Efficient available bandwidth usage in transmission of compressed video data

• US 7,292,602 B1
• Filed: 12/27/2001
• Issued: 11/06/2007
• Est. Priority Date: 12/27/2001
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Liu, Xiaomei, Ramakrishnan, Sangeeta
• Primary Examiner(s): Phunkulh; Bob A.
• Application Number:
  US10/034,057
• Time in Patent Office: 2,140 Days
• Field of Search: None
• US Class Current: 370/468
• CPC Class Codes: H04J 3/047 Distributors with transistors or integrated circuits
• CPC Class Codes: H04N 21/2221 being a cable television head-end CATV in broadcast systems H04H20/78
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/2343 involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements video transcoding H04N19/40; media packet handling at the source H04L65/762
• 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 21/238 Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams hybrid fiber coaxial [HFC] networks for downstream channel allocation for video distribution H04L12/2801; flow control in packet networks H04L47/10; real-time communication protocols in data switching networks H04L65/00; scheduling or organising the servicing of application requests H04L67/60
• CPC Class Codes: H04N 21/2385 Channel allocation H04N21/266 takes precedence; Bandwidth allocation H04N21/24 takes precedence ; allocation of channels according to the instantaneous demands of the users in time-division multiplex systems H04J3/1682; admission control, resource allocation in open networks H04L12/5692; arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896; negotiating bandwidth in wireless networks H04W28/16
• CPC Class Codes: H04N 21/2401 Monitoring of the client buffer
• CPC Class Codes: H04N 21/2402 Monitoring of the downstream path of the transmission network, e.g. bandwidth available traffic monitoring in data switching networks H04L43/00; monitoring data switching networks utilization H04L43/0876
• CPC Class Codes: H04N 21/2662 Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
• CPC Class Codes: H04N 21/4347 Demultiplexing of several 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 multiplexing and transmitting video data. The systems and methods use excess bandwidth in a channel available after meeting minimum transmission requirements for all bitstreams. A network device of the invention flexibly allocates this available bandwidth to minimize further rate reduction. More specifically, the network device periodically determines the available bandwidth, and divides the available bandwidth among multiple incoming bitstreams being multiplexed in order to increase downstream decoder buffer levels. By maintaining increased decoder buffer levels, future rate reduction of the video data may be avoided or applied to a lesser degree. Minimizing rate reduction in this manner improves bandwidth usage efficiency, and thus improves video data transmission and end-user output video quality.

Claims

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

a bit rate converter designed or configured to transcode compressed video data from multiple bitstreams to produce multiple transcoded bitstreams;

a multiplexer designed or configured to

a) schedule packets from the multiple transcoded bitstreams in a first pass of scheduling in a scheduling period;

b) determine if bandwidth is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling, the available bandwidth including a difference between a bandwidth on the channel and a sum of a bandwidth needed for all of the packets from the multiple transcoded bitstreams scheduled in the first pass of scheduling, and if so, allocate additional packets from the multiple transcoded bitstreams in a second pass of scheduling in the scheduling period to use the determined available bandwidth on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling; and

a network interface designed or configured to output the packets from the multiple transcoded bitstreams onto the channel.

2. The network device of claim 1 wherein the multiplexer comprises a bandwidth arbitrator that is designed or configured to divide the available bandwidth among the multiple bitstreams.

3. The network device of claim 2 wherein the bandwidth arbitrator periodically determines and allocates the available bandwidth on a temporal basis.

4. The network device of claim 2 wherein the bandwidth arbitrator periodically determines a decoder buffer level for each of the bitstreams.

5. The network device of claim 2 wherein the multiplexer is designed or configured to alter the scheduling of packets according to the bit rate of incoming bitstreams.

6. The network device of claim 2 further comprising a rate controller, coupled to the bandwidth arbitrator and the bit rate converter, and designed or configured to output a control signal that determines the amount of rate reduction when transcoding the compressed video data.

7. The network device of claim 1 wherein a processor in the network device is designed or configured to model downstream decoder buffer levels corresponding to each of the bitstreams.

8. The network device of claim 1 wherein the multiplexer is included in a statistical multiplexer.

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

receiving multiple bitstreams, each bitstream including compressed video data contained in packets;

transcoding the compressed video data from the multiple bitstreams to produce multiple transcoded bitstreams;

performing a first pass of scheduling in a scheduling period to schedule packets from the multiple transcoded bitstreams;

determining if bandwidth is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling, the available bandwidth including a difference between a bandwidth on the channel and a sum of a bandwidth needed for all of the packets from the multiple trans coded bitstreams scheduled in the first pass of scheduling;

performing a second pass of scheduling in the scheduling period to allocate additional packets from the multiple transcoded bitstreams to use the determined available bandwidth on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling if there is available bandwidth on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling; and

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

10. The method of claim 9 wherein the available bandwidth is determined on a periodic basis.

11. The method of claim 10 wherein the available bandwidth is periodically determined on one of a temporal, bit or a packet basis.

12. The method of claim 11 wherein the available bandwidth is periodically determined about every 10 milliseconds to about every 250 milliseconds.

13. The method of claim 9 wherein the available bandwidth is allocated according to a minimum bandwidth requirement for a downstream decoder.

14. The method of claim 9 wherein the available bandwidth is allocated inversely proportional to a downstream decoder buffer level.

15. The method of claim 9 further comprising modeling a downstream decoder buffer level corresponding to one of the multiple bitstreams.

16. The method of claim 15 wherein the available bandwidth is allocated to a bitstream having a lower modeled downstream decoder buffer level than another bitstream having a higher modeled downstream decoder buffer level.

17. The method of claim 15 wherein the available bandwidth on the channel is allocated inversely proportional to the modeled downstream decoder buffer level.

18. The method of claim 9 wherein the available bandwidth on the channel is allocated proportional to the minimum bandwidth requirement of each downstream decoder buffer level.

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

means for receiving multiple bitstreams, each bitstream including compressed video data contained in packets;

means for transcoding compressed video data from the multiple bitstreams to produce multiple transcoded bitstreams;

means for performing a first pass of scheduling in a scheduling period to schedule packets from the multiple transcoded bitstreams;

means for determining if bandwidth is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling, the available bandwidth including a difference between a bandwidth on the channel and a sum of a bandwidth needed for all of the packets from the multiple transcoded bitstreams scheduled in the first pass of scheduling;

means for performing a second pass of scheduling in the scheduling period to allocate additional packets from the multiple transcoded bitstreams to use the determined available bandwidth on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling if there is bandwidth that is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling; and

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

20. The network device of claim 19 further comprising means, coupled to the means for scheduling and the means for transcoding, for outputting a control signal that determines the amount of rate reduction when transcoding the compressed video data.

21. The network device of claim 19 further comprising means for modeling a downstream decoder buffer level corresponding to one of the multiple bitstreams.

22. A computer readable medium storing computer executable instructions for transmitting compressed video data onto a channel, the instructions comprising:

instructions for receiving multiple bitstreams, each bitstream including compressed video data contained in packets;

instructions for transcoding compressed video data from the multiple bitstreams to produce multiple transcoded bitstreams;

instructions for performing a first pass of scheduling in a scheduling period to schedule packets from the multiple transcoded bitstreams;

instructions for determining if bandwidth is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling, the available bandwidth including a difference between a bandwidth on the channel and a sum of a bandwidth needed for all of the packets from the multiple transcoded bitstreams scheduled in the first pass of scheduling;

instructions for performing a second pass of scheduling in the scheduling period to allocate additional packets from the multiple transcoded bitstreams to use the determined available bandwidth on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling if there is bandwidth that is available on the channel after the multiple transcoded bitstreams have been scheduled by the multiplexer in the first pass of scheduling; and

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