Multiplex communications – Communication techniques for information carried in plural... – Assembly or disassembly of messages having address headers
Patent
1996-05-23
1998-08-18
Safourek, Benedict V.
Multiplex communications
Communication techniques for information carried in plural...
Assembly or disassembly of messages having address headers
348384, H04N 712
Patent
active
057967431
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is related to the field of digital signal processing, and more particularly to method and apparatus for assembling transport packets such as may be used for conveying coded MPEG-like data in a high definition television system, for example.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,168,356-Acampora et al. describes a system for processing a high definition television (HDTV) signal subjected to MPEG-like variable length coding. MPEG is a standardized coding format being established by the International Organization for Standardization. The standard is described in the document "International Organization for Standardization," ISO/IEC DIS 11172, Coding for Moving Pictures and Associated Audio for Digital Storage Media, Rev. Nov. 23, 1991 which document is incorporated herein by reference for description of the general code format. In the Acampora et al. system, codewords are prioritized to reflect high priority and low priority information in a datastream. The codeword datastream is passed to a transport processor which packs the codeword data into transport cells each including header and packed data payload sections, and which provides output high priority and low priority datastreams.
A major function of the transport processor is to pack variable length codeword data, issued by a preceding priority processor, into packed data words. An accumulation of packed words, called a data packet, is prefaced with a transport header.
The transport packet format enhances resynchronization and signal recovery at a receiver, e.g., after a signal disruption due to a transmission channel disturbance, by providing header data from which a receiver can determine re-entry points into the data stream on the occurrence of a loss or corruption of transmitted data. Synchronization of data at an MPEG decoder also is facilitated by a Group of Pictures (GOP) beginning at a packet boundary. As will be seen, a GOP is a series of one or more pictures, or frames, intended to assist random access into a coded video bitstream sequence. Resynchronization is also facilitated by responding to an intracoded I-frame picture start codeword, and by placing the picture start codeword at a packet boundary, e.g., in a system according to the MPEG standard. Apparatus in accordance with the principles of the present invention facilitates the development of a transport packet.
SUMMARY OF THE INVENTION
Apparatus in accordance with the principles of the present invention is responsive to an image representative codeword datastream comprising MPEG codewords including a sequence of groups of pictures. A codeword processor forms words into data fixed length packets, which may contain an unpredictable variable number of variable length words. A Last Word Indicator designates the last data word in a packet as such to facilitate the subsequent combining of data packets with associated headers.
In accordance with a feature of the invention, an abbreviated data packet is filled with null (zeroed bits) words as needd to make up a complete data packet with a prescribed number of words.
BRIEF DESCRIPTION OF THE DRAWING
In the drawings:
FIG. 1 is a block diagram of a portion of a video signal encoder including data word controller, data packer and data/header combiner apparatus according to the present invention.
FIGS. 2A, 2B and 2C show details of a word controller and data packer of FIG. 1.
FIG. 3 is a truth table associated with the operation of a word status controller shown in FIG. 2A.
FIG. 4 shows details of a packed data assembler network.
FIGS. 5-16 depict examples of last word generation.
FIG. 17 shows details of a data and header combiner unit shown in FIG. 1.
FIG. 18 is a state diagram associated with the operation of a state controller shown in FIG. 17.
FIG. 19 is a block diagram of an HDTV encoding system including apparatus according to the present invention.
FIGS. 20A and 20B are pictorial representations of sequences of image fields/frames of encoded video signals.
FIG. 21 is a pictorial represent
REFERENCES:
patent: 4160877 (1979-07-01), Vander Mey
patent: 4704606 (1987-11-01), Hasley
patent: 4736369 (1988-04-01), Barzilai et al.
patent: 5168356 (1992-12-01), Acampora et al.
patent: 5287178 (1994-02-01), Acampora et al.
patent: 5371547 (1994-12-01), Siracusa et al.
patent: 5384770 (1995-01-01), Mays et al.
patent: 5535221 (1996-07-01), Hijikata et al.
Acampora Alfonse Anthony
Brooks Charles Alan
Bunting Richard Michael
Harris David Isaac
General Electric Company
Herrmann Eric P.
Kurdyla Ronald H.
Safourek Benedict V.
Tripoli Joseph S.
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