KR100327684B1 - Image Display Variable Length Codeword Data Stream Processing Unit - Google Patents

Abstract

In a digital television signal processing system, a specific code word, packet alignment flag (PAF), is inserted into the MPEG code word bit stream to signal the presence of a picture group (GOP). The PAF immediately precedes the picture start code word for the " I " frame initiating the GOP. When a PAF appears, the data packet in the configuration ends because the GOP starts at the packet boundary. This termination produces shortened packets less than the prescribed number of code words needed to complete the data packet. The last word of each packet is denoted as a word that allows further combination of data packets and respective headers. A null (zero bit) word is filled in an incomplete data packet to form a complete data packet with a prescribed number of words.

Description

Image Display Variable Length Codeword Data Stream Processing Unit

Field of invention

TECHNICAL FIELD The present invention relates to the field of digital signal processing, and more particularly, to an apparatus and method for processing a data stream including a transport packet for transmitting encoded MPEG data in a high definition television system.

Background of the Invention

U.S. Patent 5,168,356 to Acampora et al describes a processing system for processing MPEG variable length coded high definition television (HDTV) signals. MPEG is a standard code format established by the International Organization for Standardization. The standard is described in the Coding for Moving Pictures and Associated Audio for Digtal Storage Media document of ISO / IEC DIS 11172 of the International Organization for Standardization, published November 23, 1991, which is a reference for describing the general code format. Are incorporated in this Person. Acampora et al. In the system of s, the codewords are prioritized to reflect high and low rank information in the data stream. The codeword datastream packs codeword data into transport cells, each of which consists of a header and packed data payload sections, and the data of high and low ranks. Sent to a transport processor providing a stream output.

The main function of the transmit processor is to pack variable length codeword data generated by a prioritization priority processor into packed data words. The measurement of a pack word called a data packet is started with the transmission header at the beginning.

The transport packet format improves signal recovery and resynchronization at the receiver by providing header data in the data stream that allows the receiver to determine re-entry points in case of loss or destruction of transmission data, eg after signal degradation due to transmission channel disturbances. Let's do it. Data synchronization in the MPEG decoder is easily done by a picture group (GOP) starting at the packet boundary. As is known, a GOP is one or more series of pictures or frames for random access assistance into a coded video bitstream sequence. Resynchronization is facilitated by responding to the intracoded I frame picture start codeword and placing the picture start codeword at the packet boundary in a system conforming to the MPEG standard.

Summary of the Invention

According to the principles of the invention, in a system for transmitting variable length codewords (e.g. MPEG codewords) in a data packet, an unfinished data packet with words smaller than a prescribed number generates a fixed length packet and the defined codeword appears. Packed with non-operating "zero words" to define an inter-packet boundary.

In the disclosed preferred embodiment, a particular codeword, packet alignment flag (PAF), is inserted into the MPEG datastream to announce the start of a group of pictures (GOP). The PAF immediately precedes the picture start codeword for the intracoded " I " frame initiating the GOP. PAF indicates the impending appearance of a picture start codeword, and has one click cycle while certain "housekeeping" functions are performed before the picture start codeword appears at the beginning of the next packet. The housekeeping functions include, for example, an accumulator reset function, a header data check function, and a function for generating a final word indicator for the data packet being constructed when the PAF is displayed. When the PAF appears, the data packet in construction is terminated because the GOP is intended to be initiated at the packet boundary. This termination can result in a shortened packet containing packed words smaller than a prescribed number. Null words (words of zero bits) are appended to the shortened data packet to define an inter-packet boundary in which the picture start codeword can appear, forming a complete data packet with a prescribed number of words. Is filled. Thirty 32-bit fixed length words form a data packet, which begins with a 32-bit header.

1 is a block diagram of a portion of a video signal encoder comprising a data word controller, a data packer and a data / header combiner device in accordance with the present invention.

2A, 2B, and 2C show details of the word controller and data packer of FIG.

3 is a truth table relating to the operation of the word status controller shown in FIG. 2A.

4 shows details of a pack data assembler network.

5 to 16 show an example of the final word generation.

17 shows details of the data and header combiner unit shown in FIG.

FIG. 18 is a state diagram related to the operation of the state controller shown in FIG.

19 is a block diagram of an HDTV encoding system including an apparatus according to the present invention.

20A and 20B are illustrations of a series of image fields / frames of an encoded video signal.

FIG. 21 is a diagram showing a data block generation developed by the encoding / compression apparatus of the system of FIG.

FIG. 22 is a general illustration of the data format provided by the encoding / compression device of the system of FIG. 19. FIG.

Detailed description of the drawings

1 is a block diagram of a data packer 12 and a packed data word controller 10 of a transfer processor. As mentioned above, the main function of the transfer processor is to pack variable-length codeword data into fixed-length (eg 32-bit) data words. The thirty accumulated data words make up the data packet whose opening is ultimately in the transport header. Such a transmission processor may be used in a processing system that processes MPEG compressed video signals as will be discussed next with respect to FIG. 19. Further features of MPEG formatting and processing are described in relation to the 20th, 21st, and 22nd degrees.

Controller 10 monitors the accumulation of length data words for a packet allocation flag (PAF) for the completion of assembled 32-bit data words and the completion of 960-bit data packets from a stream of variable length codewords. The length data is a six bit parallel word that matches a variable length codeword defining its length. The binary value of the length word represents the number of bits of the corresponding variable length codeword that actually represents the MPEG codeword to be transmitted. Each variable length codeword appears on a 32-bit wide bus with a variable number of significant bits (1 to 32) representing the MPEG code.

The PAF is generated by the input processor 14 and appears in one codeword immediately before the first MPEG I frame picture start codeword of the picture group. The PAF may be generated by detecting the presence of the I frame picture start codeword by a digital comparator. Unit 14 also has a signal delay network that processes the picture start codeword and the PAF, so that the PAF occurs in a codeword click cycle immediately before the I frame picture start codeword. The delay network ensures that the output signals applied to units 10 and 12 are properly time synchronized.

The word address is passed to the data packer 12 receiving the variable length codeword for packing so that the input variable length codewords are properly concatenated. A word control signal is also provided to the packer 12 to describe the Short Word, to indicate the last word in the packet, and to properly align a series of thirty pack data words with associated transport headers. The controller 10 tracks the packet completion by accumulating the binary values of the length words. The packet completes when 960 bits accumulate. The starting point or initial point of the count is provided by the appearance of a PAF that resets the internal accumulator in controller 10.

The packer 12 receives a variable length code word (VLC) over a 32-bit parallel data bus. Valid bits are packed into 32-bit words under signal control from the controller 10. The connection is arranged to provide the final MPEG bit serial transmission order. Pack data from unit 12 is provided to the input FIFO data buffer 16 and header combiner 15 of the data at variable word rates. The combiner 15 also receives a data write enable signal from the packer 12 which enables writing of valid data into the internal FIFO data buffer 16. The data packet is fully formed when 30 said words have been transmitted unless the PAF forces a short packet. The last word indicator generated by the packer 12 indicates the 13th word in the normal packet in this example, or the last word in the packet reduced to the presence of the PAF. do.

A packed data word is sent to the data / header combiner 15 whenever it is available. Similarly, a transport header is sent from the header generator 18 to the input FIFO header buffer 17 of the combiner 15 whenever the header is available. The header generator 18 is configured to form a header. The information used by is obtained from input processor 14 and word controller 10. The header write enable signal indicates that the header is available and can write the header to the FIFO 17. The combiner 15 prefaces the appropriate headers for each pack data payload and sends the final transport packet or block to the output rate buffer as shown in FIG. The combiner 15 also provides an output data ready signal to signal that the pack data word or transfer header is ready to be transmitted. The header indicator signal indicates the clock cycle in which the header is sent. This signal functions as a transport packet boundary marker so that subsequent operations such as forward error correction (FEC) can be applied to the transmitting cell as appropriate.

Each header contains information about the data in the data packet with which the header is associated. The header information assists in assembling and synchronizing data at the receiver and includes information such as service type (eg audio, video, data), frame type, frame number and slice number. This type of header and its processing is described in Acampora et al. U.S. Patent No. 5,168,356, describes a HDTV digital signal processing system using MPEG signal coding.

The data packet may comprise less than 30, for example 1 to 29 pack data words in this embodiment. The PAF provided by the input processor 14 appears immediately before the picture start codeword of an I-coded intra frame at the beginning of the GOP, as described in connection with FIGS. 20-22. The picture start codeword for an intracoded frame always starts a new packet, and the immediately preceding PAF indicates the end of the data packet and the start of a new packet. Such packet alignment of picture start codewords is beneficial for high speed acquisition of data streams at the receiver. When a PAF is generated in forming a fixed length word, a shortened data packet is formed. The remaining bits in the constituent pack word are filled with a number of "zero bits" (1-31) in the data packer 12. Similarly, the remaining words in the data packet are filled with " zero words " (1 to 29) in the combiner 15 to maintain the transport packet size. The need to fill the zero word is indicated by the appearance of the final word indicator before 30 data words are sent to the combiner 15.

Proper identification of the last word in the data packet is important. The final word ensures proper registration of the packet, together with the associated transport header. The final word also describes the filled packet in the MPEG group of picture boundaries (intracoded frames) that are critical for resynchronization in the television receiver / decoder, such as after a channel change. Determination of the final word is not a trivial matter and depends on the particular packet state awareness, such as whether the packet is terminated and if there is data partitioning into the next packet. The last word is a word formed in the current clock interval or a word to be formed in the next clock interval.

Specific examples of the final word formation are as follows. If no PAF exists when the packet is complete, the last word (31st word in this example) is the last word and is indicated by the last word indicator. This is an example of a "true" final word. PAF can be generated when a packet is completed without bit splitting into the next packet. In other words, the word ends on a packet boundary. The last word of the completed packet is marked as the last word since it is actually the last word. This is an example of another "true" final word. PAF may also occur when a packet completes with some bit splitting into the first word of the next packet. In this case, two consecutive final words are formed and displayed. The last word of the completed packet is marked as last ("true" last word), and the first word of the next packet is marked as last, because PAF forces the packet shortening. In the latter case, the last word that appears before 30 words are sent fills a "zero word" to complete the packet. Another example of the final word is as follows. PAF can be generated at once when an incomplete packet is in construction. If the inner word completes with some bit division into the next word, some words become the final word. A particularly difficult situation arises when an incomplete packet is being constructed and the inner word completes without bit splitting into the next word. The inner word may be sent to the data / header combiner before subsequent data (ie, the appearance of a PAF) indicates that the inner word is the last word too late to be properly marked as above. In this case, a zero word called a "pseudo" final word is generated and represented as the final word. The pseudo final word is formed entirely of zero bits in contrast to the divided (unfinished) final word partially filled with zero bits. Such and other examples are shown in FIGS.

16th degree is described.

Important features of the disclosed system, which will be described below, in addition to generating and indicating the last word in a data packet, are specific to the generation of a zero length PAF that signals the beginning of a GOP, the generation of the necessary pseudo final word, and the final word generation change Signal generations.

FIG. 2A shows details of the controller 10 of FIG. The controller includes an accumulator 20 of the feedback device with module 960 circuit 22. The buffer register 23 is included in the feedback loop to maintain a new cumulative value at the end of each length input cycle. The input PAF and length word are transmitted to the module unit 22 and the accumulator 20 through the input register 24, respectively. The value of the length word is accumulated continuously by the unit 20, and the feedback combination of the accumulator 20 and the module 960 unit 22 sets the length of the packet to 960 bits. The accumulator output from the register 23 indicates the bit position in the packet and is sent to the packet state controller 25.

The packet state controller 25 also receives a PAF from the input buffer register 24 and generates an output signal necessary to generate a write command in the word state controller 26. The packet completion output signal is output to the word state controller 26 when the accumulator bit count is greater than or equal to 960. An output Remnant signal is generated by the controller 25 when the accumulator bit count is not on the word boundary (ie when the bit count is not equal to an integer multiple of 32). A true zero output signal is generated when the accumulator bit count is zero. The signal is only important for determining the exact formation of the final word when a PAF is provided. The logic circuit for generating the signals is shown in FIG. 2B described below.

The accumulator 20 idles and maintains the last bit count value when a zero length null codeword, i.e. a zero value length word indicating the presence of a NO-OP codeword, is received. One exception to this rule is that PAF always forces the accumulator value to zero regardless of the bit count.

Another exception is raised when a packet completes exactly on packet boundaries (ie when the accumulator count is 960). In the next clock cycle, the accumulator count is corrected through the module 960 unit 22 to the binary value of the next length word. The packet completes when the accumulator count is greater than 960.

In FIG. 2B, the 10 bit accumulator output representing the accumulated length is represented by I0 to 19. If the accumulated length of the pack codeword is 960 or more, the packet is completed. This condition is indicated when the four MSB bits, 16 through 19, of the accumulator are in a logic 1 state as applied to the AND gate 30. True zero is indicated when all ten accumulator bits are in a logic zero state as applied to the OR gate 31. The " no remaining " condition is indicated when the five LSB accumulator beaters, 10 to 14, are in a logical zero state as applied to the OR gate 32. The data packer word address is

It is formed in response to six LSB accumulator bits, 10-15. AND gate array 34 creates a logical zero state (word address reset) at the word address when the packet alignment flag (PAF) is encountered.

FIG. 2C shows details of the data packer 12 of FIG. Variable length codewords are provided to a data shifter 35. The shifter may be a barrel shifter such as Texas Instrument Type 74 AS8838. In order to properly place the valid bits of the variable length codeword for concatenation, the LSB subset of the length accumulator output is output from the packet state controller 25 and provided to the data shifter as a word address. When a 32 bitword is formed from a variable length codeword, the pack word is transferred to the retention register 36. The availability of packed data words is flagged by a word ready signal generated by register 36 so that the words can be sent to data assemble network 37. The data assembler 37, together with the data write enable and the final word flag, outputs the packed data word to the FIFO buffer embedded in the data / header combiner 15 of FIG. Control signals WEN1, WEN2, and WZERO are used.

Insertion of the next transmission header into the synthesized data stream follows the last word transmission of the packet, so that the header of the next packet is inserted after the last word of the current packet. The accumulator output (Figure 2A) is used by the header controller to indicate the location of any codeword in the packet, which location can be described in the entry point field in the header. Generation of flags and final word indicators that enable data words to be written to the fifo buffer include logic array inputs (PAF: Packet Alignment Flags) associated with word status control 26 and data assembly network 37, PC (packet completion), The operational state of generating the final word in response to TZ (True Zero) and REM (residue, word division indicator) is shown. Output signal formation from the data assembly network 37 is facilitated by the output signal from the controller 26 provided through the buffer register 28. The signals are a write enable signal representing the last word that appears in the next clock cycle.

(WEN1), a write enable signal WEN2 that represents the last word that appears in the current clock cycle, and a zero write signal WZERO that generates a pseudo last word. The pseudo final word is generated when the PAF matches a packet configuration present in the inner codeword boundary of an incomplete packet.

Table 1

Word Status Controller Status

Note 1: The last word flag on the current word is signaled by write enable 2.

Note 2: The last word flag on the word in the next clock is signaled by write enable 1.

Note 3: The construction of the pseudo word is signaled by write zero and flagged by write enable 1.

The truth table that generates WEN1, WEN2, and WZERO

As further described in connection with FIGS. 5 through 16, examples of various operating conditions (cases 1 through 6 in table 1) are shown in FIG. 3. The algorithm for Table 1 is provided in Appendix A. The output signal from the controller 26 is provided as an output word control signal to the output buffer register 28 before being provided to the data assembling network shown in FIG.

The data assembly network of FIG. 4 includes the output network of the data packer 12 of FIG. The data assembler includes AND logic gates 42 and 44, OR logic gate 46, and D flip-flops 43 and 45 arranged as shown. The packed 32-bit wide data word is sent to the data FIFO via an AND logic gate 42 and the word ready signal from the preceding packer circuit is sent through an AND logic gate 44 to provide the data FIFO 16 of FIG. It becomes a data write enable signal. Data write control signals WEN1, WEN2, and WZERO from the packed word state controller (Fig. 2A) are applied to flip-flops 43 and 45 and logic gate 46 as shown. WEN2 represents the last word flag associated with the current word, and WEN1 represents the last word flag associated with the word of the next clock cycle. The WZERO control represents the configuration of the pseudo final word (case 1 of Table 1) flagged as the final word by WEN1. In this case, all all zero words, referred to as pseudo final words, are inserted into the packed data word stream and written to the data FIFO 16. The word ready input signal to assembler gate 44 is provided by retention register 36 (FIG. 2C) to signal the availability of a packed 32 bit word.

The following description relates to examples of the final word generation described by FIGS. 5 to 16. Some of these examples show zero length NO-OP word effects consistent with preceding and following PAFs.

5 and 6 show a change in case 5 of table 1. FIG. In FIG. 5, a packet is completed with division into the next packet (ie, accumulator bit value greater than 960). In FIG. 6, a packet is completed on the packet boundary (i.e., an accumulator value such as 960) without splitting or remaining into the next packet. In all cases, the last word flag is generated upon packet completion. This occurrence is independent of True zero and residual indication since no PAF is present. However, true zero and residual indication should be considered when PAF is present.

7 and 8 illustrate the case 2 of Table 1. In FIG. 7, PAF is generated immediately after the packet is completed without splitting, followed by a 32-bit picture start codeword. 8 is similar except that three INTERVENING zero length non-operating (NO-OP) code words precede the picture start code word. In both figures, the PAF corresponds to the packet completion signal and to the end of the packet with no splitting into the next packet. 7 illustrates a more general case immediately followed by a 32 bit long Picture Start codeword. 8 shows that intervening NO-OP words are allowed.

9 relates to case 6a of Table 1 in which the PAF does not match the packet completion signal. PAF occurs after a packet is completed, followed by a picture start codeword followed by a NO-OP word without segmentation. In this case, the final word mark is related to the packet completion signal but there is no final word mark related to the PAF because in this case the true zero mark is related to the accumulator idle of zero.

10 and 11 illustrate case 1 of Table 1. In FIG. 10, PAF is generated just after the packet is completed, followed by the picture start codeword by segmentation.

FIG. 11 is similar to FIG. 10 except that the intervening NO-OP word precedes the picture start codeword. Two final word indicators are generated in the packet completion period, and the other final word indicators are generated in one clock period following the PAF due to splitting.

12, 13 and 14 show Case 3 of Table 1. FIG. In this example, the PAF sometimes occurs during packet formation, but does not occur on the word boundary (ie, there is a split into the next word) and does not match the packet completion indication. The final word signal normally occurs after the PAF in the next clock period as a result of some started words due to division.

In FIG. 12, a PAF is generated after a packet is completed, followed by a segmentation and several NO-OP words followed by a picture start codeword. In FIG. 13, the PAF is generated as soon as the word is completed, followed by the picture start codeword with division. In FIG. 14, the PAF occurs after the word is completed and after some codewords have been split.

15 and 16 show case 4 of Table 1, which relates to the need to generate a particular type of final word, pseudo final word. This case is associated with a PAF that occurs immediately after the word is completed or some time later, without partitioning, i.e. with a word boundary of many times 32. The premise of this case is that it occurs prior to the recognition that the completed word was the last word. All zero zero pseudo last words are formed and generated. This is because MPEG allows for any preceding number of zeros before the start codeword and ensures that the picture start codeword is the next picture start codeword by generation of a PAF. Also in this case, the zero bit word is filled by the data / header combiner in the packet balance. Since one zero word is generated and pseudo marked as the final word, the combiner generates one word in this case. In FIG. 15, PAF occurs immediately when a word completes without division, followed by a picture start codeword.

In Figure 16 the word is completed without division and is followed by the intervening NO-OP word. The picture start codeword follows after the PAF is generated.

17 shows additional details of the data / header combiner 15 (FIG. 1). The header component is written to the header FIFO 70 in response to the header write enable signal each time the headers are generated by the header generator 18. Similarly, a pack data word is written to data FIFO 72 in response to a data write enable signal whenever a pack data word is generated by data packer 12. The last word indicator generated in the data packing process is accompanied by the last word in the packet to indicate whether or not the last word is the 30th word. The header and data outputs of units 70 and 72 are multiplexed on a common bus by multiplexer 76 and applied to output register 78. The register 78 is shown in FIG.

Data ready signals, packet data and headers, and header indicators are provided to rate buffers 713 and 714. Multiplexer 76 may generate a zero word on the command in response to a zero generation signal from FIFO state controller 74.

FIFO units 70 and 72, multiplexer 76 and output register 78 are controlled by controller 74 which is a state machine. After a power-on or similar restart, controller 74 waits for an available header. The header is provided on a common bus of the multiplexer 76 along with a data preparation indicator and a header indicator. Controller 74 then provides a data FIFO that extracts the available data until the last word indicator appears. Each data transferred is accompanied by a data preparation indicator that is passed to output register 78. If 30 data words are provided after the last word indicator appears, controller 74 re-examines the available information head FIFO 70. If less than 30 data words are provided, controller 74 instructs multiplexer 76 by a zero generation instruction to generate zero words for the balance of the packet. All zero generation words are accompanied by data preparation indicators. If no header or data is sent, controller 74 instructs multiplexer 76 to output a zero word without any data preparation indicators during the data unavailable period. As described above, a pull chart (state diagram) for explaining the state machine driving operation of the combiner 15 is shown in FIG. The data preparation indicator and the header indicator are output via the output register 78.

Are sent to the rate buffers 713 and 714 of FIG. This indicator informs the rate buffer that data and header information is present on the bus, and maintains header / data registration to facilitate forward error correction (FEC) coding and subsequent data interleaving for the rate buffer. In this system, the FEC and interleaving processes first need to send a header, i.e. send the header to the rate buffer before the data packet described by the header. Empty flag signals transmitted from the header FIFO 70 and the data FIFO 72, respectively, indicate that the state machine controller 74 is idle (idle) because no header or data words are provided. This condition is shown in the figure of FIG. 18 for the " no header " and " no word " When the associated read enable signal is sent to the header FIFO 70 or the data FIFO 72, respectively, the header / data selection signal from the controller 74 is output from the header 70 from the unit 70 or from the unit 72 to the signal bus. Command to the multiplexer 76 to switch the data output of the input to the input of the output register 78.

The output buffer 78, with zero words appended to an unfinished shortened packet to produce a defined 30 word data packet, is considerably larger than the preceding header buffer 70 and data buffer 72. These buffers effectively continue to receive and process data without interruption. The uninterrupted operation greatly simplifies the timing and synchronization function, i.e. eliminates the disadvantages of clock stop / start synchronization.

By adding the required null words as described, using packets of a completed prescribed length effectively done facilitates searching and synchronization under any data condition as found in variable length codeword systems. The start codeword, in particular the I frame start codeword, is a specific resynchronization point in the MPEG compatible data stream. The start codeword appears in the packet boundary, and its development is effectively done in the disclosed system by using a null word of zero bits to complete the concatenated data packet and define the packet boundary. The MPEG standard allows any number of zero words before the start codeword, and the receiver / decoder ignores null words of zero bits. In this example, output buffer 78 is large and time-elastic, thus being a convenient means of performing a null word packing operation. In this regard, it is noted that very little time (eg, one clock cycle) can be used for null word packing between the appearance of a packet alignment flag and the appearance of a picture start codeword in a packet boundary.

19 shows an example of an HDTV encoding system which can use the apparatus according to the invention in the transmission processor part. 19 illustrates a system for processing a single video input signal, it should be understood that the luminance and chroma components are processed separately and that the luminance motion vectors are used to produce the compressed chroma components. The compressed luminance and chroma components are interleaved to form a macroblock before codeword priority analysis. Further information regarding the system of FIG. 19 is disclosed in US Pat. No. 5,168,356 by Acampora et al.

The image field / frame sequence shown in FIG. 20A is applied to circuit 705 for rearranging the fields / frames according to FIG. 20B. The rearranged sequence is applied to a compressor 710 which generates a compressed frame sequence coded according to the MPEG format. This format is metrology and is shown in abbreviated form in FIG. The MPEG hierarchical format includes a plurality of layers, each with header information. Nominally, each header includes a clause that adds a start code, data associated with each layer, and header extensions.

When referring to an MPEG signal generated by the system, it is meaningful that (a) successive picture fields / frames of the video signal are encoded according to I, P, B coding sequences and (b) data coded at the picture level. Is encoded into an MPEG slice or a group of blocks having a different number of slices per field / frame and a number of macroblocks per slice.

I code frames are intraframes compressed so that only I frame compressed data is needed to play back the image.

(intraframe) Frame. The P code frame is coded according to a forward motion compensated predictive method in which the P frame code data is generated from a current frame and an I or P frame occurring before the current frame. B code frame data is generated from I and P frames occurring from the current frame and before and after the current frame.

The coded output signal of this system is box string (L2).

It is divided into a field / frame group or picture group (GOP) shown in (Fig. 22). Each GOP L2 includes a header followed by division of picture data. The GOP header contains data related to horizontal and vertical picture sizes, aspect ratios, field / frame rates, bit rates, and the like.

The picture data L3 corresponding to each field / frame includes a picture header followed by the slice data L4. The picture header includes the field / frame number and the picture code type. Each slice L4 includes a slice header followed by a number of data blocks MBi. The slice header contains the group number and the quantization parameter.

Each block MBi L5 represents a macroblock and includes a header followed by a motion vector and coded coefficients. The MBi header includes a macro block address, a macro block type and a quantization parameter. The coded coefficients are shown in layer L6. Each macro block includes six blocks including four luminance blocks, a U chroma block, and one V chroma block. The block represents, for example, an 8 × 8 pixel matrix in which discrete cosine transform (DCT) is performed. The four circuit blocks are a 2x2 matrix of consecutive luminance blocks representing a 16x16 pixel matrix. Chromaticity (U and V) blocks represent the same entire area as four luminance blocks. In other words, prior to compression, the chroma signal is subsampled by two horizontal and vertical related factors for luminance. The data slice corresponds to data representing a rectangular part of the image corresponding to the area indicated by the continuous macroblock group. The frame includes a raster scan of 360 slices of 60 vertical slices and 6 horizontal slices.

The block count is provided by the DCT one block at a time. DC coefficients occur first, followed by each DCT AC coefficient in order of relative importance. The end of the block code (EOB) is added to the end of each successive data block.

In FIG. 19, data from compressor 710 is prioritized by prioritizer 711 before providing it to transport processor 712, which divides the data into high order (HP) and standard order (SP) components. Is processed. The components are combined through rate buffers 713 and 714 and sent to error coding units 715 and 716, respectively. The rate buffer temporarily stores pack data and headers for continuous extraction by the FEC error coding network. Rate controller 718, in conjunction with buffers 713 and 714, adjusts the average data rate provided by compressor 710. The signal is then connected to a transmit modem 717 where the HP and SP data quadrature amplitudes modulate each carrier within a standard 6 MHz NISC television channel.

Appendix A Final Word Generation Algorithm

Claims (7)

An apparatus for processing an image representation variable length codeword data stream, comprising: Means (12) for generating data packets including short data packets comprising a prescribed number of words in response to the variable length codeword data stream; Data processing means (15) for delivering the data packets to an output; Means (76, 17) included in the data processing means, for generating fixed length data packets having the prescribed number of words, wherein a defined codeword can appear; And said means (76, FIG. 17) for filling the short data packets with no-operation null words necessary to define a packet boundary. The method of claim 1, And said data processing means conveys a sequence of data packets and packet headers to said output and comprises data selecting means (76) for filling said short packets with said null words. The method of claim 1, The data processing means, An input header buffer 70 for receiving headers containing information related to the contents of the associated data packet; An input data buffer 72 for receiving the data packets: An output buffer 78 for receiving a controlled sequence of headers and data packets, respectively, from the header buffer and the data buffer, And said data processing means comprising said data buffer, said header buffer and said output buffer exhibits uninterrupted operation for the reception and processing of said headers and data packets. The method of claim 3, wherein And said null words are provided in said short data packets following said data and header buffers. The method of claim 1, And the codewords are associated with a group of picture data and comprise a picture start codeword appearing at an inter-packet boundary. The method of claim 5, And the data stream comprises MPEG codewords including the picture start codeword. The method of claim 5, And a picture start codeword is associated with intraframe coded I-frame image data.