Optical disk device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an optical disk device for reproducing digitally compressed image data, and more particularly to an optical disk device capable of performing high-speed reproduction of about 2x speed and 3x speed.

【0002】

[Conventional technology]

In recent years, in order to efficiently store an image on an optical disk such as a CD-ROM, the image data to be stored is subjected to intra-coding, which is coding within a field or frame, and inter-field or frame-to-frame coding. It has been proposed to compress and then accumulate by some forward coding and bidirectional predictive coding. Intra-coding is a coding method that uses information only in one image. When the intra-encoded image data is decoded, one image can be reconstructed only by the data. Further, forward predictive coding and bidirectional predictive coding are methods for encoding differences from images located forward or backward in time, and decode only forward predictive coding or bidirectional predictive coding data. However, one image cannot be reconstructed, but the amount of image data to be encoded can be significantly reduced.

【0003】

Conventionally, high-speed image reproduction such as cueing (fast-forwarding) and review (fast-forwarding in the reverse direction) is performed by rotating the optical disc at the same speed as the normal rotation speed and reading only the intra-encoded data from the optical disc. Was there. This is because the intra-encoded image data can reconstruct one image from itself.

【0004】

[Problems to be Solved by the Invention]

However, usually, the intra-encoded image data is contained only at a ratio of one in a dozen or so frames. Therefore, in the conventional high-speed reproduction in which only the intra-encoded image data is reproduced, it is inevitable that the temporal resolution is significantly deteriorated.

【0005】

In particular, in order to perform reproduction at about 2x speed and 3x speed using only the intra-encoded image data, the image obtained from the image data corresponding to one image is subjected to the next intra-encoding. The image data must be repeatedly reproduced multiple times until it is decoded and reproduced. Therefore, it is impossible to display a smooth reproduced image at 2x or 3x speed by using only the intra-encoded image data as in the conventional case.

【0006】

In addition, normally, the time required to read the intra-encoded one field or one frame of image data from the optical disk and decode it is the time required for the decoded one field or one frame of image data to be displayed in the image display unit. It takes longer than the time to output to and play back (1 frame = 1/30 sec). Therefore, the data of the image to be displayed next cannot be decoded within the time during which one decoded image is being reproduced. Therefore, one image that has already been reproduced must be repeatedly reproduced until the data of the image to be displayed next is decoded. As described above, the conventional high-speed reproduction technology has a problem that the images cannot be reproduced one by one continuously.

【0007】

Further, usually, not only in high-speed reproduction but also in variable speed reproduction, the sound is muted. This is because even if the audio data is decoded, the obtained audio cannot be reproduced together with the image.

【0008】

The present invention has been made in view of such a current situation, and an object of the present invention is to display a smooth image in reproduction at a speed slightly faster than a normal reproduction speed such as 2x speed or 3x speed, and further, an image. It is an object of the present invention to provide an optical disk device capable of reproducing audio together with the above.

【0009】

[Means for solving problems]

The optical disk device of the present invention is a signal processing means for reading image data and audio data from an optical disk and generating an image data signal and an audio data signal according to the read image data and the audio data, and the signal processing means. It is provided with an image decoder means for receiving the image data signal from the user and generating a reproduced image signal based on the received image data signal, and a control means for generating a high-speed reproduction control signal for switching from normal reproduction to high-speed reproduction. The image decoder means is one of the image data decoding means for decoding the image data signal and the decoded image data signal when the high-speed reproduction control signal is received from the control means. Only the signal corresponding to the intra-encoded image data and the forward predictive encoded image data is generated as the reproduced image signal, and at other times, the decoded image data signal is generated as the reproduced image signal. It has means, thereby achieving the above objectives.

【0010】

The optical disk device further includes an audio decoder means that generates a reproduced audio signal based on the audio data signal from the signal processing means, and the audio decoder means receives the high-speed reproduction control signal from the control means. At that time, only the portion of the audio data signal generated in the first period is demodulated, and the portion generated in the second period following the first period is demodulated without being demodulated. Only the portion generated in the first period is output as the reproduced audio signal, and at other times, all the audio data signals are decoded and output as the reproduced audio signal, and the first period and the second period are output. Periods may be repeated alternately.

【0011】

In the optical disk device, the first period may correspond to nGOP (n 1), and the second period may correspond to mGOP (m 1).

【0012】

The optical disk device further includes a motor for rotating the optical disk and a motor driving means for driving the motor, and the motor driving means receives the high-speed reproduction control signal from the control means. By increasing the rotation speed of the motor in response to the high-speed reproduction control signal to a rotation speed higher than the minimum required for normal reproduction, the speed at which the image data and the audio data are read from the optical disk may be increased. ..

【0013】

The optical disk device further includes a voice decoder means that receives the voice data signal from the signal processing means and generates a reproduced voice signal based on the received voice data signal, and the voice decoder means includes the voice. When the means for demolishing the data signal and the high-speed reproduction control signal are received from the control means, the demolished audio data signal is temporally compressed and output as the reproduced audio signal, and is demolished at other times. It may also have a means for outputting the reproduced audio signal without compressing the audio data signal.

【0014】

[Action]

According to the present invention, all image data recorded on an optical disc is read out regardless of the speed at which the image is reproduced. At the time of normal reproduction, all of the read image data is decoded and output as a reproduced image signal, but at the time of high-speed reproduction, the intra-encoded image data of the read image data and the forward prediction Only the encoded image data is output as a reproduced image signal. As a result, only the intra-encoded image data is read from the optical disc, decoded, and output, so that the time resolution is improved and smoother than that of the conventional optical disc device that reproduces the image at high speed. Image reproduction can be performed.

【0015】

In addition, during high-speed playback, all image data can be read even during high-speed playback by changing the rotation speed of the motor to a speed higher than the minimum required to achieve the transfer rate during normal playback. Is possible.

【0016】

Further, according to the present invention, the audio data signal generated in the first period is demodulated, and the audio data signal output in the subsequent second period is omitted without being demodulated and generated in the first period. Since the audio data signal is output as a reproduced audio signal until the start of the next first period, the audio is reproduced almost in synchronization with the image.

【0017】

[Example]

First, the principle of the coding method of the image data recorded on the optical disk will be described.

【0018】

Figure 1 shows the frame sequence by the image coding method proposed by MPEG. One frame corresponds to one screen (picture) and is encoded in picture units. There are three types of pictures: I picture, P picture, and B picture. The I picture is a picture obtained by intra-frame coding (intra-coding). For in-frame coding, closed information is used only in one image. In-frame coding is generally inefficient. The P picture is a picture obtained by encoding an I picture or a P picture located in front of the time using a reference for taking a difference. As the B picture, an interpolated image created from an I picture or P picture located in front of the time, an I picture or P picture located in the rear of time, or both of them is used.

【0019】

In the frame sequence shown in FIG. 1, the 1st and 13th frames are I pictures, the 4th, 7th and 10th frames are P pictures, and the 2nd, 3rd, 5th, 6th, 8th, 9th, 11th and 12th frames are B pictures. It is shown that. The frame sequence from the 1st frame to the 12th frame constitutes 1GOP (Group of Picture).

【0020】

Subsequently, the optical disk device according to the present invention will be described with reference to FIG. The optical disc 1 on which the intra-coded, forward-predictive-coded, and bidirectional predictive-coded digital image data is recorded is rotated by the motor 10. The motor 10 is driven by the motor drive circuit 9. The data recorded on the optical disk 1 is optically read by the reproduction head 2 and input to the reproduction signal processing unit 3 as an electric signal. The reproduction signal processing unit 3 has a signal processing circuit 4 and a decoder circuit 5, and after performing processing such as digital demodulation and error correction on the electric signal input from the reproduction head 2, the output terminal 11 is used. The reproduced image signal is output to the output terminal 12, and the reproduced audio signal is output to the output terminal 12.

【0021】

A high-speed reproduction control circuit 8 is connected to the decoder circuit 5 and the motor drive circuit 9. The terminal 13 is connected to the high-speed reproduction control circuit 8. When the high-speed reproduction control circuit 8 receives a signal commanding high-speed reproduction from the terminal 13, the high-speed reproduction control circuit 8 controls the motor drive circuit 9 to increase the rotation speed of the optical disc to be higher than the rotation speed required for normal reproduction, and at the same time, in the decoder circuit 5. The image decoder circuit 6 and the audio decoder circuit 7 of the above are controlled to perform a predetermined operation.

【0022】

FIG. 3 is a block diagram showing the configuration of the image decoder circuit 6. The image data signal output from the signal processing circuit 4 is input from the terminal 61 in the order of the inverse quantizer 62 and the inverse discrete cosine transform circuit (hereinafter, simply referred to as the inverse DCT circuit) 63. The dequantized and inverse discrete cosine transformed image data signals are input to the adder 64. The signal output from the adder 64 is input to the predictor 65. The image signal output from the predictor 65 is input to the adder 64 again via the switch 66. The switch 66 is open only when the image signal output from the predictor 65 corresponds to the I picture, and is always closed at other times. The opening and closing of the switch 66 is controlled by the controller 69. The image signal output from the adder 64 in this way is input to the switch 67. During normal playback, the switch 67 is always closed, and all the image signals input to the switch 67 are sent to the output buffer 68. The output of the output buffer 68 is connected to the terminal 11, and the reproduced image signals corresponding to the I picture, the P picture, and the B picture are output frame by frame from the terminal 11. During high-speed playback, the switch 67 is closed when the input image signal corresponds to the I picture and the P picture, and opens when the input image signal corresponds to the B picture. Therefore, at the time of high-speed playback, only the image signals corresponding to the I picture and the P picture are input to the output buffer 68. In this embodiment, the opening and closing of the switch 67 is controlled by the controller 69 as in the switch 66.

【0023】

FIG. 4 shows a first configuration example of the audio decoder circuit 7. The audio data signal output from the signal processing circuit 4 is input from the terminal 71 to the switch 72. When the switch 72 receives the control signal from the controller 75, the switch 72 closes and conducts for a predetermined period of time. When the switch 72 is closed, the audio data signal is input to the input buffer 73. The input buffer 73 outputs the input audio data signal to the DEM 74. When it is detected by a detection circuit (not shown) that the amount of data of the audio data signal stored in the input buffer 73 is less than a predetermined amount, the controller 75 controls the switch 72 based on the detection result of the detection circuit. Generates a control signal. As a result, the voice data signal input to the switch 72 when the switch 72 is closed is input to the input buffer 73. The audio data signal input to the DEM74 is digitally demodulated and output to the terminal 12.

【0024】

Hereinafter, the operation of the optical disc device during normal playback and high-speed playback will be described with reference to FIGS. 3, 4, and 5.

【0025】

FIG. 5 (a) shows the coding pattern of the signal recorded on the optical disk 1. As explained with reference to FIG. 1, the image data of the 1st, 13th, 25th, and 37th frames are intra-coded, and the image data of the 4th, 7th, 10th, 16th frames, etc. are forward. Predictive coding is performed, and image data such as the second, third, fifth, and sixth frames are predictively coded in both directions and recorded on the optical disk 1. In the case of normal reproduction, the motor drive circuit 9 controls the motor 10 so that the optical disc 1 rotates at a predetermined speed. Information including audio data and image data is optically read from the rotating optical disk 1 by the playback head 2 and output as an electric signal. FIG. 5B shows a data string read by the playback head 2 during normal playback. The horizontal axis represents the time axis. The output time of one frame is 1/30 sec regardless of the coding method, but the amount of data per frame differs depending on the coding method. The amount of data in the intra-coded frame is the largest, and the amount of data in the bidirectional predictive coded frame is the smallest. Therefore, as can be seen from FIG. 5 (b), the time required to read the image data of the intra-coded frame is longer than the time required to read the image data of the frame predicted forward-coded or bidirectionally predicted. It takes a long time. Further, immediately before the image data of the intra-encoded frame, the audio data corresponding to the GOP to which the frame belongs is recorded.

【0026】

The signal output from the playback head 2 is input to the image decoder circuit 6 and the audio decoder circuit 7 via the signal processing circuit 4. The image decoder circuit 6 decodes the image data as described above and outputs the image data to the image terminal 11 of one frame in the order of recording on the optical disk 1. FIG. 5 (c) shows a pattern of the reproduced image signal that is decoded and output from the image decoder circuit 6 to the terminal 11. In this optical disk device, the time for reading 1 GOP of data from the optical disk 1 during normal playback is set to be equal to the time for outputting the reproduced image signal for 1 GOP to the terminal 11. The time for reading the data for 1 GOP may be slightly shorter than the time for outputting the reproduced image signal for 1 GOP to the terminal 11. The reproduced image signal output to the terminal 11 is supplied from the terminal 11 to an image display unit (not shown). When the image display unit receives the reproduced image signal via the terminal 11, the image display unit displays an image of one frame for 1/30 sec each.

【0027】

Further, the audio data is recorded immediately before the image data of the corresponding GOP of the audio data as shown in FIG. 5 (b). The audio data read by the playback head 2 is subjected to predetermined processing by the signal processing circuit 4 and input to the audio decoder circuit 7. In the voice decoder circuit 7, the input voice data signal is decoded as described above and output to the terminal 12.

【0028】

More specifically, first, the voice data A1 corresponding to the first 1 GOP is input to the input buffer 73. The audio data signal A1 input to the input buffer 73 is output to the DEM 74. When the remaining amount of the voice data signal A1 stored in the input buffer 73 becomes low, the controller 75 generates a control signal to close the switch 72. The audio data signal first input from the terminal 71 after the switch 72 is closed is input to the input buffer 73 as the next audio data signal of the audio data signal A1. The speed at which the audio data signal is output from the input buffer 73 to the DEM 74 is set so that the audio data signal first input after the switch 72 is closed during normal playback is A2. In this way, at the time of normal reproduction, the reproduced audio signal is output from the terminal 12 in synchronization with the reproduced image signal of the corresponding GOP.

【0029】

Next, the operation of the optical disk device 1 of the present invention in the case of performing reproduction at 3x speed will be described. The optical disk device of the present invention uses only I-pictures and P-pictures when reproducing images at 3x speed, but when reading image data from optical disk 1, only I-pictures and P-pictures are selectively read out. Have difficulty. This is because the B picture and the P picture are recorded in a mixed manner as shown in FIG. 5 (b). Further, even if the I picture and the P picture can be selectively read out, this may complicate the device. Therefore, the optical disk device of the present invention adopts a method of reading all the data from the optical disk 1 and omitting the image data corresponding to the B picture from the read image data, and in order to realize this, high speed is adopted. During playback, the transfer rate is set higher than the transfer rate during normal playback.

【0030】

First, a high-speed reproduction signal is input from the terminal 13 from a CPU or the like (not shown). For example, the high-speed reproduction signal includes a signal indicating the speed at which an image is reproduced, such as 3x speed and 2x speed. The high-speed reproduction control circuit 8 controls the motor drive circuit 9 based on the received high-speed reproduction signal to increase the rotation speed of the optical disc 1. Assuming that the image is reproduced at n times the rotation speed of the optical disc 1 at the time of high-speed reproduction, the rotation speed is set to n times the minimum rotation speed required to realize the transfer rate at the time of normal reproduction. For example, if the transfer rate during normal playback is 3.0 Mbps and the rotation speed during normal playback of optical disc 1 is set to the minimum rotation speed that can achieve this transfer rate, image playback at 3x speed is performed. Occasionally, the rotation speed of optical disc 1 is tripled. When the rotation speed is tripled, the transfer rate becomes 9.0 Mbps, and as shown in Fig. 5 (d), the time required to read 1 GOP of data from optical disk 1 is reduced to one-third. In this way, the transfer rate is increased to three times that during normal playback, and all image data is read out.

【0031】

Upon receiving the high-speed reproduction signal, the high-speed reproduction control circuit 8 outputs the high-speed reproduction control signal to the image decoder circuit 6. The controller 69 of the image decoder circuit 6 receives the signal from the high-speed playback control circuit 8. The operation of the image decoder circuit 6 will be described below. As for the image data signal output from the signal processing circuit 4, the image data signal from the terminal 61 is inversely quantized and inverse discrete cosine transformed as described above, and is output as an image signal from the adder 64 as described above. Entered in 67. The switch 67 is controlled by the controller 69 to be closed when the image signal corresponds to the I picture and the P picture and to open when the image signal corresponds to the B picture, so that the output buffer 68 has the I picture and the P picture. Only the image signal corresponding to is input. The image signal input to the output buffer 68 is output once per frame. Therefore, a signal for displaying one image once is output to the terminal 11 as a reproduced image signal.

【0032】

FIG. 5 (e) shows the pattern of the reproduced image signal output from the image decoder circuit 6 to the terminal 11. As described above, when the image decoder circuit 6 of the optical disk device omits the image data signal corresponding to the B picture and reproduces only the reproduced image signal corresponding to the I picture and the P picture at a normal speed. Similarly, 1/30 sec per frame is output to terminal 11. Therefore, unlike the conventional optical disk device that outputs only the reproduced image signal corresponding to the I picture, the image reproduction at 3x speed can be realized by outputting the image of one frame only once per GOP. Further, since not only the I picture but also the P picture is used, the temporal resolution can be improved as compared with the conventional optical disk device, and a smoother image can be reproduced.

【0033】

The operation of the audio decoder circuit 7 when reproducing an image at 3x speed is almost the same as the operation when reproducing an image at a normal speed. First, the voice data corresponding to the first 1 GOP is input to the input buffer 73. The input audio data signal A1 is output from the input buffer 73 to the DEM 74. As described above, the speed at which the audio data signal A1 is output corresponds to the audio data signal stored in the input buffer 73 during normal playback when the audio data signal first input after the switch 72 is closed. It is set to correspond to 1GOP following 1GOP. When the remaining amount of the audio data signal A1 stored in the input buffer 73 falls below a predetermined amount, a detection circuit (not shown) detects this and outputs the detection signal to the controller 75. Upon receiving the detection signal, the controller 75 generates a control signal to close the switch 72. Subsequently, the voice data signal first input from the terminal 71 after the switch 72 is closed is input to the input buffer 73. Here, as shown in FIG. 5D, when the image is reproduced at 3x speed, the data for 1 GOP is read out in one-third of the time during normal reproduction, so that the input buffer 73 is used. While the audio data signal A1 is being output to the DEM74, the audio data signals A2 and A3 are read from the optical disk 1 and input from the terminal 71 to the switch 72. Therefore, the voice data signal A4 is input to the input buffer 73 after the voice data signal A1. Similarly, the voice data signal A7 is input to the input buffer 73 next to the voice data signal A4.

【0034】

The audio data signal input to the input buffer 73 in this way is output from the DEM 74 to the terminal 12. At this time, each of the audio data signals is output for the same time as the time required to output the image for 1 GOP to the terminal 11 during the normal playback as in the normal playback. FIG. 5 (e) shows the pattern of the reproduced audio signal output to the terminal 12 together with the pattern of the reproduced image signal output to the terminal 11 when the image is reproduced at 3x speed. As can be seen from this figure, this optical disk device synchronizes the reproduced audio signal with the reproduced image signal at the same speed as when the image is reproduced at a normal speed, although it is discrete, and when viewed in 3 GOP units. It can be output to terminal 12.

【0035】

In this way, the optical disc device can reproduce a smooth image with sound at 3x speed. In this optical disk device, audio is reproduced discretely such as A1, A4, and A7, but if it is reproduced at this level, the content can be sufficiently grasped.

【0036】

Next, the operation of the optical disk device when performing playback at double speed will be described. In this case as well, the motor drive circuit 9 uses the high-speed reproduction control circuit 8 to set the rotation speed of the optical disk to the minimum rotation required to reproduce the image at the normal speed, as in the case of image reproduction at 3x speed. It is controlled to be set to twice the speed.

【0037】

The operation of the image decoder circuit 6 is also almost the same as when the image is reproduced at 3x speed, but the method of outputting the reproduced image signal from the output buffer 68 to the terminal 11 is different from the image reproduction at 3x speed. The image data signal from the signal processing circuit 4 input from the terminal 61 is inversely quantized and inverse discrete cosine transformed as described above, and is input to the switch 67. The image signal input to the switch 67 includes all the image signals corresponding to the I picture, the P picture, and the B picture. The image signal input to the switch 67 is sent to the output buffer 68 after only the image signal corresponding to the B picture is omitted by opening and closing the switch 67.

【0038】

The image signals corresponding to the I picture and P picture stored in the output buffer 68 are output to the terminal 11 once per frame when the image is played back at 3x speed, but the image is played back at 2x speed. In some cases, some frames are output multiple times, and other frames are output once. In this optical disk device, as shown in FIG. 5 (f), image signals of the first, seventh, thirteenth, nineteenth, 25th, and 31st frames are output twice, and images of other frames are output. The signal is output once. In this way, when the image is reproduced at double speed, the image signal corresponding to the I picture and the image signal corresponding to the middle P picture of each GOP P picture are transmitted twice to the I picture. The image signal corresponding to the P picture immediately before and immediately after is output to the terminal 11 once, and is supplied to the image display unit as a reproduced image signal from the terminal 11.

【0039】

In this way, even in this optical disk device, the image signal of some frames is output a plurality of times as in the case of performing image reproduction at double speed in the conventional device, but in this optical disk device, I Since not only a picture but also a P picture is used, the temporal resolution can be dramatically improved as compared with the conventional case.

【0040】

Further, the operation of the audio decoder circuit 7 when reproducing an image at 2x speed is the same as when reproducing an image at a normal speed and when reproducing an image at 3x speed. In this case, the pattern of the reproduced audio signal output to the terminal 12 is shown in FIG. 5 (f). Following the voice data signal A1, the voice data signal A3 is input to the input buffer 73, and then the voice data signals A5 and A7 are input in this order. The input audio data signal is subjected to predetermined processing by the DEM 74 and output as a reproduced audio signal from the terminal 12. Therefore, when the image is reproduced at double speed, the reproduced audio signal is output from the terminal 12 in approximately synchronization with the reproduced image signal output from the terminal 11 in units of 2 GOP. In this way, the optical disc device can reproduce audio that is discrete but substantially synchronized with the image.

【0041】

As described above, this optical disk device can reproduce an image at double speed with sound that is smoother than before and that is almost synchronized with the image. The audio will be reproduced discretely, such as A1, A3, A5, and A7, but if it is reproduced to this extent, the content can be fully grasped.

【0042】

This optical disk device reproduces sound at a normal speed even when the image is reproduced at 2x or 3x speed. However, in order to obtain more complete voice information, it is also possible to decode all voice data signals and compress the decoded voice signals in time. For example, as a method of compressing an audio signal by half in time, there is a method of doubling the output clock of the audio. However, with this method, the voice pitch (frequency) is increased by an octave. Recently, a method of temporally compressing a voice signal without changing the voice pitch has also been proposed. By using this method, as shown in FIG. 5 (g), all sounds can be reproduced.

【0043】

FIG. 6 briefly shows the configuration of the voice decoder circuit 107 when the voice signal is timely compressed without changing the voice pitch. The audio data signal from the signal processing circuit 4 is input from the terminal 171. When playing back an image at normal speed, switch 172 is closed, switch 177 is open, and all audio data signals input from terminal 171 are input to input buffer 173 and then to DEM174. The audio signal output from DEM174 is input to switch 175. During normal playback, the switch 175 is in a state shown by a solid line in the figure, and the audio signal input to the switch 175 is directly input to the terminal 12. Here, it is assumed that the switches 172, 175 and 177 are controlled by a controller (not shown).

【0044】

When the image is reproduced at double speed, only one of the switch 172 and the switch 177 is controlled to open and close alternately. For example, when the first audio data signal A1 is input from terminal 171, switch 172 is closed, switch 177 is open, and audio data signal A1 is input to input buffer 173 via switch 172. When the next voice data signal A2 is input, the switch 172 is opened and the switch 177 is closed, and the voice data signal A2 is input to the input buffer 178. In this way, the odd-numbered audio data signal is input to the input buffer 173, and the even-numbered audio data signal is input to the input buffer 178. The audio data signal input to the input buffer 173 is processed by the DEM 174 and then output to the switch 175. The switch 175 is in a state as shown by a broken line in the figure when the image is reproduced at double speed. Therefore, the audio signal from the DEM 174 is halved by the audio compression circuit 176 and then input to the multiplexer 181. The even-numbered audio data signal also passes through the input buffer 178 and DEM179, is halved by the audio compression circuit 180, and then input to the multiplexer 181. The multiplexer 181 synthesizes the odd-numbered audio signal and the even-numbered audio signal, and outputs the reproduced audio signal from the terminal 12.

【0045】

In this way, the audio signal can be compressed in half in time and reproduced in its entirety without changing the audio pitch. In addition to the methods described above, all audio data can be reproduced by using a known audio compression technique.

【0046】

Further, in the above embodiment, when the image is reproduced at a normal speed, the optical disk 1 is rotated at the minimum rotation speed required to realize the transfer rate in this case, but the rotation speed is higher than that. Optical disc 1 may be rotated at a speed. In such a case, when a predetermined amount of data sent from the reproduction head 2 to the reproduction signal processing unit 3 is stored in the buffer, so-called intermittent reproduction is performed in which the data is still and waits. Further, if the rotation speed of the optical disk 1 when the image is reproduced at a normal speed is the minimum rotation speed required to realize the transfer rate required when the image is reproduced at a double speed, the rotation speed is the minimum. It is not necessary to increase the rotation speed of the optical disk 1 when playing back a double-speed image. Further, if the optical disk 1 is rotating at the minimum rotation speed required for image reproduction at 3x speed during normal reproduction, it is not necessary to increase the rotation speed when reproducing the image at 2x or 3x speed. In this case, the above-mentioned intermittent reproduction is performed when the image is reproduced at double speed.

【0047】

The increase in the rotation speed, that is, the increase in the transfer rate is not limited to twice or three times as described in the above embodiment. Even if the transfer rate is increased by about 10 times, the same effect as that described in the above embodiment can be obtained. In this case, the frequency of the clock used for processing the reproduced signal also needs to be increased as the transfer rate increases. Also, during normal playback, if the optical disk 1 is rotating at a rotation speed that can achieve a transfer rate higher than the transfer rate during image playback at 2x or 3x speed, then high-speed playback is performed. There is no need to increase the rotation speed.

【0048】

In the above embodiment, an example in which the image of the same frame is displayed once or twice during high-speed playback has been described, but the number of times the image of the same frame is displayed is not limited to once or twice, for example, from once. It may be switched between three times depending on the speed at which the image is played back.

【0049】

Further, in the above embodiment, the case of reproducing the in-frame or inter-frame encoded image data has been described, but the present invention is also applied to the case of reproducing the in-field or inter-field encoded image data. Of course you can.

【0050】

In the above embodiment, the opening and closing of the switches of the image decoder circuit and the audio decoder circuit is controlled by the controller. However, the opening and closing of the switch may be controlled by any method, and if it is controlled to be closed for the I picture and the P picture and open for the B picture, the above-mentioned effect can be obtained. A similar effect can be obtained.

【0051】

Further, in the above embodiment, the audio data is reproduced in units of 1 GOP, but the unit for reproducing the audio data is not limited to 1 GOP, and may be, for example, in units of 1 second or several seconds. In this case, the sound and the image do not need to be reproduced in perfect synchronization, and as described in the above embodiment, for example, the sound and the image may be synchronized when viewed in units of several GOPs or units of seconds. ..

【0052】

[Effect of the invention]

According to the present invention, since the transfer rate is made higher than the normal transfer rate at the time of high-speed reproduction, it is possible to omit the image data signal corresponding to the B picture after reading all the data. As a result, only the I picture and the P picture can be reproduced, and the temporal resolution can be significantly improved as compared with the conventional device that reproduces only the I picture. Therefore, it becomes possible to reproduce a smoother image at a higher speed than before.

【0053】

Further, according to the present invention, although it is discrete, the sound can be reproduced in substantially synchronization with the image, so that high-speed image reproduction with sound can be realized.

[Simple explanation of drawings]

[Figure 1]

Explanation of the principle of the coding method of image data recorded on an optical disk [Figure 2]

Configuration diagram of the optical disk device of the present invention [Fig. 3]

Configuration diagram of the image decoder circuit of the present invention [Fig. 4]

Configuration diagram of the audio decoder circuit of the present invention [Fig. 5]

Schematic diagram of the reproduction signal pattern in the embodiment of the present invention [Fig. 6]

Another block diagram of the audio decoder circuit of the present invention [Explanation of symbols]

1 optical disc 2 Playback head 3 Playback signal processing unit 4 Signal processing circuit 5 Decoder circuit 6 Image decoder circuit 7 Audio decoder circuit 8 High-speed playback control circuit 9 Motor drive circuit 10 motor