded selection part 59, decision means 60b decides whether the input VOP needs to be analyzed. When it is decided that the input VOP needs to be analyzed, the input bit stream is output to the time management information header analysis part 56. When it is decided that the input VOP need not be analyzed, the input bit stream is output to the start code analysis part 51.

A concrete example will be described below. When the VOP rate select information 62 is one that one VOP needs to be analyzed for every three VOPs, the decision means 60b judges that the VOP needs to be analyzed for which the count value from the counter 60a can be divided by 3 without a remainder, and that the VOP need not be analyzed for which the count value from the counter 60a is divided by 3, with a remainder of 1 or 2.

Incidentally, while the VOP decoder of Embodiment 4 has been described to be adapted for use in the case where the VOP rate information is contained in the GOV header, the VOP rate information may also be contained in the VOL header as described previously with reference to Embodiment 2. In such an instance, the VOL header analysis part 300 needs only to be equipped with the function of decoding the VOP rate information.

Moreover, the VOP decoder of Embodiment 4 can be used not only in a system which synthesizes a plurality of objects but also in a system which decodes and reconstructs only one object.

As described above, the decoder according to Embodiment 4 has control means which is provided with: decoding time specifying means for specifying the time when to decode an object on the basis of the object display information decoded by the display speed information decoding means and the object display speed information preset in the decoding device; and decoding means for decoding the object at the decoding time specified by the decoding time specifying means.

EMBODIMENT 5

Embodiment 5 will is directed to another example of the VOP decoder described above in Embodiment 4. The VOP decoder according to Embodiment 5 is equipped with a function of specifying a VOP to be decoded on the basis of: the VOP rate flag indicating whether the object display speed is fixed or variable; the VOP rate information indicting the object display speed; externally-set display control information indicating time information externally set by a user; and a time code.

Since the VOP decoder according to Embodiment 5 differs, as shown in <figref idref="f0014">Fig. 16</figref>, from Embodiment 3 only in the configuration and operation of a header analysis part 1005 corresponding to the header analysis part 151 of the VOP decoder of the latter, a description will be given in this respect alone.

<figref idref="f0015">Fig. 17</figref> is a block diagram illustrating the configuration of the header analysis part 1005 of the VOP decoder part according this embodiment. In <figref idref="f0015">Fig. 17</figref>, reference numeral 1006 denotes a VOL header analysis part, 1007 a GOV header analysis part, 1008 a VOP header analysis part, 1009 an externally-set display control information, 1010 a VOP rate flag, and 1011 a time code. Incidentally, the externally-set display control information 1009 may be information indicating absolute time or VOP select information indicating the number of VOPs from which one VOP to be decoded is selected.

Next, the operation of this embodiment will be described. The start code analysis part 51 analyzes the start code contained in the input encoded VOP bit stream. The start code analysis part outputs the bit stream to the VO header analysis part 52 when the analyzed start code indicates VO, to the VOL header analysis part 1006 when the analyzed start code indicates VOL, to the GOV header analysis part 1077 when the analyzed start code indicates GOV, and to the VOP header analysis part 1008 when the analyzed start code indicates VOP. Incidentally, the bit stream is output to the video signal analysis part 153 after completion of the analysis in the VOP header analysis part 1008.

Next, the VO header analysis part 52 analyzes the VO header, the VOP rate 58 and the VOP rate flag 1011 contained in the input bit stream, and outputs the analyzed bit stream to the start code analysis part 51 and, at the same time, outputs the VOP rate 58 to the composition part 210 and the VOP header analysis part 1008 and the VOP rate flag 1010 to the VOP header analysis part 1008.

The GOV header analysis 1007 analyzes the GOV header contained in the input bit stream, and outputs the analyzed bit stream to the start code analysis part 51 and, at the same time, outputs the time code 1011 contained in the analyzed GOV header to the VOP header analysis part 1008.

<figref idref="f0016">Fig. 18</figref> is a block diagram illustrating the VOP header analysis part 1008 in detail. Reference numeral 1012 denotes a VOP-to-be-decoded determining part (1), which has a counter part 1012a and decision means 1012b. Reference numeral 1013 denotes a modulo time base analysis part, 1014 a VOP time increment analysis part, 1015 a VOP-to-be-decoded determining part (2), and 1016 a VOP-to-be-decoded determining method select part.

Next, the operation of this embodiment will be described. The VOP-to-be-decoded determining method select part 1016 uses the VOP rate flag 1010 to determine the destination of the input bit stream. When the VOP rate flag 1010 indicates a fixed speed, the VOP-to-be-decoded determining part (1) 1012 is selected as the destination of the bit stream, and when the VOP rate flag 1010 indicates a variable speed, the modulo time base analysis part 1013 is selected.

A description will be given first of the case where the VOP rate flag 1010 indicates a fixed speed. The counter part 1012a in the VOP-to-be-decoded determining part (1) 1012 increments its count value upon each input of the bit stream into the VOP header analysis part 1006 when the VOP start code is detected in the start code analysis part 51, and outputs the count value and the bit stream to the decision means 1012b.

Then the decision means 1012b decides whether the VOP to be decoded needs to be decoded. The operation of the decision means 1012b will be described in respect of first and second cases where the externally-set display control information 1009 is provided as absolute time and where the externally-set display control information 1009 is provided as VOP select information.

(First Case)

Based on the count value and the VOP rate fed thereto from the counter part 1012a and the time code 1011, the decision means calculates the absolute time that the VOP candidate for decoding has. For example, in the case where the count value is 4, the VOP rate is 2/sec and the absolute time is 0h10m0sec0msec, the absolute time that the VOP candidate for decoding has is calculated to be 0h10m02sec0msec. If the thus calculated absolute time of the VOP candidate for decoding and the externally-set display control information 1009 are equal to each other, it is decided that decoding needs to be done.

On the other hand, when they are not equal, the absolute time of the next VOP candidate for decoding is calculated. This is intended to make comparison between the absolute time of the next VOP candidate for decoding and the absolute time of the current VOP candidate for decoding so as to ensure decoding the VOP of the absolute value closer to the externally-set display control information 1009. The absolute time of the next VOP candidate for decoding is calculated from the already calculated absolute time of the current VOP candidate for decoding and the VOP rate 58. When this calculated value is smaller or equal to the externally-set display control information 1009, it is decided that the next VOP candidate for decoding is to be decoded, and the current VOP candidate for decoding is not decoded. When the calculated value exceeds the externally-set display control information 1009, any of the following methods may be chosen.

Decode the current VOP candidate for decoding;

Decode the next VOP candidate for decoding (=not decode the current VOP candidate for decoding);

Decode the VOP of an absolute time which has a small difference between it and the externally-set display control information 1009, that is, which is close to the externally-set display control information 1009.

(Second Case)

This is the case where the display speed is controlled at the VOP decoder side; for example, the user is allowed to determine the display speed or designate the optimum display speed according to CPU resources.

Next, the operation in this case will be described. Let it be assume that the VOP select information indicating the necessity for decoding one for every three VOPs. In this instance, the decision means 1012b judges that decoding needs to be done when the count value fed thereto from the counter part 1012a can be divided by 3 without a remainder and that decoding need not be done when the count value from the counter part 1012a is divided by 3 with a remainder 1 or 2.

In either of the first and second cases, when it is judged that the VOP candidate for decoding must be decoded, the decision means outputs a bit stream to the modulo time base analysis part 1013, and to the start code analysis part 51 when it is judged that no decoding is necessary. The modulo time base analysis part 1013 analyzes the modulo time base, and outputs a bit stream to the VOP time increment analysis part 1014.

The VOP time increment analysis part 1014 analyzes the VOP time increment, and outputs a bit stream to the video information header analysis part 57. The video information header analysis part 57 analyzes the video information header, and outputs a bit stream to the start code analysis part 51.

Next, a description will be given of the case where the VOP rate flag 1010 indicates a variable speed. The modulo time base analysis part 1013 analyzes the modulo time base, and outputs a bit stream to the VOP time increment analysis part 1014. The VOP time increment analysis part 1-14 analyzes the VOP time increment, and outputs a bit stream to the VOP-to-be-decoded determining part (2) 1015.

Based on the modulo time base analyzed in the modulo time base analysis part 1013, the VOP time increment analyzed in the VOP time increment analysis part 1014 and the time code 1011, the VOP-to-be-decoded determining part (2) 1015 generates the absolute time of the VOP candidate for decoding, and based on the generated absolute time and the externally-set display control information 1009, determines whether the VOP candidate for decoding needs to be decoded. When it is determined that the VOP needs to be decoded, a bit stream is output to the video information header analysis part 57, and to the start code analysis part 51 when it is judged that no decoding is necessary. The video information header analysis part 57 analyzes the video information header, and outputs a bit stream to the start code analysis part 51.

As described above, according to Embodiment 5, since the bit stream with the encoded VOP rate flag and VOP rate is multiplexed onto the VOL layer, it is possible for the user to specify his desired VOP in a moment through utilization of the VOP rate flag and the VOP rate--this allows him to determine whether the VOP concerned needs to be decoded, or to synthesize a plurality of objects, simply by analyzing only the VOP start code contained in the corresponding VOP header information.

Incidentally, when the VOPs contained in the encoded VOP bit stream input into the VOP decoder are all intra-encoded, the user can specify his desired VOP in a moment and cause it to be displayed.

As described above, the decoder according to Embodiment 5 is characterized by control means which controls the image reconstruction by specifying the display time of the image at each time for decoding on the basis of the display speed information when the display speed identification information decoded by the display speed information decoding means indicates a fixed speed and on the basis of display time information multiplexed for each image at each time in the case where the display speed identification information indicates a variable speed.

EMBODIMENT 6

Embodiment 6 is directed to another example of the VOP decoder described above in Embodiment 5. The VOP decoder according to Embodiment 6 has a function of specifying the VOP to be decoded on the basis of the VOP rate flag indicating whether the object display speed is fixed or variable, the VOP rate indicating the object display speed, the externally-set display control information externally set by the user, and the time code.

<figref idref="f0017">Fig. 19</figref> is a diagram depicting the header analysis part in Embodiment 6 of the present invention. Since the VOP decoder of Embodiment 6 differs from Embodiment 5 only in the configuration and operation of the VOL header analysis part 1006 and VOP header analysis part 1008, a description will be given in this respect alone.

A VOL header analysis part 1017 analyzes the VOL header, the VOP rate information and the VOP rate flag contained in the bit stream input thereinto, and outputs the analyzed bit stream to the start code analysis part 51 and the VOP rate flag 1010 to a VOP header analysis part 1018; at the same time, it outputs the VOP rate 58 to the VOP header analysis part 1016 when the analyzed VOP rate information indicates any fixed rate value (for example, the VOP rate indicated by VOP rate information "100" in Table 3), and the VOP rate 58 to the VOP header analysis part 1018 and the composition part 210 when the analyzed VOP rate information indicates a particular value (for example, the VOP rates indicated by VOP rate information "000", "001", "010" and "011" in Table 3).

<figref idref="f0018">Fig. 20</figref> is a diagram depicting the VOP header analysis part 1018 in detail. Reference numeral 1025 denotes a VOP-to-be-decoded determining method select part, and 1019 a VOP-to-be-decoded determining part (3), which has a counter part 1919a, a count value decision part 1019b and decision means 1019c. Reference numeral 1020 denotes a time information holding part, 1021 a VOP rate information calculation part, 1022 a VOP rate information holding part, 1023 a modulo time base analysis part, and 1024 a VOP time increment analysis part.

Based on the VOP rate flag 1010 and the VOP rate 58 input thereinto, the VOP-to-be-decoded determining method select part 1025 selects the destination of the input bit stream. More specifically, when the VOP rate flag 1010 indicates a fixed speed and the VOP rate 58 indicates some fixed rate value, the VOP-to-be-decoded determining part (3) 1019 is selected as the destination. When the VOP rate flag 1010 indicates a variable speed, the operation described previously in Embodiment 5 is performed, which will not be described again. When the VOP rate flag 1010 indicates a fixed speed and the VOP rate 59 a particular value, the bit stream is output to the VOP-to-be-decoded determining part (1) 1012. In this instance, the VOP-to-be-decoded determining part (1) 1012 and the parts following it perform the same operations as described previously in Embodiment 5; so, no description will be repeated.

Accordingly, a description will be given below of the case where the VOP rate flag 1010 indicates a fixed speed and the VOP rate 58 some fixed rate value.

The counter part 1019a in the VOP-to-be-decoded determining part (3) 1019 increments its count value whenever the VOP start code is detected in the start code analysis part 51 and a bit stream is fed into the VOP header analysis part 1018, and it outputs the count value and the bit stream to the count value decision part 1019b. The count value decision part 1019b outputs the bit stream and the count value to the modulo time base analysis part 1023 when the count value indicates a first or second VOP, and in the other cases, it outputs the bit stream and the count value to the decision means 1019c.

The modulo time base analysis part 1023 analyzes the modulo time base and, when the input count value indicates the first VOP, outputs the modulo time base to the time information holding part 1020 and to the VOP rate information calculation part 1021 when the input count value indicates the second VOP, while at the same time it outputs the bit stream and the count value to the VOP time increment analysis part 1024.

The VOP time increment analysis part 1024 analyzes the VOP time increment and, when the input count value indicates the first VOP, outputs the VOP time increment to the time information holding part 1020 and to the VOP rate information calculation part 1021 when the input count value indicates the second VOP, while at the same time it outputs the bit stream to the video information header analysis part 57. The video information header analysis part 57 analyzes the video information header, and outputs the bit stream to the start code analysis part 51.

The time information holding part 1020 holds the modulo time base and the VOP time increment input thereto. Upon input thereto of the modulo time base and the VOP time increment for the second VOP, the VOP rate information calculation part 1021 reads thereinto from the time information holding part 1020 the modulo time base for the first VOP and the VOP time increment similarly for the first VOP, then calculates the VOP rate based on them, and outputs the VOP rate to the VOP rate information holding part 1022. A concrete example of the calculation of the VOP rate in the VOP rate information calculation part 1021 will be described below in connection with the case where the VOP time increment is expressed with a 6-bit accuracy.

In the case where the modulo time base for the first VOP is "10", the VOP time increment for the first VOP is "000000" (that is, the time information about the first VOP is 1.0 sec), the modulo time base for the second VOP is "10" and the VOP time increment for the second VOP is "100000" (that is, the time information about the second VOP is 1.5 sec), the difference between the time information about the both is 0.5 sec. This means that the VOP to be decoded exists every 0.5 sec, that is, the VOP rate is 2/sec (which corresponds to VOP rate information "000" in Table 3).

Even when the VOP rate 58 is not multiplexed, if only the VOP rate flag 1010 is multiplexed, it can be judged therefrom that a fixed rate is indicated, and consequently, such operation as described above can be carried out.

The VOP rate information holding part 1022 holds the VOP rate input thereto, and outputs the VOP rate to the composition part 210. The operation of the decision means 1019a will be described below in connection with first and second cases where the externally-set display control information 1009 is provided as absolute time and where the externally-set display control information is provided as the VOP rate.

(First Case)

Based on the count value fed thereto from the count value decision part 1019b and the VOP rate provided from the VOP rate information holding part 1022, the decision means 1019c calculates the absolute time that the VOP candidate for decoding has. When the thus calculated absolute time of the VOP candidate for decoding and the externally-set display control information 1009 are equal to each other, it is judged that decoding needs to be done.

On the other hand, when they are not equal, the absolute time of the next VOP candidate for decoding is calculated. This is intended to make comparison between the absolute time of the next VOP candidate for decoding and the absolute time of the current VOP candidate for decoding so as to ensure decoding the VOP of the absolute value closer to the externally-set display control information 1009. The absolute time of the next VOP candidate for decoding is calculated from the already calculated absolute time of the current VOP candidate for decoding and the VOP rate 58. When this calculated value is smaller or equal to the externally-set display control information 1009, it is decided that the next VOP candidate for decoding is to be decoded, and the current VOP candidate for decoding is not decoded. When the calculated value exceeds the externally-set display control information 1009, any of the following methods may be chosen.

Decode the current VOP candidate for decoding;

Decode the next VOP candidate for decoding (=not decode the current VOP candidate for decoding);

Decode the VOP of an absolute time which has a small difference between it and the externally-set display control information 1009, that is, which is close to the externally-set display control information 1009.

(Second Case)

When the VOP rate derived from the externally-set display control information 1009 is 2/sec and the VOP rate indicated by the VOP rate information fed from the VOP rate information holding part 1022 is 4/sec, the VOP information indicating the number of VOPs from which one VOP is selected for decoding becomes information that every other VOPs need to be decoded. In this instance, the decision means 1019c judges that the VOP for which the count value input thereto from the count value decision part 1019b can be divided by 2 without a remainder is to be decoded, and that the VOP for which the count value from the count value decision part 1019b is divided by 2 but with a remainder of 1 is not to be decoded.

In both of the first and second cases, when it is decided that the VOP candidate for decoding needs to be decoded, the bit stream is output to the modulo time base analysis part 1013, and when it is decided that no decoding is needed, the input bit stream is output to the start code analysis part 51. The modulo time base analysis part 1013 analyzes the modulo time base, and outputs the bit stream to the VOP time increment analysis part 1014; the VOP time increment analysis part 1014 analyzes the VOP time increment, and outputs the bit stream to the video information header analysis part 57; and the video information header analysis part 57 analyzes the video information header, and outputs the bit stream to the start code analysis part 51.

As described above, according to Embodiment 6, since the bit stream with the encoded VOP rate flag and VOP rate is multiplexed onto the VOL layer, and since the VOP rate information is calculated from the absolute times of the first and second VOPs when the VOP rate flag indicates a fixed speed, it is possible for the user to specify his desired VOP in a moment through utilization of the VOP rate flag and the VOP rate-this allows him to determine whether the VOP concerned needs to be decoded, or to synthesize a plurality of objects with ease, simply by analyzing only the VOP start code contained in the corresponding VOP header information with respect to an arbitrary fixed VOP rate.

Incidentally, when the VOPs contained in the encoded VOP bit stream input into the VOP decoder are all intra-encoded, the user can specify his desired VOP in a moment and cause it to be displayed.

As described above, the decoder according to Embodiment 6 is characterized by control means which controls image reconstruction by specifying the display time of the image at each time for decoding on the basis of the display speed information multiplexed for each image at each time in the case where the display speed identification information decoded by the display speed information decoding means indicates a fixed speed and the fixed speed is a value not represented by the display speed information.

EMBODIMENT 7

Embodiment 7 is directed to another example of the VOP encoder described previously in Embodiment 1. The VOP encoder of Embodiment 7 has a function of adding, for each VOL, the time code that defines the absolute display time of each VOP contained in the VOL concerned.

The time code mentioned herein is time information disclosed in IEC standard publication 461 for "time and control codes for video tape recorders", which is information that defines the display time of an image at each time forming a moving picture (a frame in MPEG-2 and a VOP in MPEG-4) with an accuracy of hour/minute/second. For example, in the case of performing video editing on a frame-by-frame basis by commercial video editor, the addition of this information to each frame makes it possible to access a desired frame simply by designating the value of the time code.

Since the VOP encoder of Embodiment 7 differs from the encoder of Embodiment 1 only in the configuration and operation of the header multiplexing part 124, a description will be given in this respect alone.

<figref idref="f0019">Fig. 21</figref> is a block diagram illustrating the configuration of the header multiplexing part of the VOP encoder part according to Embodiment 7 of the present invention; the parts identical with those in Embodiments 1 of <figref idref="f0004">Fig. 4</figref> are marked with the same reference numerals as in the latter, and no description will be repeated.

Next, the operation of this embodiment will be described. The bit stream with the VO header information multiplexed thereon in the VO header multiplexing part 1 is input into the VOL header multiplexing part 2. The VOL header multiplexing part 2 multiplexes on the input bit stream the VOL header information and a time code 18 forming the basis for time management, and outputs the bit stream to the GOV header multiplexing selection part 3.

The GOV header multiplexing selection part 3 determines the destination of the input bit stream from the VOL header multiplexing part 2 on the basis of the GOV multiplexing information 6 indicating whether to perform the multiplexing of the GOV header. When the GOV multiplexing information 6 indicates that no multiplexing of the GOV header is performed, the bit stream is output to the VOP header multiplexing part 5, whereas when the GOV multiplexing information 6 indicates that the multiplexing of the GOV header is performed, the bit stream is output to the GOV header multiplexing part 4. In this instance, the GOV header multiplexing part 4 multiplexes the GOV header information on the bit stream fed from the GOV header multiplexing selection part 3, and outputs the bit stream to the VOP header multiplexing part 5.

The VOP header multiplexing part 5 multiplexes the VOP start code, the time management information header and the video information header onto the input bit stream, and outputs it to the video signal multiplexing part 126 (see <figref idref="f0003">Fig. 3</figref>).

Incidentally, the operations of the video signal multiplexing part 126 and the parts following it are the same as described above.

As described above, according to Embodiment 7, since the time code is multiplexed onto the VOL header which is always encoded in MPEG-4, it is possible to form a bit stream which permits the creation of a pictorial image composed of a plurality of objects on the basis of the time code. Moreover, in the case of performing edits while decoding the encoded bit stream according to Embodiment 7 by a commercial object-by-object video editor, a VOP at an arbitrary time of objects can freely be accessed randomly at all times. These effects provide increased flexibility in image synthesis.

Incidentally, while the encoder of Embodiment 7 has been described to add the time code for each VOL, the encoder may also be configured to add the time code information for each VOP. This could be implemented by such a configuration as shown in <figref idref="f0020">Fig. 22</figref> in which the time code 18 defining the absolute display time of each VOP is input into and multiplexed by a VOP header multiplexing part 301.

Furthermore, Embodiment 7 has been described to involve the encoding of the VOP rate, but it is a matter of course that the multiplexing of the time is independent of the VOP rate, and even when the VOP rate is not encoded, the same effects as mentioned above are obtainable.

As described above, the image encoding device of Embodiment 7 which encodes images on the object-by-object basis is provided with absolute time multiplexing means by which information representing the absolute time of each object is multiplexed onto an encoded image signal.

EMBODIMENT 8

Embodiment 8 will be described in connection with a system which a plurality of VOP decoders each of which decodes and outputs a time code from the VOL header in the encoded bit stream and synthesizes a plurality of decoded objects into an image.

A description will be given first of the configuration and operation of the VOP decoder in Embodiment 8. The internal configuration of the VOP decoder in Embodiment 8 is depicted in <figref idref="f0021">Fig. 23</figref>. Since this decoder differs from the VOP decoder of Embodiment 2 only in the configuration and operation of a header analysis part 302, a description will be given below in this respect alone. The header analysis part 302 has a function of decoding and outputting the time code in the VOL header.

<figref idref="f0022">Fig. 24</figref> illustrates the internal configuration of the header analysis part 302. In <figref idref="f0022">Fig. 24</figref>, reference numeral 303 denotes a VOL header analysis part. The start code analysis part 51 analyzes the start code contained in the input encoded VOP bit stream 150. The start code analysis part outputs the bit stream to the VO header analysis part 52 when the analyzed start code indicates VO, to the VOL header analysis part 303 when the analyzed start code indicates VOL, to the GOV header analysis part 54 when the analyzed start code indicates GOV, and to the VOP header analysis part 55 when the analyzed start code indicates VOP. Incidentally, upon completion of the analysis in the VOP header analysis part 55, the bit stream is output therefrom to the video signal analysis part 153.

The VO header analysis part 52 analyzes the Vo header contained in the input bit stream, and outputs the analyzed bit stream to the start code analysis part 51. The VOL header analysis part 303 analyzes the VOL header information in the input bit stream, and outputs the analyzed bit stream to the start code analysis part 51. In this case, the time code 64 contained in the VOL header information is decoded and output. The GOV header analysis part 54 analyzes the GOV header information in the input bit stream, and outputs the analyzed bit stream to the start code analysis part 51. The VOP header analysis part 55 analyzes the VOP header information in the input bit stream, and outputs the analyzed bit stream via the start code analysis 51 to the video signal analysis part 153.

With the VOP decoder of the above configuration and operation, it is possible to output, for each VOL, the absolute display time of each VOP contained therein. In <figref idref="f0023">Fig. 25</figref> there is depicted a system which uses this information to synthesize a plurality of objects.

In <figref idref="f0023">Fig. 25</figref>, reference numeral 400 denotes an encoded VOP bit stream a, 401 an encoded VOP bit stream b, 402 an encoded bit stream c, 403 a VOP decoder part for decoding the encoded VOP bit stream a400, 403b a VOP decoder part for decoding the encoded VOP bit stream b401, 403c a VOP decoder part for decoding the encoded VOP bit stream c402, 404 a decoded object image c, 405 a decoded object image b, 406 a decoded object image c, 407 a time code a, 408 a time code b, 409 a time code c, 410 a composition part, and 411 a decoded image. What is intended to mean by the decoded object image is an image obtained by combining the decoded shape data 156 and the corresponding decoded texture data 162 for each of VOPs and then integrating such combined pieces of data for each group of VOPs (for example, GOV or VOL).

The encoded VOP bit stream a400 to the encoded VOP bit stream c402 are decoded by the VOP decoder parts 403a to 403c corresponding thereto, respectively, by which the decoded VOP images a404 to c406 are generated. At this time, the VOP decoder parts decode the corresponding time codes a407 to c409, and output them to the composition part 210. Based on the time codes a407 to c409, the composition part 210 determines the time of the frame of the decoded image 411 where to synthesize the decoded VOP of each decoded object image, and maps them into the frame corresponding to the determined time. For example, assume the following situations. <ul id="ul0001" list-style="none"><li>* The composition part has a time code generation capability, and determines the absolute display time of each image frame to synthesize.</li><li>* Assume that 01:00:00 is decoded as the time code of the first VOP of the decoded object image a404, where 01:00:00 represents (hour):(minute):(second).</li><li>*Assume that 01:00:10 is decoded as the time code of the first VOP of the decoded object image b405.</li><li>* Assume that 01:01:00 is decoded as the time code of the first VOP of the decoded object image c406.</li></ul>

Assuming that the time code of the first image frame of the decoded image 411 defined in the composition part 410 is 01:00:00, the decoded object image a404 is mapped into the first frame of the decoded image 411, the decoded object image b405 is mapped 10 seconds after the first frame of the decoded image 411, and the decoded object image c406 is mapped one minute after the first frame of the decoded image 411; thus, an object of displaying the decoded objects can be performed. By this, it is possible to display a pictorial image with a plurality of video objects synthesized in the image frames in correspondence to the reference absolute times.

As described above, by using the VOP decoder which decodes the encoded bit stream having the time code encoded in the GOV layer, a system which synthesizes a plurality of object into a reconstructed image can be implemented with a simple structure.

The time code may also be encoded for each VOL at the image encoding device side as depicted in <figref idref="f0024">Fig. 26</figref>. In this case, it is possible, at the image decoding device side, to decode the time code encoded for each VOL and synthesize a plurality of objects for each VOL as described above.

It is also possible to configure such a VOP decoder as shown in <figref idref="f0025">Fig. 27</figref> in which an encoded bit stream with the VOP rate multiplexed thereon are input into the VOL header, together with the time code. In this instance, since the absolute display time of the first VOP of the VOL is determined by the time code and then the absolute display time of each VOP can easily be detected from the VOP rate, it is feasible to configure a system that synthesizes a plurality of objects with more ease.

While Embodiment 8 employs the VOP decoder as a system for synthesizing a plurality of objects, it is also possible to use only one VOP decoder in a system that decodes only one object to reconstruct an image.

As described above, according to Embodiment 8, the image decoding device which decodes the bit stream encoded from an image on an object-by-object basis is provided with absolute time analysis means for analyzing, for each object, information indicating the absolute time therefor and means for reconstructing the image processed on the object-by-object basis through utilization of the information indicating the absolute time analyzed by the absolute time analysis means.

EMBODIMENT 9

Embodiment 9 will be described in connection with an improved modulo time base encoding method and a VOP encoder therefore which are used to represent the modulo time base (corresponding to first time information) and the VOP time increment (corresponding to second time information) which are now used in MPEG-4.

A description will be given first of the method for representing the modulo time base 20 in MPEG-4.

As described previously in Embodiment 1, the value of the modulo time base is information that indicates what number of seconds will pass until the VOP concerned is displayed after a certain reference time as shown in <figref idref="f0001">Fig. 5</figref>, and the information expresses the number of seconds in terms of the number of bits of the value "1." The end of the data is clearly indicated by adding the value "0." That is, when the display is provided after 5 seconds, the information becomes "111110." With this method, when the reference time does not change at all, the amount of information of the modulo time base increases infinitely. At present, MPEG-4 defines the reference time by the time code that is multiplexed onto the GOV header, but since the GOV header is a option, the GOV header need not always be encoded under MPEG-4 prescriptions. That is, there is a fear that the value of the modulo time base becomes longer limitlessly unless the GOV header appears. Embodiment 9 implements an encoder that obviates such a problem in encoding the data of the modulo time base.

Embodiment 9 requires modifying only the configuration and operation of the header multiplexing part 124 of the VOP encoders described so far, a description will be focused on this part alone.

<figref idref="f0026">Fig. 28</figref> illustrates the internal configuration of the header multiplexing part 124 in Embodiment 9 of the present invention. Reference numeral 500 denotes a VOP header multiplexing part, 19 a bit length calculating part, 20 a modulo time base, 21 a shifted modulo time base, 22 an information bit indicating a repeat count, and 501 a modulo time base multiplexing part.

Next, the operation of this embodiment will be described. The bit stream with the VO header information multiplexed thereon in the VO header multiplexing part 1 is input into the VOL header multiplexing part 2. The VOL header multiplexing part 2 multiplexes the VOL header information onto the input bit stream, and outputs the multiplexed bit stream to the GOV header multiplexing selection part 3.

The GOV header multiplexing selection part 3 determines the destination of the bit stream from the VOL header multiplexing part 2 on the basis of the GOV multiplexing information 6 indicating whether to perform multiplexing of the GOV header. When the GOV multiplexing information 6 indicates that no multiplexing of the GOV header is performed, the bit stream is output to the VOP header multiplexing part 5, whereas when the GOV multiplexing information 6 indicates that the multiplexing of the GOV header is performed, the bit stream is output to the GOV multiplexing part 4. In this case, the GOV header multiplexing part 4 multiplexes the GOV header information onto the bit stream from the GOV header multiplexing selection part 3, and outputs the multiplexed bit stream to the VOP header multiplexing part 5.

The VOP start code multiplexing part 8 in the VOP header multiplexing part 500 multiplexes the VOP start code onto the input bit stream, and outputs the multiplexed bit stream to the modulo time base multiplexing part 501. The bit length calculating part 19 in the VOP header multiplexing part 500 compares the bit length of the modulo time base 20 and a present positive threshold value; when the bit length of the modulo time base 20 is longer than the threshold value, the modulo time base 20 is left-shifted repeatedly by the length of the threshold value until the bit length of the modulo time base becomes shorter than the threshold value, and the modulo time base 21, which is the resulting bit string, and the information bit 22, which indicates the shift-repeat count, are output. The information bit 22 indicating the shift-repeat count may be provided as a binary number that expresses the shift-repeat count by a predetermined number of bits, or as a variable bit length that expresses the shift-repeat count by a variable-length code.

A concrete example of the operation in the bit length calculation part 19 will be described below. With the above said threshold value set at 4, if the modulo time base 20 is "1111111110," the shift-repeat count is two and the shifted modulo time base 21 is "10." If expressed by a fixed-length two bits, the information bit 22 indicating the shift-repeat count is "10." The modulo time base multiplexing part 501 in the VOP header multiplexing part 500 multiplexes onto the bit stream from the VOP start code multiplexing part 8 the shifted modulo time base 21 and the information bit 22 indicating the shift-repeat count, and outputs the multiplexed bit stream to the VOP time increment multiplexing part 10.

The VOP time increment multiplexing part 10 multiplexes the VOP time increment onto the bit stream from the modulo time base multiplexing part 10, and outputs the multiplexed bit stream to the video information header multiplexing part 11. The video information header multiplexing part 11 multiplexes the video information header onto the bit stream from the VOP time increment multiplexing part 10, and outputs the multiplexed bit stream to the video signal multiplexing part 26.

As described above, according to Embodiment 9, the modulo time base is expressed by two kinds of information bits (the shifted modulo time base and the information bit indicating the shift-repeat count), and these two kinds of information bits are multiplexed instead of multiplexing the modulo time base expressed as prescribed in MPEG-4 at present; hence, it is possible to suppress the amount of information generated as compared with the method according to MPEG-4.

As described above, the image encoding device of Embodiment 9 which encodes images on the object-by-object basis is provided with time information encoding means which encodes, as information defining the display time of an image at each time on the object-by-object basis, first time information defining the time interval between the reference time and the display time and second information defining the display time with a higher accuracy than that of the time defined by the first time information and the image corresponding to each time; the time information encoding means expresses the first time information by conversion into a bit length, and when the bit length of the first time information is longer than a predetermined set value, a bit shift corresponding to the set value is repeated until the bit length becomes shorter than the set value, and at the same time, the number of bit shifts is counted, then the shift-repeat count and the bit string obtained by the repetitions of the bit shift are encoded.

EMBODIMENT 10

Embodiment 10 is directed to a VOP decoder which decodes the modulo time base information multiplexed onto the encoded bit stream in the modulo time base multiplexing part described above in Embodiment 9 and uses the decoded information and the VOP time increment to define the display time of each VOP.

Since Embodiment 10 differs from the VOP decoders described so far only in the configuration and operation of the header analysis part 151, a description will be given in this respect alone.

<figref idref="f0027">Fig. 29</figref> illustrates the internal configuration of the header analysis part 151 in Embodiment 10 of the present invention. Reference numeral 502 denotes a VOP header analysis part, 65 a modulo time base analysis part, 66 a VOP time increment analysis part, 67 a modulo time base calculation part, 69 a shifted modulo time base, and 70 an information bit indicating a shift-repeat count.

Next, the operation of this embodiment will be described. The start code analysis part 51 analyzes the start code contained in an encoded bit stream having multiplexed thereon the input shifted modulo time base 69 and the information bit 70 indicating the shift-repeat count, and outputs the bit stream 152 to the VO header analysis part 52 when the analyzed start code is contained in the VO header, to the VOL header analysis part 53 when the analyzed start code is contained in the VOL header, to the GOV header analysis part 54 when the analyzed start code is contained in the GOV header, to the VOP header analysis part 55 when the analyzed start code is contained in the VOP header, and to the video signal analysis part 153 (see <figref idref="f0009">Fig. 11</figref>) when the analyzed start code is contained in the VOP data information. The operations of the video signal analysis part and the parts following it are the same as described so far.

The modulo time base analysis part 65 in the VOP header analysis part 502 analyzes the shifted modulo time base 69 and the information bit 70 indicating the shift-repeat count contained in the bit stream fed from the start code analysis part 51, and outputs the shifted modulo time base 69 and the information bit 70 indicating the shift-repeat count to the modulo time base calculation part 67 and the bit stream to the VOP time increment analysis part 66.

The modulo time base calculation part 67 calculates the modulo time base from the shifted modulo time base 69 and the information bit 70 indicating the shift-repeat count, and outputs it to the composition part 210. More specifically, the value of the modulo time base is restored by reversing the procedure described previously with reference to Embodiment 9. In the case where a preset positive threshold value (The decoder side also required to set exactly the same value as the threshold value described in respect of the encoder of Embodiment 9.) and the shifted modulo time base 69 is "10" and the information bit 70 indicating the shift-repeat count is "10," "1111111110" with "11111111" added to the high-order bit of "10" is the restored value of the modulo time base. The thus obtained restored value of the modulo time base is used to define the display time of the VOP concerned, together with the VOP time increment information.

The VOP time increment analysis part 66 analyzes the VOP time increment contained in the bit stream fed from the modulo time base analysis part 65, and outputs the analyzed bit stream to the video information header analysis part 57. The video information header analysis part 57 analyzes the video information header contained in the bit stream fed from the VOP time increment analysis part 66, and outputs the analyzed bit stream to the video signal analysis part 153.

As described above, the decoder of Embodiment 10 is configured to calculate the modulo time base from the two kinds of information bits (the shifted modulo time base and the information indicating the shift-repeat count); hence it is possible to analyze the bit stream described later in Embodiment 12 which has a smaller amount of information generated than that by the encoded representation prescribed in MPEG-4.

As described above, the image display device of Embodiment 10 which decodes a bit stream with images encoded on the object-by-object basis is provided with: time information decoding means which decodes, as information defining the display time of an image at each time on the object-by-object basis, first time information defining the time interval between the reference time and the display time and second information defining the display time with a higher accuracy than that of the time defined by the first time information and the image corresponding to each time; and decoding and synthesizing means for decoding the input encoded image signal on the object-by-object basis and synthesizing these decoded image signals. The time information decoding means the time information encoding means expresses the first time information by conversion into a bit length, and when the bit length of the decodes, as encoded data of the first time information, a bit string derived from the bit-shift repeat count and the repeated bit shift and decodes the first time information by adding the bit string with code of a length of the predetermined set value by the bit-shift repeat count, and the decoding and synthesizing means synthesizes the decoded image signal on the basis of the first and second time information decoded by the time information decoding means.

EMBODIMENT 11

Embodiment 11 will be described in connection with another improved modulo time base encoding method and a VOP encoder therefore which are used to represent the modulo time base and the VOP time increment which are now used in MPEG-4.

Since Embodiment 11 differs from the VOP encoders described so far only in the configuration and operation of the header multiplexing part 124, a description will be given in this respect alone.

<figref idref="f0028">Fig. 30</figref> illustrates the internal configuration of the header multiplexing part 124 in Embodiment 11. Reference numeral 503 denotes a VOP header multiplexing part, 23 a modulo time base holding part, 24 a difference modulo time base generating part, 25 a difference modulo time base multiplexing part, and 26 a difference modulo time base.

The VOP start code multiplexing part 8 in the VOP header multiplexing part 503 multiplexes the VOP start code onto the input bit stream, and outputs the multiplexed bit stream to the difference modulo time base multiplexing part 25.

The modulo time base holding means 23 in the VOP header multiplexing part 503 holds the value of the modulo time base of the immediately previously encoded VOP, and after modulo time base of the immediately preceding encoded VOP is output therefrom, the modulo time base of the VOP to be encoded is written in the modulo time base holding part.

The difference modulo time base generating part 24 in the VOP header multiplexing part 503 calculates a bit string of the difference between the modulo time base of the immediately preceding encoded VOP input thereinto from the modulo time base holding part 23 and the modulo time base of the VOP to be decoded, then calculates the difference modulo time base 26 based on the number of bits "1" contained in the calculated difference bit string, and outputs it to the difference modulo time base multiplexing part 25.

Now, a concrete example of the generation of the difference modulo time base will be described.

In the case where the modulo time base of the immediately previously encoded VOP is "11110" (decimal numeral: 30) and the modulo time base of the VOP to be encoded is "111110" (decimal numeral: 62), the difference bit string becomes "100000" (decimal numeral: 32). Then, the number of bits "1" contained in the thus calculated difference bit string "100000" is one. In the case of calculating the difference modulo time base by such a conversion table as Table 2, the difference modulo time base corresponding to one bit "1" is "10," and consequently, "10" is output as the difference modulo time base. Table 2 is an example of the conversion table, and other conversion tables may also be defined.

Also it is possible to obtain the difference modulo time base simply by making a comparison of bit lengths alone. For example, in the above example the bit length of the modulo time base of the immediately previously encoded VOP is 5 and the bit length of the modulo time base of the VOP to be encoded is 6; therefore, a value of 1 is obtained as the difference. By using this value as a substitute for the "number of bits "1" contained in the difference bit string" in Table 2, the difference modulo time base can be expressed.

The difference modulo time base multiplexing part 25 in the VOP header multiplexing part 503 multiplexes the difference modulo time base 26 onto the input bit stream, and outputs the multiplexed bit stream to the VOP time increment multiplexing part 10.

The VOP time increment multiplexing part 10 in the VOP header multiplexing part 503 multiplexes the VOP time increment onto the bit stream fed from the difference modulo time base multiplexing part 25, and outputs the multiplexed bit stream to the video information header multiplexing part 11.

As described above, the encoder according to Embodiment 11 is adapted to express the modulo time base as the difference modulo time base and multiplex the difference modulo time base instead of encoding the modulo time base in the form presently prescribed in MPEG-4; hence, the amount of information generated can be made smaller than in the case of using the method prescribed in MPEG-4.

As described above, the image encoding device of Embodiment 11 which encodes images on the object-by-object basis is provided with time information encoding means which encodes, as information defining the display time of an image at each time on the object-by-object basis, first time information defining the time interval between the reference time and the display time and second information defining the display time with a higher accuracy than by the first time information and the image corresponding to each time; the time information encoding means has first time information holding means for holding the first time information encoded for the image at the immediately preceding time, and calculates a bit string of the difference between the first time information of the image to be encoded and the first time information of the image at the immediate preceding time provided from the first time information holding means, and encodes the difference bit string as the first time information of the image to be encoded.

EMBODIMENT 12

Embodiment 12 is directed to a VOP decoder which restores the value of the modulo time base of the VOP concerned from information about the difference modulo time base multiplexed onto the encoded bit stream in the difference modulo time base multiplexing part 25 described above in Embodiment 11 and uses the restored modulo time base value to define the display time of each VOP.

Since Embodiment 12 differs from the VOPs described so far only in the configuration and operation of the header analysis part 151, a description will be given in this respect alone.

<figref idref="f0029">Fig. 31</figref> illustrates the internal configuration of the header analysis part 151 in Embodiment 12 of the present invention. Reference numeral 504 denotes a VOP header analysis part, 71 a difference modulo time base analysis part, 72 a modulo time base generating part, 73 a VOP time increment analysis part, 74 a modulo time base holding part, and 75 a difference modulo time base.

The difference modulo time base analysis part 71 in the VOP header analysis part 504 analyzes the difference modulo time base 75 contained in a bit stream fed from the start code analysis part 51, and outputs the analyzed difference modulo time base 75 to the modulo time base generating part 72 and the analyzed bit stream to the VOP time increment analysis part 73.

The modulo time base generating part 72 in the VOP header analysis part 504 calculates the number of bits "1" contained in the bit string of the difference between the modulo time base of the immediately previously analyzed VOP and the modulo time base of the VOP to be analyzed, from the analyzed difference modulo time base 75 on the basis of the conversion table depicted as Table 3, then generates a modulo time base from the calculated number of bits "1" and the modulo time base of the immediately previously analyzed VOP available from the modulo time base holding part 74, and outputs the thus generated modulo time base to the modulo time base holding part 74.

A concrete example of the generation of the modulo time base will be described. Assume that the analyzed difference modulo time base is "10" and that the modulo time base analyzed immediately previously and held in the modulo time base holding part is "11110." In the case of calculating from the conversion table shown in Table 3 the number of bits "1" contained in the bit string of the difference between the modulo time base of the immediately previously analyzed VOP and the modulo time base of the VOP to be analyzed, it is known that the number of bits "1" contained in the difference bit stream corresponding to the difference modulo time base "10" is one. Then, one bit "1" is added to the most significant bit of the modulo time base "11110" of the immediately previously analyzed VOP to obtain a modulo time base. The conversion table of Table 2 is an example, and other conversion tables may also be defined and used. The restored value of the modulo time base is used to define the display time of the VOP concerned, together with the VOP time increment information.

Furthermore, the "number of bits "1" contained in the bit string of the difference between the modulo time base of the immediately previously analyzed VOP and the modulo time base of the VOP to be analyzed" may also be a bit stream encoded as the "difference value between the bit length of the modulo time base of the immediately previously analyzed VOP and the bit length of the modulo time base of the VOP to be analyzed," and in this case the interpretation of such a conversion table as Table 2 needs only to be changed.

The modulo time base holding part 74 in the VOP header analysis part 504 holds the modulo time base of the immediately previously analyzed VOP, and after modulo time base of the immediately preceding encoded VOP is output therefrom, the modulo time base of the VOP to be encoded is input into the modulo time base holding part.

The VOP time increment analysis part 73 in the VOP header analysis part 504 analyzed the VOP time increment contained in the bit stream fed from the difference modulo time base analysis part 71, and outputs the analyzed bit stream to the video information header analysis part 57.

As described above, the decoder of Embodiment 12 is adapted to calculate the modulo time base from the difference time modulo base with a small amount of information; hence it is possible to analyze the bit stream described previously in Embodiment 8 which has a smaller amount of information generated than that by the encoded representation prescribed in MPEG-4.

As described above, the image decoding device of Embodiment 12 which decodes a bit stream with images encoded on the object-by-object basis is provided with: time information decoding means which decodes first time information defining the time interval between the reference time and the display time and second information defining the display time with a higher accuracy than that of the time defined by the first time information, as information defining the display time of an image at each time in an image series, and the image corresponding to each time; and decoding and synthesizing means for decoding the input encoded image signal on the object-by-object basis and synthesizing these decoded image signals. The time information decoding means holds the first time information of the immediately previously decoded image, then adds the first time information of the immediately decoded image available from the first time information holding means to a bit string decoded as the first time information of the image to be decoded, thereby decoding the first time information of the image to be decoded; and the decoding and synthesizing means synthesizes the decoded image signal on the basis of the first and second time information decoded by the time information decoding means.

EMBODIMENT 13

While in Embodiments 1 through 12 there have been described above that the image encoding device multiplexes the display speed information onto the encoded image signal and that the image encoding device multiplexes the absolute time information onto the encoded image signal, it is also possible to implement an image encoding device which multiplexes both the display speed information and the absolute time information onto the encoded image signal.

This can be done by a parallel or series arrangement of display speed information multiplexing means and absolute time information multiplexing means in the respective image encoding device described in each of Embodiments 1 to 12.

The same goes for the image decoding device side. To put it simply, there have been described above in Embodiments 1 through 12 that the image decoding device decodes the display speed information and uses this decoded display speed information to reconstruct images processed on the object-by-object basis and that the image decoding device decodes the absolute time information and uses the decoded absolute time information to reconstruct images processed on the object-by-object basis; however, it is also possible to implement an image decoding device which reconstructs the images processed for each object on the basis of the display speed information and the absolute time information.

This can be done by a parallel or series arrangement of the display speed information decoding part and the absolute time information decoding part in the respective image decoding device described in each of Embodiments 1 to 12 so that images processed for each object are reconstructed based on the information decoded in each decoding part.

With the above configuration, the image restoration and synthesis can be performed more smoothly and more accurately.

EMBODIMENT 14

While in Embodiments 1 through 13 there have been described above that the image encoding device encodes and multiplexes the display speed information on the encoded image signal and that the image encoding device multiplexes the first time information, the second time information and the image, it is also possible to implement an image encoding device which encodes and multiplexes the display speed information, the first time information, the second time information and the image.

This can be done by a parallel or series arrangement of the display speed information multiplexing means and the first and second time information and image multiplexing means in the respective image encoding device described in each of Embodiments 1 to 13.

The same goes for the image decoding device side. To put it briefly, there have been described above in Embodiments 1 through 13 that the image decoding device decodes the display speed information and, based on the decoded display speed information, reconstructs images processed for each object and that the image decoding device decodes the first time information, the second time information and the image and, based on the decoded first time information, second time information and image, reconstructs the image; however, it is also possible to implement an image decoding device reconstructs images on the basis of the display speed information and the decoded first and second time information.

This can be done by a parallel or series arrangement of the display speed information decoding part and the time information decoding part in the respective image decoding device described in each of Embodiments 1 to 13 so that images processed for each object are reconstructed based on the information decoded in each decoding part (means).

With the above configuration, the image restoration can be performed more smoothly and more accurately with a small amount of coded information sent.

EMBODIMENT 15

While in Embodiments 1 through 14 there have been described above that the image encoding device multiplexes the absolute time information and encoded image signal and that the image encoding device encodes and multiplexes the first time information, the second time information and the image, it is also possible implement an image encoding device which encodes and multiplexes the absolute time information, the first and second time information and the image.

This also can be achieved by a parallel or series arrangement of the absolute time multiplexing means and the first and second time information and image encoding and multiplexing means in the respective image encoding device described in each of Embodiments 1 to 14.

The same goes for the image decoding device side. To put it simply, there have been described above in Embodiments 1 through 14 that the image decoding devices decode the absolute time information and, based on the decoded absolute time information, reconstruct images processed for each object and that the image decoding devices decode the first time information, the second time information and the image and reconstruct the image, based on the decoded first time information, second time information and image; however, it is also possible to implement an image decoding device reconstructs images on the basis of the absolute time information and the decoded first and second time information.

This can also be achieved by a parallel or series arrangement of the absolute time information decoding part and the time information decoding part in the respective image decoding device described in each of Embodiments 1 to 13 so that images processed for each object are reconstructed based on the information decoded in each decoding part (means).

With the above configuration, the image restoration can be achieved more smoothly and more accurately with a small amount of coded information sent.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, the image decoding device analyzes the display speed information multiplexed in the image encoding device and performs decoding based on the analyzed display speed information, thereby permitting smooth image reconstruction with a simple structure. Furthermore, the image decoding device decodes the absolute time information multiplexed in the image encoding device and performs decoding based on the analyzed absolute time information, thereby permitting the image reconstruction with ease and with high accuracy. Moreover, the image decoding device decodes the first and second time information encoded in the image encoding device and decodes the input image signal based on the decoded first and second time information, thereby permitting the reception of the image signal with a small amount of information sent. <tables id="tabl0001" num="0001"><table frame="all"><title><b>TABLE 1</b></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="26mm" /><colspec colnum="2" colname="col2" colwidth="44mm" /><thead><row><entry align="center" valign="top">VOP RATE</entry><entry align="center" valign="top">VOP RATE INFORMATION</entry></row></thead><tbody><row><entry align="center">30/SEC</entry><entry align="center">01</entry></row><row><entry align="center">15/SEC</entry><entry align="center">10</entry></row><row><entry align="center">STILL PICTRE</entry><entry align="center">00</entry></row><row><entry align="center">VARIABLE</entry><entry align="center">11</entry></row></tbody></tgroup></table></tables><tables id="tabl0002" num="0002"><img file="EP1909501A2_D0001.tif" /></tables><tables id="tabl0003" num="0003"><table frame="all"><title><b>TABLE 3</b></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="118mm" /><colspec colnum="2" colname="col2" colwidth="44mm" /><thead><row><entry align="center" valign="top">VOP RATE</entry><entry align="center" valign="top">VOP RATE INFORMATION</entry></row></thead><tbody><row><entry align="center">2/SEC</entry><entry align="center">000</entry></row><row><entry align="center">5/SEC</entry><entry align="center">001</entry></row><row><entry align="center">25SEC</entry><entry align="center">010</entry></row><row><entry align="center">30/SEC</entry><entry align="center">011</entry></row><row><entry align="center">FIXED FOP RATES OTHER THAN THE ABOVE (2/SEC, 5/SEC, 25/SEC, 30/SEC)</entry><entry align="center">100</entry></row></tbody></tgroup></table></tables><tables id="tabl0004" num="0004"><table frame="all"><title><b>TABLE 4</b></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="118mm" /><colspec colnum="2" colname="col2" colwidth="44mm" /><thead><row><entry align="center" valign="top">VOP RATE</entry><entry align="center" valign="top">VOP RATE INFORMATION</entry></row></thead><tbody><row><entry align="center">2/SEC</entry><entry align="center">000</entry></row><row><entry align="center">5/SEC</entry><entry align="center">001</entry></row><row><entry align="center">25SEC</entry><entry align="center">010</entry></row><row><entry align="center">30/SEC</entry><entry align="center">011</entry></row><row><entry align="center">FIXED FOP RATES OTHER THAN THE ABOVE (2/SEC, 5/SEC, 25/SEC, 30/SEC)</entry><entry align="center">100</entry></row><row><entry align="center">STILL PICTURE</entry><entry align="center">101</entry></row></tbody></tgroup></table></tables>