Method and arrangement for encoding and decoding a sequence of digital data

Translation of description of equivalent WO 03107581 A2

description

Method and apparatus for encoding or decoding a sequence of digital data.

The invention relates to a method and an arrangement for encoding and a method and an arrangement for decoding a sequence of digital data.

From [1] is a real-ti e Transfer Protocol (RTP) announced that the encoding, transmission and decoding of real-time data such as audio and video controls. According to [1] a RTP header includes a 16-bit sequence number that is incremented with each RTP packet. This allows the receiver to detect packet loss in transmission and to bring the packets in the correct order. For reasons of data security, a random number is used as an initial value in the first data packet. According to [1] includes a RTP header is an option that limits of data block in the data stream by setting marker bits to identify.

From [2] called interleaver blocks are known, in which the data line by line rix read in an encoder in a mats and read column by column from the matrix. In a decoder, the entire interleaver block is reassembled before the data contained therein are recovered.

From [3] a redundancy information is (also: redundancy) known by which transmission errors can be compensated. Thus, data to be transmitted (= content data) is additionally provided prior to transmission via a disturbed transmission channel with redundancy information that is generated from the data to be transmitted by known methods. Then, the content data is sent along with the redundancy information via the transmission channel to a receiver. at the receiver, it is now possible to compensate transmission errors such that on the basis of redundancy information, the content data can be reconstructed. These known error correction methods (see [4]) used.

In [5] a method of unequal error protection (UXP) is described by data, said error protection within a data block is varied in that the data are assigned to different redundancy information amounts. According to [5] is a variable number of data packets in a data block, and is indicated in a separate data field of the ÜXP- header, which is assigned to each data packet.

When transmitting data over error-prone channels occur losses of data packets. This is particularly disadvantageous if data packets are lost, each of which includes a marker bit indicative of the data block boundary. In this case, it is necessary prior to a decoding of the data packets, as long as latch the data packets to the positions of the data packets can be reconstructed within the individual data blocks and the boundaries of the various data blocks.

Thus, the invention is based on the object, the reconstruction of the boundaries of the blocks of data easier.

This object is achieved according to the features of the independent claims. Developments of the invention arise from the dependent claims.

To achieve the object, a method for encoding a sequence specified by digital data. A portion of this sequence of digital data corresponds to a data block and comprises a plurality of data packets. At least two data packets per data block each include an identifier, described the position of the data packet within the associated data block by which true will. The data is encoded in consideration of this identifier.

Moreover, the object is achieved by a process for the utmost flexibility of a sequence of digital data. A portion of this sequence of digital data corresponds to a data block and comprises a plurality of data packets. At least two data packets per frame each include an identifier by which the position of the data packet within the associated data block is determined. The data is decoded in consideration of this identifier.

One advantage of the invention is that the positions of the received data packets within the associated data block at the beginning of the data transmission and / or loss of data packets based on the identifier can be determined immediately. This is also a real-time application such as video telephony or any other multimedia application, executes, because the expenses for the temporary storage of the data is greatly reduced. So the size of the buffer for the data can be significantly reduced or even waived in the decoder.

A further development is that the series of digital data a sequence progressively encoded data (= progressive data), such as progressive coded images or image data streams comprising, wherein the forward data can be image data. Progressive data regarding their level of detail staggered, ie initially the image in a coarse resolution is for example. Transfer so that it can be represented, but the details are largely unrecognizable. Stepwise refinement of the image to be transferred, so that as the transmission time, the resolution of the image is getting better.

In an additional development includes the data block redundancy information. Thus, an error correction method Data errors that have occurred during a transfer, correct and the data reconstructed.

Another development is that the basis of the identifier of the data packets, a beginning and an end of the data block are determined.

In an additional development, the data packets each include information about the data block width.

In another development, the identifier and the information on the data block width are alternately, in particular for a predetermined repetition pattern transmitted in a data field. This is advantageous as only a single data field for the transmission of the identification and the information on the data block width is needed and, in spite of the additional functionality does not increase the amount of data to be transmitted.

An additional development is that the number of data packets is specified with identifier such that every nth data packet with the identifier.

Another development is that the number of data packets is specified with identifier such that the data field of every nth data packet includes the identifier and part of the remaining data packets each in its data field, the data block width.

In another development, the predetermined number of data packets containing an identifier of each second data packet.

In an additional development, the data block is an interleaver block. The data for example line by line read into the interleaver block and eg read column by column from the interleaver block and then transferred to the encoder. Is in the data transmission a data packet, that is, a column of the interleaver block is lost, so that data is distributed loss across the rows of the interleaver block. Include the data row redundancy information, these errors can be corrected to a certain number means an error correction process, wherein the amount of redundancy information directly affects the number of correctable errors.

An additional development is that a sequence of the data blocks can be identified, in particular on the basis of a time stamp or by a consecutive number. The time stamp is a digital signature, for example, the transmission time of a date, here the data block indicates.

An additional development is that the identifier for determining the position of the data packet within the data block is a sequence number. The sequence number is, for example, a sequential numbering of the data packets. As an initial value, for reasons of data security a random number or a number "0^λ or "1" can be selected.

In an additional development, a Real-time Transfer Protocol (RTP) is used. RTP provides services avail- able to transmit real-time data such as multimedia data. These services include the award of timestamps and sequence numbers of data packets.

As part of this development, the sequence number of the RTP is used to determine the identifier for determining the position of the data packet within the data block.

An additional development is that a method for unequal error protection, eg UXP, is used. So progressive data within a data block are each provided with a different amount of redundancy information to be considered in particular that the build progressive data of a displayed unit, for example an image, successively, ie in the distribution of redundancy information, the different stages of progression have to be considered. Much redundancy information is to be provided at the beginning of the progressive data conveniently while with increasing detailing always less redundancy information. The number of data packets in a data block, called the data block width, can vary per data block.

To use the same data field of the identifier for determining the position of the data packet within the data block and the data block width, the size of the identifier is preferably adapted to the size of the data field. For example, if the data field for the data block width size of 8 bits and the identifier determined from a 16-bit sequence number of the RTP header, then from the 16 bit identifier an 8 bit identifier generated by omitting the high-order 8 bits will.

Furthermore, an arrangement for encoding a sequence of digital data is given to solve the task. In this arrangement, a processor unit is provided which is set up such that a part of the sequence of digital data is a data block and comprises a plurality of data packets. At least two data packets per frame each include an identifier by which the position of the data packet within the associated data block is determined. The data can be coded taking into account the identifier.

In addition, an arrangement for decoding a sequence of digital data is given to solve the task. In this arrangement, a processor unit is provided which is set up such that a part of the sequence of digital data is a data block and comprises a plurality of data packets. At least two data packets per frame each include an identifier by which the position of the data packet within is of the associated data block determined. The data is decodable by taking account of the identifier.

The arrays are particularly useful for carrying out the processes or the developments described above.

The invention or any training described above may be implemented by a computer program product comprising a storage medium on which a computer program is stored, and that's ablaufbar on a computer executes the invention or development.

Embodiments of the invention are described below with reference to the drawings and explained.

Show it

Fig.l is a sketch illustrating the principle of an interleaver block,

2 is a sketch which illustrates a method for encoding digital data,

3 is a sketch which illustrates a method for decoding digital data,

Fig. The structure of a transmission packet,

5 shows a position determination of the data packets within data blocks,

6 shows the structure of a transmission system,

7 shows a processor unit. In Fig. 1 a diagram is shown which illustrates the principle of function of an interleaver block.

A progressive digital data sequence 101 with data 1-12 is by way of example is divided into three refining steps, wherein the data 1 to 3 the main data, the data 4-7 are less important, and finally the data 8 to 12 in this example, the least significance within the per - sive data sequence 101 have.

An interleaver block 102 includes 3 rows and 6 columns. the data of a refinement step are stored in the interleaver block 102 and generates the respective data of a refinement step redundancy information and stored in the interleaver block 102 with each row of the interleaver block 102nd In Fig.l the interleaver block includes three lines, the first line of the data 1 to 3 with redundant information Rl, R2, R3, achieved in a second line to the data 4 to 7 with redundancy information R4, R5, and in a third row are 8 to 12 provided with redundancy information R6 data. Thus, the data 1 to 3 of the first row of the interleaver block 102 are the most likely (compared to the data of the respective other two lines) can be reconstructed as the first row has been assigned to the largest amount of information redundancy.

In this way, in the interleaver block 102, a re dundanzprofil 110, which is apparent from the described distribution of the data 1 to 12 and the redundancy information generated Rl to R6 within the interleaver block 102nd

Subsequently, the data 1 to 12, together with the redundancy danzinformationen Rl to R6 columns of the interleaver block 102 is read, the contents of the columns are combined to a data packets 103 to 108: The Data packet 103 comprises the data 1, 4, 8, the data packet 104 includes the data 2, 5, 9, the data packet 105 includes the data 3, 6, 10, the data packet 106 includes the redundancy information R and the data 7, 11, the data packet 107 includes the redundancy information R2, R4, and the data 12 and the data packet 108 includes the redundancy information R3, R5, R6.

A data read sequence 109 is thus: {1, 4, 8}, {2, 5, 9}, {3, 6, 10}, {Rl, 7, 11}, {R2, R4, 12}, {R3, R5, R6}.

In FIG. 2 a diagram is shown which illustrates a method for encoding digital data.

A sequence of progressive data 201, the example here consists of a block of data, an encoding unit 202 is supplied, comprising an optimizing unit 203 and a packaging unit 210th First, the result is 201, the optimization unit 203 is supplied and analyzed there. The analysis provides a structure of the progression of the data, based on the size of an interleaver block 204 and redundancy and a profile 205 determined. The redundancy profile 205 is part of administrative data 206 which are necessary for evaluation of the interleaver block 204 at the receiver. In the optimizing unit 203 are redundant information 207 for the administrative data 206 and redundancy information 208, 209 generated for the digital data 201, wherein the more redundancy information is provided, the more important the data is, ie inter alia dependent on the finishing stage of progression (see the above).

In the interleaver block 204 out the administrative data is stored 206 and this most redundancy information associated with 207 to eg. Correct many transmission errors as possible can. Next, the interleaver block 204 201 and associated redundancy information 208 and 209 filled line by line with the progressive data. Is the interleaver block 204 filled with data and redundancy information, as the content of the interleaver block 204 as explained with reference to FIG. 1, read column by column and fed to the packaging unit 210. In the packaging unit 210 packing the contents of a column 211 of the interleaver block 204 is shown as an example. Thus, the data packet 211, which corresponds to the data of the column 211, provided with a header 217 and combined to form a data packet 218, which is referred to as transmission packet 218 below.

The header 217 includes a field 219 that contains a sequence number for the transmission packet 218th In addition, the header 217 includes a field 220 in which an alternate identifier that the position of the data packet 211 can be determined within the respective interleaver block 204, or a width of the respective interleaver block 204 is specified. Also, the header 217 includes a field 221 in which a time stamp is specified for the respective interleaver block 204, each interleaver block of an image sequence is replaced by a different value as a timestamp, so that individual interleaver blocks are distinguishable. Here, it should be noted that the sequence of digital data 201 includes a plurality of progressively encoded units, preferably wherein each such unit a is stored in an interleaver block. The interleaver blocks can vary in size depending on progressively coded unit. Preferably, individual images of the sequence of digital data 201 are progressively encoded.

Similar to column 211, the remaining columns 212 to

216 of the interleaver block 204 packaged to transfer packets 222-226 and transmitted together with transmission packet 218th This results in a coded data string 228 corresponding to a data block 227th This data block 227 is also referred to as a transmission block. In Fig. 3, a method for decoding digital data is shown.

A sequence of digital data 301 includes a data block 302 comprising a plurality of transmission packets 303-308, each transmission packet having a header and a data packet.

So 303 includes the transmission packet a header 309 and a data packet 315, the transmission packet 304 a header 310 and a data packet 316, the transmission packet 305 a header 311 and a data packet 317, the transmission packet 306 a header 312 and a data packet 318, the transmission packet 307 a header 313 and a data packet 319 and the transmission packet 308 has a header 314 and a data packet 320. the series of digital data which has been received in particular via a disturbed transmission channel is supplied to a decoding unit which includes an unpacking unit 322, and an evaluation unit 325th

First, the transmission packets 303 are fed to the unpacking unit 322 to 308 and the data packets 315-320 unpacked. For the unpacking unit 322, the unpacking of the data packet 315 is shown as an example of the transmission packet 303rd firstly the header 309 of the transmission packet 303, the column position of the data packet 315 within the interleaver block 324 it is evaluated in accordance with this header 309, in particular with reference to the identifier included in the header 323 is determined. The problem of the position determination is explained in detail in Figure 5.

The transmission packet 303 is as long as cached in the unpacking unit 322, to the position of the data packet 315 can be determined in the interleaver block 324th

Was to determine the position of the data packet 315 within the interleaver block 324 possible, the data packet is 315 stored as a column in the interleaver block 324 the evaluation 325th Accordingly the interleaver block is 324 columns filled with the data packets 316-320.

The contents of the interleaver block 324 is processed line by line, for example, read out the image information. Data include 326 administrative information enabling a redundancy profile can be designed for 327 interleaver block 324th With the redundancy profile is the line between content information, whether of an administrative nature

(See data 326) or pure image data (see data 331) is determined.

If the data packets lost due to faulty transmission 315-320 of interleaver block 324 for example, so these errors can (to a certain frequency, whose upper limit is determined by the amount of the Transferred redundancy information) through an error correction method in the evaluation unit 325 help the Redundanzinformatio- NEN 328, are corrected 329 and 330, with eg. (only) the loss of the data packet 316 requires that a column of the interleaver block 324 needs to be restored, which is possible for complete rows in the illustrated arrangement of the redundancy information, in particular can be ensured due to the progression of data that important data can be reconstructed in the data packet 316, may be omitted unimportant if necessary, without the functionality of the process would be jeopardized. The read digital data sequence 332 may in an image decoder, especially one for a Bildkompri ierungs standard, such as MPEG1,

MPEG2, MPEG4, H.261, H.263, H.26L, working decoder, be further processed.

In FIG. 4, the construction of a transmission packet is illustrated. A transmission packet 401 of a transmission block 402 includes a header 403 and a data field 404 that contains a data packet 405th The header 403 includes a Sequence number field 406, in which a sequence number 407 of the transmission packet is specified 401, a flag field 408, in which either an identifier 409 for determining the position of the data packet 405 within the data block 413 or widths te 410 of the burst is indicated 402 and a

Timestamp field 411, in which the value of 412 a time stamp of the transmission block is specified 402nd

In FIG. 5, a position determination of the data packets within data blocks is shown an identifier.

Below is assumed according to the nomenclature of the preceding figures of a position determination of the transmission packets within the transmission blocks. The transmission block includes a plurality of transmission packets, each transmission packet has a header and a data packet (see description of Figure 2). A data block on the other hand results from the data packets of the respective block. Thus, the frame includes the transmission packets (see Figure 4, 401), including their respective header (see

Figure 4, 403). The information in this header is essential to the mentioned position determination.

A data sequence 501 comprises frames 502, 503, 504, and 505, wherein the transmission block 502, transmission packets

506-513, the frame 503 transmission packets 514-519, the frame includes 504 transmission packets 520-525 and the transfer block 505 transmission packets 526-529. The structure of each transmission packet is described in Figure 4. For the nomenclature of the individual fields is therefore made to the description of Fig.4.

Belonging to the transmission block 502 transmission packets 506-513 are each in the time stamp field 411 with a time stamp value "A^Λ in belonging to transmission block 503 transmission packets 514-519 are identified respectively in the time stamp field 411 with a time stamp value "B" records, belonging to transmission block 504 transmission packets 520-525 are each marked in the timestamp field 411 with a time stamp value "C" and belonging to transmission block 504 transmission packets 526-529 are each marked in the timestamp field 411 with a time stamp value "D". The transmission packets 506-529 include in their sequence number field 406 a consecutive sequence number 407 exemplarily begins for the transmission packet 506 with "10" and for the transmission packet 529 with "33" ends.

In their respective marking field the transmission packets include having an even sequence number 506, 508, 510, 512, 514, 516, 518, 520, 522, 524, 526, 528, the identifier for determining the position of the transmission packet within the associated transfer block, in which case the identifier from the sequence number of each first transmission packet in the frame consists, ie the transmission packets 506, 508, 510, 512 include the identifier field 408 is "10", the transmission packets 514, 516, 518 include the identifier field 408 is "18", the transmission packets 520, 522, 524 include the identifier field 408 is "24" and the transmission packets 526, 528 include the identifier field 408 is "30". In the tag field 408 leg stop transmitting packets having an odd sequence number 507, 509, 511, 513, 515, 517, 519, 521, 523, 525, 527, 529, the respective transmission block width 410, ie, the transmission packets 507, 509, 511, 513 include in the marking field 408 has the value "8" for the width of the transmission block 502, the transmission packets 515, 517, 519 include the identifier field has the value "6" for the width of the transmission block 503, the transmission packets 521, 523, 525 include the identifier field the value "6" for the width of the transmission block 504 and the transmission packets 527, 529 contain the value "4" for the width of the transmission block 505 in the identification field 408th In Fig. 5, it is assumed that the transmission of packets 507, 508 and 512 of the transmission block 502, the transmission packets 514-519, so the whole transmission block 503, the transmission packets 521 and 525 of the transfer block 504 and the transmission packet 526 of the transmission block 505, in the data transmission have been lost. Lost transmission packets are marked in Fig. 5 by an "X" in each sequence number field.

Since the last transmission packet 519 of the burst was 503 not received and because the frames have 502-505 different frame widths, it is not possible to determine to "C" to the beginning of frame 504 of the change in timestamp value "B" because both the transmission packet 520, as well as one of the Ü bertragungspakete 514-519 the first transmission packet in frame 504 could be. Since the boundary between frame 503 and frame 504 is not clearly determined, may not described above identifier the received transmission packets 520, 522, 523 and 524 their

Position can not be clearly assigned within the burst 504th Is also the last transmission packet 525 of the transmission block 504 and the first transmission packet 526 of the transmission block 505 lost, can untagged also the end of the burst 504 from the

Change the timestamp values ​​"C" can not be clearly determined to "D", so that it is necessary, more than one frame temporarily before the data can be decoded.

With the identifier in the identifier field it is now possible, the sequence number "24" and the code "24" to compare upon receipt of the transmission packet 520 with each other, it follows that this is the first transmission packet of over- tragungsblocks 504 because the identifier "24" with the sequence number "24" matches. Thus, the received transmission packets can 520, 522, 523 and 524 of transmission blocks 504 are deposited directly into the correct positions within the transmission block 504 and there is no need to cache these transmission packets longer. Is also the transmission packet 520 with the sequence number "24" lost, so is composed of the identifier "24" of the received transmission packet 522 with the sequence number "26" immediately find the location of this transmission packet in the transmission block 504 will be charged: 26 - 24 = 2 , ie there are in the frame 504, two transmission packets 520 and 521, the received transmission packet 522 is thus the third transmission packet of the transmission block 504. in this case, no further caching of transmission packets of the burst concerned is necessary.

In Fig. 5 has been selected as an identifier, the sequence number of the first transmission packet in each frame. Other options are to use as an identifier to the distance from the first or last transmission packet in each frame.

As a further embodiment, the 8-bit data field for the frame width of UXP is used to alternately indicate the frame width and the identifier in the transmission packets. The identifier is determined from the 16-bit sequence number of the RTP by the sequence number of the first transmission packet of the respective transmission block of 16 bits is reduced to 8 bits. This is achieved, for example, that the most significant two digits of the hexadecimal codes are deleted, eg from 0xDC36 to 0x36.

In FIG. 6, the construction of a transmission system S is shown. The transmission system S includes a camera K, an encoder C, one defective (faulty) transmission channel T, a decoder D, and a display device F. image data generated by the camera K, are in the Encoder C encoded on the disturbed transmission channel Ü transmitted by the decoder D decoded and displayed by the display device F. In particular, the encoder C and / or D, the decoder operates according to a compliant Bildkomprimierstandard, such as MPEG1, MPEG2, MPEG4, H.261, H.263, H.26L. Encoders and / or Deocder work especially considering the method.

In Fig. 7 a processor unit PRZE. The processor unit PRZE includes a processor CPU, a memory MEM and an input / output interface IOS which is used via an interface IFC different ways: via a graphical interface, an output is displayed on a monitor MON and / or to a printer PRT output. An entry made via a mouse MAS or a keyboard TAST. The processor unit PRZE also has a data bus BUS which ensures the connection of a memory MEM, the processor CPU and the input / output interface IOS. Furthermore, additional components can be connected to the data bus BUS, eg additional memory, data storage (hard disk) or scanner.

Bibliography :

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[2] A. Falkenberg: "encoding / decoding device for

Performing a block-interleaving / deinterleaving, "Patent DE 198 44 140 C1

[3] Duden computer science, S. 553, Duden Verlag 2001

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