Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-01-27
2001-10-30
Nguyen, Chau (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S389000, C370S474000, C348S423100
Reexamination Certificate
active
06310898
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to video and audio compression technology, and more particularly to an MPEG-2 transport stream multiplexer for combining program elementary video and audio streams consisting of one or more programs such that no processor-based copying is necessary and all data movement is performed by direct memory access (DMA).
Valid MPEG-2 Transport Streams are fully defined by the International Standard ISO/IEC 13818-1, Generic Coding of Moving Pictures and Associated Audio: Systems (11/94). An MPEG-2 Transport Stream has 188-byte Transport Stream (TS) packets. Each TS packet is identified by a particular 13-bit packet identifier (PID). Every audio and video elementary stream is uniquely identified by the PID used in the TS packets that contain them. Additional PIDs contain Program Specific Information (PSI) that includes a Program Association Table (PAT) and a Program Map Table (PMT) which describe the complete transport stream multiplex pattern. Such a multiplex pattern has one or more programs, each of which has one or more elementary streams. Each TS packet has a header and data. The header contains a sync byte, the packet's PID, a four-bit continuity counter together with other information. The elementary streams are encapsulated as Packetized Elementary Streams (PES) before being broken into the TS packets.
What is desired is a compressed video and audio transport stream multiplexer for combining elementary streams and program specific information without burdening a microprocessor with excessive copying.
BRIEF SUMMARY OF THE INVENTION
Accordingly the present invention provides a compressed video and audio transport stream multiplexer that reduces the burden on a microprocessor by pre-building a multiplex pattern in microprocessor local memory. The microprocessor has a DMA controller, and an assembly buffer is allocated in the local memory for DMA control blocks. Transport stream headers are generated as well as special headers for clock and stuffing. A null packet is provided and program specific tables are generated for the multiplex pattern. Packetized elementary streams from various sources are loaded into packetized elementary stream buffers. The DMA control blocks are filled in the assembly buffer and the data is transferred from the local memory according to the multiplex pattern to provide output transport stream packets.
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Lee, “An Interrgrate Transport Technique for Circuit and Packet Switched Trafic”, IEEE No. Conf. 7, pp. 110-118, Mar. 1988.
Gray Francis I.
Nguyen Chau
Tektronix Inc.
Tran Maikhanh
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