Exploitation of null packets in packetized digital television systems

• US 7,376,159 B1
• Filed: 01/03/2002
• Issued: 05/20/2008
• Est. Priority Date: 01/03/2002
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Basse, Hanno, Michener, James A., Stanger, Leon J., Plummer, Robert H., Newman, Richard K.
• Primary Examiner(s): Jung; Min
• Application Number:
  US10/038,174
• Time in Patent Office: 2,329 Days
• Field of Search: 370/537, 370/538, 370/540, 370/528
• US Class Current: 370/528
• CPC Class Codes: H04J 3/1682 Allocation of channels according to the instantaneous demands of the users, e.g. concentrated multiplexers, statistical multiplexers
• CPC Class Codes: H04N 21/23611 Insertion of stuffing data into a multiplex stream, e.g. to obtain a constant bitrate synchronisation arrangements in time-division multiplex systems using bit stuffing for systems with different or fluctuating information rates H04J3/073
• 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 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/23655 Statistical multiplexing, e.g. by controlling the encoder to alter its bitrate to optimize the bandwidth utilization
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams
• CPC Class Codes: H04N 21/4348 Demultiplexing of additional data and video streams

Abstract

A system and method for adding auxiliary data D_A to an output data stream from a statistical multiplexer is disclosed. An auxiliary multiplexer accepts a statistically multiplexed data stream, and substitutes auxiliary data packets for null data packets. The auxiliary multiplexer controls the number of null packets in the statistically multiplexed data stream by controlling the target bandwidth B_T of the statistical multiplexer, or by modifying the statistical multiplexer equation to make the auxiliary data stream a participant in the negotiation process of allocating throughput among the data sources.

Claims

1. An apparatus for adding auxiliary data D_A to an output data stream, comprising:

a statistical multiplexer having a plurality of inputs including a first input, and an output providing the output data stream;

a first encoder, having an output communicatively coupled to the a first statistical multiplexer input, the first encoder for compressing a first data stream D₁ according to a first actual data rate BW_A1 that is less than or equal to a first granted data rate BW_G1 granted by the statistical multiplexer in response to a requested data rate BW_R1 from the encoder, the difference between the first actual data rate BW_A1 and the first granted data rate BW_G1 defining an encoder overhead rate BW_OE1 such that BW_G1−

BW_A1=BW_OE1≧

0, the first encoder having an output including a compressed version of the first data stream d₁ provided at the actual data rate BW_A1 and encoder null data N_E1 at the overhead rate BW_OE1; and

an auxiliary multiplexer, communicatively coupled to the statistical multiplexer, for sensing encoder null data N_E and for substituting at least a portion of the auxiliary data D_A for the encoder null data N_H.

15. The apparatus of claim 1, wherein the auxiliary multiplexer is communicatively coupled to the output of the encoder and the input of the statistical multiplexer to sense the encoder null data N_E.

2. The apparatus of clam 1, wherein the auxiliary multiplexer is communicatively coupled to the output of the statistical multiplexer.

3. The apparatus of claim 2, further comprising a buffer, communicatively coupled to the auxiliary multiplexer, the buffer for buffering the auxiliary data.

4. The apparatus of claim 3, wherein the auxiliary multiplexer substitutes the auxiliary data according to an unused memory of the buffer.

5. The apparatus of claim 2, wherein the auxiliary multiplexer further senses statistical multiplexer null data N_SM and substitutes at least a portion of the auxiliary data for the multiplexer null data N_SM.

6. The apparatus of claim 2, wherein:

the statistical multiplexer manages the the first encoder output according to a first command input describing a target data rare of the output data stream B_T; and

the auxiliary multiplexer is communicatively coupled to the statistical multiplexer first input to command a change the target data rate of the output data stream B_T.

7. The apparatus of claim 6, further comprising a buffer, communicatively coupled to the auxiliary multiplexer, the buffer for buffering the auxiliary data, wherein the auxiliary multiplexer changes the target data rare according to an unused memory of the buffer.

8. The apparatus of claim 6, wherein the auxiliary multiplexer changes the target data rate according to one or more auxiliary data parameters selected from the group comprising:

a minimum auxiliary data rate BW_MIN;

a maximum auxiliary data rare BW_MAX;

a nominal auxiliary data rate BW_AVG measured over a time period t_per; and

a priority.

9. The apparatus of claim 6, wherein the change in the target data rate of the output data is commanded to decrease the target rate of the output data stream B_T to permit the substitution of auxiliary data D_A for the multiplexer null data N_SM.

10. The apparatus of claim 6, wherein:

the auxiliary multiplexer further senses statistical multiplexer null data N_SM and substitutes at least a portion of the auxiliary data for the multiplexer null data N_SM; and

the change in the target data rate of the output data is commanded to decrease the target rate of the output data stream B_T to permit the substitution of auxiliary data D_A for data selected from the group comprising the encoder null data N_E1 and the multiplexer null data N_SM.

11. The apparatus of claim 10, wherein the auxiliary data is added at a pre-specified minimum auxiliary data rate.

12. The apparatus of claim 2, further comprising:

a second encoder, having an output communicatively coupled to the a first statistical multiplexer input, the second encoder for compressing a second data stream D₂ according to a second actual data rate BW_A2 that is less than or equal to a second granted data rate BW_G2 granted by the statistical multiplexer [in response to a requested data rate BW_R1 from the second encoder, the difference between the second actual data rate BW_A2 and the first granted data rate BW_G2 defining an encoder overhead rate BW_OE2 such that BW_G1−

BW_A1=BW_OE2≧

0, the second encoder having an output including an compressed version of the second data stream provided at the actual data rate BW_A2 and encoder null data N_E2 at the overhead rate BW_OE2, the second encoder having an output;

wherein the statistical multiplexer allocates data presented at the plurality of inputs to the statistical multiplexer output according to a statistical multiplexer second command input; and

wherein the auxiliary multiplexer is communicatively coupled to the statistical multiplexer second input to command a change in the allocation of the data presented at the plurality of inputs to the statistical multiplexer output.

13. The apparatus of claim 12, wherein the auxiliary multiplexer changes the allocation of the data presented at the plurality of inputs to the statistical multiplexer output according to an unused memory of a buffer communicatively coupled to the auxiliary multiplexer, the buffer for buffering the auxiliary data.

14. The apparatus of claim 13, wherein the multiplexer changes the allocation of the data presented at the plurality of inputs to the statistical multiplexer output according to an unused memory of the buffer.

16. A method of adding auxiliary data D_A to a data stream, comprising the steps of:

accepting a statistically multiplexed data stream having null data;

substituting at least a portion of the auxiliary data D_A for the null data in the statistically multiplexed data stream; and

prior to the substitution of the at least a portion of the auxiliary data D_A for the null data in the statistically multiplexed data stream, controlling an amount of the null data in the statistically multiplexed data stream to provide sufficient null data to permit the substitution of at least some of the auxiliary data D_A in the statistically multiplexed data stream.

17. The method of claim 16, wherein the auxiliary data D_A is non-opportunistic data.

18. The method of claim 16, further comprising the step of:

buffering the auxiliary data D_A until there is sufficient null data to permit the substitution of the at least some of the auxiliary data D_A in the statistically multiplexed data stream.

19. The method of claim 18, wherein the amount of null data is controlled according to a relationship between an amount of the buffered auxiliary data D_A and a capacity of a buffer scoring the buffered data.

20. The method of claim 16, wherein the null data comprises statistical multiplexer null data N_SM.

21. The method of claim 20, wherein the statistically multiplexed data stream is statistically multiplexed to a throughput less than or equal to a target throughput value BW_T, and the step of controlling an amount of null data in the statistically multiplexed data stream comprises the step of altering the target throughput value BW_T.

22. The method of claim 16, wherein the null data comprises encoder null data N_E.

23. The method of claim 22, wherein the statistically multiplexed data stream is statistically multiplexed according to a statistical multiplexer equation, and the step of controlling an amount of null data in the statistically multiplexed data stream comprises the step of altering the statistical multiplexer equation.

24. The method of claim 16, further comprising the step of:

examining the auxiliary data D_A for non-essential data; and

eliminating the non-essential data from the auxiliary data D_A before substituting the auxiliary data D_A for the null data in the statistically multiplexed data stream.

25. The method of claim 16, wherein the amount of null data in the statistically multiplexed data stream is controlled according to a parameter set describing the auxiliary data D_A, including:

a minimum throughput required to keep the data service active BW_MIN;

a maximum sustained throughput of the data service BW_MAX; and

a nominal or guaranteed rate over a time period BW_AVG.

26. The method of claim 16, wherein the data stream comprises a set of data packets all having a packer ID including a first data packet and a second data packet temporally adjacent the first data packet, and the step of substituting at least a portion of the auxiliary data D_A for the null data in the statistically multiplexed data stream comprises the steps of:

substituting at least a portion of the auxiliary data D_A for the data in the second data packet if the first data packet includes at least a number NB consecutive zero data values and the second data packer includes all zero data values.

27. A system for transmitting auxiliary data D_A packetized satellite signal, comprising:

a statistical multiplexer having a plurality of inputs including a first input, and an output providing an output data stream;

a first encoder, having an output communicatively coupled to the a first statistical multiplexer input, the first encoder for compressing a first data stream D₁ according to a first actual data race BW_A1 that is less than or equal to a first granted data rate BW_G1 granted by the statistical multiplexer in response to a requested data rate BW_R1 from the encoder, the difference between the first actual data rate BW_A1 and the first granted data rate BW_G1 defining an encoder overhead rate BW_OE1 such that BW_G1−

BW_A1=BW_OE1≧

0, the first encoder having an output including an compressed version of the first data stream d₁ provided at the actual data rate BW_A1 and encoder null data N_E1 at the overhead rate BW_OE; and

an auxiliary multiplexer, communicatively coupled to the statistical multiplexer, for sensing encoder null data NF and for substituting at least a portion of the auxiliary data D_A for the encoder null data N_B;

a modulator communicatively coupled to the auxiliary multiplexer, for modulating the output data stream;

a transmitter, communicatively coupled to the modulator for transmitting the output data stream; and

a transponder, for receiving the transmitted modulated output data stream and for retransmitting the received output data stream to a subscriber.

28. The system of claim 27, wherein the auxiliary multiplexer is communicatively coupled to the output of the encoder and the input of the statistical multiplexer to sense the encoder null data.