Receipts and dispatch timing of transport packets in a video program bearing stream remultiplexer

• US 6,292,490 B1
• Filed: 01/14/1998
• Issued: 09/18/2001
• Est. Priority Date: 01/14/1998
• Status: Expired due to Term

• Current Assignee: Skystream Networks Incorporated (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Skystream Corporation
• Inventors: Slattery, William, Gratacap, Regis
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Elallam, Ahmed
• Application Number:
  US09/007,212
• Time in Patent Office: 1,343 Days
• Field of Search: 370/358, 370/360, 370/378, 370/379, 370/381, 370/382, 370/389, 370/394, 370/395, 370/400, 370/412, 370/420, 370/428, 370/429, 370/458, 370/468, 370/473, 370/475, 370/477, 370/503, 370/508, 370/535, 370/538
• US Class Current: 370/412
• 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 remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said method comprising the steps of:

(a) receiving a transport packet from a particular input port,

(b) allocating an unused descriptor to said received transport packet,

(c) recording a receipt time stamp in said allocated descriptor indicating a time at which said transport packet was received, and

(d) scheduling transmission of said received transport packet according to said receipt time stamp and an internal buffering delay between receipt of said transport packet and output of said transport packet,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

2. A method for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said method comprising the steps of:

(a) receiving a transport packet from a particular input port,

(b) allocating an unused descriptor to said received transport packet,

(c) recording a receipt time stamp in said allocated descriptor indicating a time at which said transport packet was received,

(d) examining each descriptor in said receipt queue,

(e) allocating a descriptor of a transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any

(g) assigning a dispatch time to said allocated descriptor of said transmit queue, and

(h) ordering said descriptors of said transmit queue in order of increasing dispatch time,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

3. The method of claim 2 further comprising the steps of:

(i) transmitting each transport packet, to which a corresponding descriptor in said transmit queue points, from said output port in a time slot of an outputted transport stream corresponding to said dispatch time assigned to said corresponding descriptor.

4. A method for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said method comprising the steps of:

(a) sequentially retrieving each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points, and

(b) at a time corresponding to a dispatch time recorded in each retrieved descriptor, transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved descriptor,

wherein said descriptor containing said dispatch time is a separate data structure not transmitted with said retrieved transport packet.

5. A method for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said method comprising the steps of:

(a) sequentially retrieving each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points,

(b) at a time corresponding to a dispatch time recorded in each retrieved descriptor, transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved,

(c) examining each descriptor in one or more queues of descriptors pointing to to-be-outputted transport packets,

(d) allocating a descriptor of said transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any

(e) assigning a dispatch time to said allocated descriptor of said transmit queue, and

(f) ordering said descriptors of said transmit queue in order of increasing dispatch time.

6. A remultiplexer for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized and remultiplexer comprising:

a cache,

a data link control circuit connected to said cache for receiving a transport packet from a particular input port, for allocating an unused descriptor of said cache to said received time at which said transport packet was received, and

a processor for scheduling transmission of said received transport packet according to said receipt time stamp and an internal buffering delay between receipt of said transport packet and output of said transport packet,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

7. A remultiplexer for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized and remultiplexer comprising:

a cache,

a data link control circuit connected to said cache for receiving a transport packet from a particular input port, for allocating an unused descriptor of said cache to said received time at which said transport packet was received, and

a processor for examining each descriptor in said receipt queue, for allocating a descriptor of a transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any, for assigning a dispatch time to said allocated descriptor of said transmit queue, and for ordering said descriptors of said transmit queue in order of increasing dispatch time,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

8. The method of claim 7 further comprising:

a second data link control circuit for transmitting each transport packet, to which a corresponding descriptor in said transmit queue points, from said output port in a time slot of an outputted transport stream corresponding to said dispatch time assigned to said corresponding descriptor.

9. A remultiplexer for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said remultiplexer comprising:

a cache, and

a data link control circuit connected to said cache for sequentially retrieving from said cache each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points, and, at a time corresponding to a dispatch time recorded in each retrieved descriptor, for transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved descriptor,

wherein said descriptor containing said dispatch time is a separate data structure not transmitted with said retrieved transport packet.

10. A remultiplexer for remultiplexing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said remultiplexer comprising:

a cache,

a data link control circuit connected to said cache for sequentially retrieving from said cache each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points, and, at a time corresponding to a dispatch time recorded in each retrieved descriptor, for transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved descriptor;

a processor for examining each descriptor in one or more queues of descriptors pointing to to-be-outputted transport packets, for allocating a descriptor of said transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any, for assigning a dispatch time to said allocated descriptor of said transmit queue, and for ordering said description of said transmit queue in order of increasing dispatch time.

11. A transport stream containing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said transport stream being produced by the steps of:

(a) sequentially retrieving each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points, and

(b) at a time corresponding to a dispatch time recorded in each retrieved descriptor, transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved descriptor,

wherein said descriptor containing said dispatch time is a separate data structure not transmitted with said retrieved transport packet.

12. A transport stream containing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said transport stream being produced by the steps of:

(a) receiving a transport packet from a particular input port,

(b) allocating an unused descriptor to said received transport packet,

(c) recording a receipt time stamp in said allocated descriptor indicating a time at which said transport packet was received, and

(d) scheduling transmission of said received transport packet according to said receipt time stamp and an internal buffering delay between receipt of said transport packet and output of said transport packet,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

13. A transport steam containing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said transport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said transport stream being produced by the steps of:

(a) receiving a transport packet from a particular input port,

(b) allocating an unused descriptor to said received transport packet,

(c) recording a receipt time stamp in said allocated descriptor indicating a time at which said transport packet was received,

(d) examining each descriptor in said receipt queue,

(e) allocating a descriptor of a transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any

(g) assigning a dispatch time to said allocated descriptor of said transmit queue, and

(h) ordering said descriptors of said transmit queue in order of increasing dispatch time,

wherein said allocated descriptors are maintained in a receipt queue associated with said input port in order of receipt from said particular input port.

14. The transport stream of claim 13 produced by the further steps of:

(i) transmitting each transport packet, to which a corresponding descriptor in said transmit queue points, from said output port in a time slot of an outputted transport stream corresponding to said dispatch time assigned to said corresponding descriptor.

15. A transport steam containing transport packets, including transport packets containing compressed data for one or more video programs, each of said video programs for which said sport packets contain compressed data comprising a constant end-to-end communication delay requirement, an independent bit rate and program clock reference time stamps of an independent encoder system time clock to which decoding and presentation of said video program is synchronized, said transport stream being produced by the steps of:

(a) sequentially retrieving each descriptor from a queue of transmit descriptors, and a transport packet to which each retrieved descriptor points,

(b) at a time corresponding to a dispatch time recorded in each retrieved descriptor, transmitting said retrieved transport packet to which said retrieved descriptor points in a time slot of an outputted transport stream corresponding to said dispatch time recorded in said retrieved,

(c) examining each descriptor in one or more queues of descriptors pointing to to-be-outputted transport packet,

(d) allocating a descriptor of said transmit queue associated with an output port from which a transport packet pointed to by each examined descriptor is to be transmitted, if any

(e) assigning a dispatch time to said allocated descriptor of said transmit queue, and

(f) ordering said descriptors of said transmit queue in order of increasing dispatch time.