Bandwidth optimization of video program bearing transport streams

• US 20050105486A1
• Filed: 12/09/2004
• Published: 05/19/2005
• Est. Priority Date: 01/14/1998
• Status: Active Grant

• Current Assignee: TANDBERG Television, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: TANDBERG Television, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Robinett, Robert, Gratacap, Regis
• Granted Patent: US 7,620,073 B2
• Time in Patent Office: Days
• US Class Current: 370/321
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/63345 by transmitting keys key distribution for secret or secure communication H04L9/08; network support of key management H04L63/06
• CPC Class Codes: H04N 21/8547 involving timestamps for synchronizing content

Abstract

A method and system are provided for remultiplexing program bearing data. The remultiplexing method and system are applicable to MPEG-2 compliant transport streams carrying video programs. A descriptor based system is used for scheduling the timely output of transport packets wherein each descriptor records a dispatch time as well as a receipt time for each transport packet. The receipt time is used for estimating program clock reference adjustments, but final program clock reference adjustment is performed in hardware in relation to the precise output timing of each transport packets. A descriptor and transport packet caching technique is used for decoupling the synchronous receipt and transmission of transport packets from any asynchronous processing performed thereon. The descriptors can also be used for managing scrambling and descrambling control words (encryption and decryption keys). Remultiplexing functions may be distributed across a network. The remultiplexer can furthermore optimize the bandwidth of transport streams by replacing null transport packets with transport packet data to be inserted into the output transport stream. Program data transmitted via asynchronous communication links is re-timed and assistance is provided for outputting program data on such asynchronous communication links to reduce a variation in end-to-end delay incurred by the program data. Remultiplexing and program specific information can be seamlessly dynamically varied without stopping, or introducing a discontinuity in, the flow of outputted transport packets. A technique is also provided for locking multiple internal reference clock generators.

Claims

1. A method for optimizing the bandwidth of a transport stream comprising the steps of:

(a) receiving a transport stream at a predetermined bit rate, said transport stream including variably compressed program data bearing transport packets and one or more null transport packets, each of said null transport packets being inserted into a time slot of said received transport stream to maintain said predetermined bit rate of said transport stream when none of said compressed program data bearing transport packets are available for insertion into said received transport stream at said transport packet time slot, and

(b) selectively replacing one or more of said null transport packets with another to-be-remultiplexed data bearing transport packet.

2. The method of claim 1 wherein said another to-be-remultiplexed data bearing transport packet contains program specific information.

3. The method of claim 1 wherein said another to-be-remultiplexed data bearing transport packet contains transactional data having no bit rate or transmission latency requirement for presenting information in a continuous fashion.

4. The method of claim 1 further comprising the steps of:

(c) extracting selected ones of said transport packets of said received transport stream and discarding each non-selected transport packet, each of said null transport packets being discarded,

(d) storing said selected transport packets,

(e) storing at least one other data bearing transport packet,

(f) scheduling each of said stored transport packets for output in an outputted transport stream, and

(g) outputting each of said stored transport packets in a time slot corresponding to said schedule.

5. The method of claim 4 further comprising the steps of:

(h) at each time slot of said outputted transport stream for which a corresponding one of said stored transport packets is scheduled, outputting said corresponding stored transport packet scheduled for said time slot, and

(i) if no transport packet is scheduled for output at one of said time slots, outputting a null transport packet,

wherein said null transport packets of said outputted transport stream occupy less bandwidth of said outputted transport stream than said null transport packets occupy in each transport stream received in step (a).

6. The method of claim 3 wherein said step (b) further comprises selectively assigning data bearing transport packets to time slots of said outputted transport stream so as to regulate a transmission bit rate of said data bearing transport packets to a receiver buffer.

7. A remultiplexer for optimizing the bandwidth of a transport stream comprising:

a first interface for receiving a transport stream at a predetermined bit rate, said transport stream including variably compressed program data bearing transport packets and one or more null transport packets, each of said null transport packets being inserted into a time slot of said received transport stream to maintain said predetermined bit rate of said transport stream when none of said compressed program data bearing transport packets are available for insertion into said received transport stream at said transport packet time slot, and

a processor for selectively replacing one or more of said null transport packets with another to-be-remultiplexed data bearing transport packet.

8. The remultiplexer of claim 7 wherein said another to-be-remultiplexed data bearing transport packet contains program specific information.

9. The remultiplexer of claim 7 wherein said another to-be-remultiplexed data bearing transport packet contains transactional data having no bit rate or transmission latency requirement for presenting information in a continuous fashion.

10. The remultiplexer of claim 7 wherein said first interface and said processor extract selected ones of said transport packets of said received transport stream and discard each non-selected transport packet, each of said null transport packets being discarded, said remultiplexer further comprising:

a memory in which said first interface and said processor store said selected transport packets, and in which said processor stores at least one other data bearing transport packet, said processor scheduling each of said stored transport packets for output in an outputted transport stream, and

a second interface for outputting each of said stored transport packets in a time slot corresponding to said schedule.

11. The remultiplexer of claim 10 wherein, at each time slot of said outputted transport stream for which a corresponding one of said stored transport packets is scheduled, said second interface outputs said corresponding stored transport packet scheduled for said time slot, and, if no transport packet is scheduled for output at one of said time slots, said second interface outputs a null transport packet, said null transport packets of said outputted transport stream occupying less bandwidth of said outputted transport stream than said null transport packets occupy in each received transport stream.

12. The remultiplexer of claim 9 wherein said processor selectively assigns data bearing transport packets to time slots of said outputted transport stream so as to regulate a transmission bit rate of said data bearing transport packets to a receiver buffer.

13. A bandwidth optimized transport stream produced by the steps of:

(a) receiving a transport stream at a predetermined bit rate, said transport stream including variably compressed program data bearing transport packets and one or more null transport packets, each of said null transport packets being inserted into a time slot of said received transport stream to maintain said predetermined bit rate of said transport stream when none of said compressed program data bearing transport packets are available for insertion into said received transport stream at said transport packet time slot, and

(b) selectively replacing one or more of said null transport packets with another to-be-remultiplexed data bearing transport packet.

14. The bandwidth optimized bitstream of claim 13 produced by the further steps of:

(c) extracting selected ones of said transport packets of said received transport stream and discarding each non-selected transport packet, each of said null transport packets being discarded,

(d) storing said selected transport packets,

(e) storing at least one other data bearing transport packet,

(f) scheduling each of said stored transport packets for output in an outputted transport stream, and

(g) outputting each of said stored transport packets in a time slot corresponding to said schedule.

15. The bandwidth optimized transport stream of claim 14 produced by the further steps of:

(h) at each time slot of said outputted transport stream for which a corresponding one of said stored transport packets is scheduled, outputting said corresponding stored transport packet scheduled for said time slot, and

(i) if no transport packet is scheduled for output at one of said time slots, outputting a null transport packet,

wherein said null transport packets of said outputted transport stream occupy less bandwidth of said outputted transport stream than said null transport packets occupy in each transport stream received in step (a).

16. The bandwidth optimized transport stream of claim 13 wherein said step (b) further comprises the step of selectively assigning data bearing transport packets to time slots of said outputted transport stream so as to regulate a transmission bit rate of said data bearing transport packets to a receiver buffer.