Combined jitter and multiplexing systems and methods

• US 7,529,276 B1
• Filed: 09/03/2002
• Issued: 05/05/2009
• Est. Priority Date: 09/03/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ramakrishnan, Sangeeta
• Primary Examiner(s): Ngo; Ricky
• Assistant Examiner(s): PATEL, CHANDRAHAS B
• Application Number:
  US10/235,371
• Time in Patent Office: 2,436 Days
• Field of Search: 370/412, 370/468, 370/516, 370/537
• US Class Current: 370/516
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/2368 Multiplexing of audio and video streams
• 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 21/4341 Demultiplexing of audio and video streams
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer

Abstract

Described herein are systems and methods for processing and transmitting data included in packets with jitter. The systems and methods combine a jitter buffer and a buffer scanned by a look ahead window as a combined buffer. The combined buffer varies look ahead window and performance of a process that uses the look ahead window based on the current jitter support in the buffer. More specifically, the flexible buffering techniques flexibly adapt the size of the look ahead window based on the amount of buffer space used for jitter support. When jitter support requirements are low, the size of the look ahead window is increased. When the look ahead window is implemented with a multiplexer, the multiplexer may benefit from a larger look ahead window and improve multiplexer performance. Improved multiplexer performance may lead to less or more intelligent re-encoding and bit rate reduction for video data transmission applications, leading to improved decoded output video quality.

Claims

1. A network device for transmitting compressed video data onto a channel, the network device comprising:

an input network interface designed or configured to receive multiple bitstreams, at least one of the multiple bitstreams having packets that include jitter and transport compressed video data;

a buffer designed or configured to store the packets received by the input network interface,

wherein the buffer includes a first portion configured or designed to be used to remove the jitter from the packets, and a second portion, wherein the first and second portions are variably sized according to the amount of jitter in the packets;

a multiplexer designed or configured to schedule packets from the multiple bitstreams, scan packets in the second portion with a look ahead window, wherein the size of the look ahead window decreases with an increasing amount of jitter, and adjust allocation of bandwidth on the channel based on the buffer scan,

an output network interface designed or configured to be in digital communication with the multiplexer and to output the packets from the bitstreams onto the channel.

2. The network device of claim 1 further comprising a bit rate converter designed or configured to transcode compressed video data.

3. The network device of claim 1 wherein the input network interface and the output network interface are included in a combined network interface.

4. The network device of claim 1 wherein the input network interface is designed or configured to receive compressed video data according to an IP protocol.

5. The network device of claim 1 wherein the buffer has a size that produces from a 50 millisecond to a 2500 millisecond delay between receiving the packets and processing of the packets by the multiplexer.

6. The network device of claim 5 wherein the buffer has a size that produces from a 350 millisecond to a 800 millisecond delay between receiving the packets and processing of the packets by the multiplexer.

7. The network device of claim 1 wherein the network device receives the multiple bitstreams from multiple channels.

8. The network device of claim 7 wherein the network device comprises a dedicated buffer for each of the multiple channels, wherein each buffer:

stores the packets received for a channel and removes jitter from the packets; and

the multiplexer is further designed or configured to scan packets in each buffer to adjust allocation of bandwidth on the channel.

9. The network device of claim 1 wherein one of the multiple bitstreams includes a multiplexed data and the multiplexer implements a re-multiplex scheme.

10. The network device of claim 9 wherein the multiplexer is included in a statistical re-multiplexer.

11. The network device of claim 1 wherein the size of the second portion is not varied below a predetermined minimum size.

12. A method for transmitting compressed video data onto a channel, the method comprising:

receiving multiple bitstreams, at least one bitstream of the multiple bitstreams including compressed video data contained in packets that have jitter;

storing the packets in a buffer in a manner that reduces the jitter;

scanning the buffer using a look ahead window, wherein the size of the look ahead window decreases with an increasing amount of jitter;

scheduling the packets from the multiple bitstreams; and

transmitting data packets from each of the multiple bitstreams onto the channel.

13. The method of claim 12 wherein one of the multiple bitstreams has previously been multiplexed.

14. The method of claim 12 wherein the packets are scheduled according to a statistical multiplexing scheme.

15. The method of claim 12 wherein the buffer has a size that produces from a 50 millisecond to a 2500 millisecond delay between receiving the data and scheduling.

16. The method of claim 15 wherein the at least one buffer has a size that produces from a 350 millisecond to a 800 millisecond delay between receiving the data and scheduling.

17. The method of claim 12 wherein scheduling the packets from the multiple bitstreams comprises adjusting allocation of bandwidth on the channel based on the buffer scan.

18. The method of claim 12 wherein the packets are received according to an IP protocol.

19. A network device for transmitting compressed video data onto a channel, the network device comprising:

means for receiving multiple bitstreams, at least one bitstream of the multiple bitstreams including compressed video data contained in packets that have jitter;

means for storing the packets in a buffer in a manner that reduces the jitter;

means for scanning the buffer using a look ahead window, wherein the size of the look ahead window decreases with an increasing amount of jitter;

means for scheduling the packets from the multiple bitstreams; and

means for transmitting data packets from each of the multiple bitstreams onto the channel.

20. The network device of claim 19 further comprising means for adjusting allocation of bandwidth on the channel based on the buffer scan.

21. A computer readable medium including computer readable instructions for processing compressed video when executed by a processor, the instructions comprising:

instructions for receiving multiple bitstreams, at least one bitstream of the multiple bitstreams including compressed video data contained in packets that have jitter;

instructions for storing the packets in a buffer in a manner that reduces the jitter;

instructions for scanning the buffer using a look ahead window, wherein the size of the look ahead window decreases with an increasing amount of jitter;

instructions for scheduling the packets from the multiple bitstreams; and

instructions for transmitting data packets from each of the multiple bitstreams onto the channel.