Transmission of high rate isochronous data in MPEG-2 data streams

• US 5,598,415 A
• Filed: 08/04/1995
• Issued: 01/28/1997
• Est. Priority Date: 08/04/1995
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Moroney, Paul, Nuber, Ray
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US08/511,266
• Time in Patent Office: 543 Days
• Field of Search: 370/84, 370/118, 370/94.1-94.3, 370/110.1, 370/100.1, 370/105.1, 370/112, 348/465, 348/464, 348/467, 375/354
• US Class Current: 370/474
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04N 19/895 in combination with error concealment
• CPC Class Codes: H04N 21/23614 Multiplexing of additional data and video streams arrangements for simultaneous broadcast of plural pieces of information H04H20/28
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/43072 of multiple content streams on the same device
• CPC Class Codes: H04N 21/4348 Demultiplexing of additional data and video streams
• CPC Class Codes: H04N 7/52 Systems for transmission of a pulse code modulated video signal with one or more other pulse code modulated signals, e.g. an audio signal or a synchronizing signal assembling of a multiplex stream by combining a video stream with other content or additional data, remultiplexing of multiplex streams, insertion of stuffing bits into the multiplex stream, assembling of a packetised elementary stream at server side H04N21/236; disassembling of a multiplex stream, remultiplexing of multiplex streams, extraction or processing of Service Information, disassembling of packetised elementary stream at client side H04N21/434
• CPC Class Codes: H04N 7/54 the signals being synchronous H04N21/23602, H04N21/23614, H04N21/2365, H04N21/2368, H04N21/4341, H04N21/4342, H04N21/4347, H04N21/4348 take precedence
• CPC Class Codes: H04N 7/56 Synchronising systems therefor

Abstract

A scheme is provided for communicating high rate isochronous data in an MPEG-2 type transport stream in a robust manner. The syntax for the data bitstream also provides for the communication of a data clock increment value to a decoder. The increment value enables a simplified and cost effective approach to the direct digital synthesis of a clock frequency necessary to recover data from the packetized data stream at the decoder. The time resolution for presenting isochronous data presentation units at the decoder is increased by providing a presentation time stamp (PTS) extension to supplement a standard MPEG-2 PTS.

Claims

1. A method for the robust transmission of high rate isochronous data in an MPEG-2 type transport stream, comprising the steps of:

providing said isochronous data in a packetized elementary stream (PES) having a PES header preceding a PES payload, said PES payload including an isochronous data header followed by a plurality of isochronous data presentation units;

aligning said isochronous data header and the presentation units which follow within said PES such that the first byte of the isochronous data header immediately follows the last byte of the PES header;

inserting a clock increment value in said isochronous data header specifying the ratio of said isochronous data rate to a reference clock rate, said clock increment value enabling said isochronous data rate to be derived from said reference clock rate at a decoder; and

packaging said PES into a plurality of isochronous data transport packets such that a first payload byte of each transport packet is the first byte of an isochronous data presentation unit and a last payload byte of each of said packets is the last byte of an isochronous data presentation unit.

2. A method in accordance with claim 1 comprising the further step of:

providing a presentation time-stamp (PTS) extension in said isochronous data header to supplement a standard MPEG-2 PTS provided in said PES header, the combination of said PTS extension with the standard PTS enabling the time resolution for presenting isochronous data presentation units at said decoder to be increased.

3. A method in accordance with claim 2 wherein said PTS extension is provided at the beginning of said isochronous data header.

4. A method in accordance with claim 3 wherein said PTS extension is an eight bit extension derived from the eight most significant bits of the standard MPEG-2 nine bit PCR extension.

5. A method in accordance with claim 4 wherein said eight bit PTS extension is combined with a standard 33-bit PTS to increase said time resolution from about 11.1 microseconds to about 74 nanoseconds.

6. A method in accordance with claim 5 wherein said isochronous data presentation units are each sixteen bits in length.

7. A method in accordance with claim 1 wherein said isochronous data presentation units are each sixteen bits in length.

8. A method for recovering isochronous data transmitted in accordance with the method of claim 1 comprising the steps of:

locating a PES header and an isochronous data header in a received data stream of said isochronous data transport packets;

extracting program clock reference (PCR) values from said isochronous data transport packets;

using said PCR values to recover said reference clock rate;

extracting said clock increment value from said isochronous data header;

using said extracted increment value to derive said isochronous data rate from said reference clock rate; and

recovering said isochronous data at said isochronous data rate.

9. A method in accordance with claim 8 wherein prior to transmission of said high rate isochronous data in said MPEG-2 type transport stream, a presentation time-stamp (PTS) extension is provided in said isochronous data header to supplement a standard MPEG-2 PTS provided in said PES header, the combination of said PTS extension with the standard PTS enabling the time resolution for presenting isochronous data presentation units at said decoder to be increased, said method for recovering the isochronous data comprising the further steps of:

extracting said standard PTS from said PES header;

extracting said PTS extension from said isochronous data header; and

using the extracted standard PTS and PTS extension to determine a correct time for commencing the presentation of the isochronous data presentation units contained in said received data stream.

10. A method in accordance with claim 9 wherein said PTS extension is provided at the beginning of said isochronous data header.

11. A method in accordance with claim 10 wherein said PTS extension is derived from the eight most significant bits of the standard MPEG-2 nine bit PCR extension.

12. A method in accordance with claim 11 wherein said isochronous data presentation units are each sixteen bits in length.

13. A method in accordance with claim 1 comprising the further step of inserting PCR values into said isochronous data transport packets for use by said decoder in recovering said reference clock rate.

14. Apparatus for recovering isochronous data carried at an isochronous data rate in an MPEG-2 type transport stream comprising:

means for locating a packetized elementary stream (PES) header and an isochronous data header in a received isochronous data transport packet stream;

means for extracting program clock reference (PCR) values from said isochronous data transport packet stream;

means responsive to said PCR values for recovering a reference clock rate;

means for extracting a clock increment value from said isochronous data header;

means for processing said extracted clock increment value and the recovered reference clock rate to reproduce said isochronous data rate; and

means responsive to the isochronous data rate reproduced by said processing means for recovering said isochronous data.

15. Apparatus in accordance with claim 14 further comprising:

means for extracting a presentation time-stamp (PTS) for the isochronous data from said PES header;

means for extracting a PTS extension for the isochronous data from said isochronous data header; and

means responsive to said extracted PTS and PTS extension for determining a correct time for commencing the presentation of isochronous data presentation units contained in said received data transport packet stream.

16. Apparatus in accordance with claim 15 wherein said PTS extension is extracted from the beginning of said isochronous data header.

17. Apparatus in accordance with claim 15 wherein said isochronous data presentation units are each sixteen bits in length.

18. Decoder apparatus for recovering information data from a data stream, said information being transmitted in said data stream at an information data rate, comprising:

a direct digital synthesis (DDS) clock for providing a plurality of reference clock rates based on a system clock frequency;

means for locating an information data header in a received information data transport packet stream; and

means for extracting a clock increment value from said information data header, said clock increment value specifying the ratio of said information data rate to said system clock frequency;

wherein said DDS clock is responsive to said clock increment value for providing a clock signal at said information data rate for use in outputting said information data.

19. Apparatus in accordance with claim 18 wherein said increment value is an integer.

20. Apparatus in accordance with claim 19 wherein:

said data stream is an MPEG-2 type transport stream;

said system clock frequency is about 27 MHz; and

said increment value is the nearest integer to the product of the information data rate and a modulus value N divided by 27,000,000.

21. Apparatus in accordance with claim 20 wherein said modulus value N=536,868,000.

22. Apparatus in accordance with claim 18 wherein:

said system clock frequency has a range of tolerance enabling said DDS clock to generate a substantially continuous range of reference clock rates from a system clock to recover information at any information rate within said substantially continuous range.