Data word indicator in a system for assembling transport data packets

• US 5,796,743 A
• Filed: 05/23/1996
• Issued: 08/18/1998
• Est. Priority Date: 11/30/1993
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Brooks, Charles Alan, Acampora, Alfonse Anthony, Bunting, Richard Michael, Harris, David Isaac
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): VANDERPUYE, KENNETH N
• Application Number:
  US08/649,634
• Time in Patent Office: 817 Days
• Field of Search: 370/470, 370/471, 370/473, 370/474, 370/466, 370/381, 370/384, 370/428, 370/395, 348/384, 348/469, 348/426, 348/474, 348/409
• US Class Current: 370/474
• CPC Class Codes: H04N 21/236 Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream multiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00

Abstract

In a digital television signal processing system, a special codeword, a Packet Alignment Flag (PAF), is inserted into an MPEG codeword bitstream to signify the presence of a Group of Pictures (GOP). The PAF immediately precedes a Picture Start codeword for an "I" frame, which initiates a GOP. A data packet under construction when a PAF appears is terminated since a GOP is intended to begin at a packet boundary. Such termination may result in an abbreviated packet of MPEG codewords less than a prescribed number of bits needed to complete a data packet. The last word of each packet is designated as such to facilitate the subsequent combining of data packets with respective headers. An incomplete data packet is filled with null (zeroed bits) words to make up a complete data packet with a prescribed number of bits.

Claims

1. Apparatus for processing an image representative datastream, comprising:

means (14) for providing a datastream including a succession of Groups of Pictures;

first processing means (12) for forming variable length datastream data words into fixed length data packets, said data packets subject to containing an unpredictable variable number of data words;

means (12,37 (FIG. 2c);

46 (FIG.

     4)) for providing a Last Word indicator designating a last one of said unpredictable number of data words in a data packet; and

second processing means (15) responsive to said data packets and to said Last Word indicator for producing output packed data transport packets.

2. Apparatus according to claim 1, wherein

said Last Word indicator is associated with a packet boundary.

3. Apparatus according to claim 1, and further including

means (15,76 (FIG. 17)) for filling SHORT data packets with no-operation null words as needed in response to said Last Word indicator so that said packed data transport packets exhibit a prescribed number of words.

4. Apparatus according to claim 1, wherein

a Picture Start codeword is associated with each said Group of Pictures;

and

said Last Word indicator is associated with a data packet preceding said Picture Start codeword.

5. Apparatus according to claim 4, wherein

said datastream comprises MPEG codewords including said Picture Start codeword.

6. Apparatus according to claim 1, wherein

said second processing means (15) includes means (78 (FIG. 17))for combining data packets with a header to form each said transport packet.

7. Apparatus for processing an image representative MPEG compatible datastream including a Group of Pictures and a Picture Start codeword associated with each said Group of Pictures;

said apparatus comprising;

first processing means responsive to said datastream for forming variable length datastream data words into fixed length data packets, said data packets subject to containing an unpredictable variable number of data words;

means for providing a Last Word indicator associated with a last one of said unpredictable number of data words in a data packet preceding a Picture Start codeword; and

second processing means responsive to said data packets and to said Last Word indicator for producing output packed data transport packets.

8. Apparatus according to claim 7 and further comprising:

a forward error correction (FEC) network for processing said output packets.