Adaptive playout scheduling for multimedia communication

• US 7,324,444 B1
• Filed: 03/05/2003
• Issued: 01/29/2008
• Est. Priority Date: 03/05/2002
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Liang, Yi, Girod, Bernd
• Primary Examiner(s): Shah; Chirag G.
• Application Number:
  US10/383,215
• Time in Patent Office: 1,791 Days
• Field of Search: None
• US Class Current: 370/230
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04L 65/752 adapting media to network capabilities
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

A method of adapting a playout schedule of a stream of media packets according to network and channel conditions includes (a) setting a playout schedule for a next packet i+1 of the stream upon receiving a current packet i; (b) computing a length of the current packet i based at least in part on a target playout schedule for the next packet i+1; (c) scaling packet i if necessary; (d) outputting packet i; and (e) updating the playout schedule for next packet i+1 based at least in part on the playout schedule and the length of current packet i.

Claims

1. A method of adapting a playout schedule of a stream of media packets according to network and channel conditions, the method comprising:

(a) setting a playout schedule for a next packet i+1 of the stream upon receiving a current packet i;

(b) computing a length of the current packet i based at least in part on a target playout schedule for the next packet i+1;

(c) scaling packet i if necessary;

(d) outputting packet i; and

(e) updating the playout schedule for next packet i+1 based at least in part on the playout schedule and the length of current packet i.

2. The method of claim 1, further comprising repeating steps (a) through (e) for additional packets of the stream.

3. The method of claim 1, wherein step (a) comprises estimating the delay of the next packet i+1 and setting the playout schedule for the next packet i+1 based at least in part on the delay.

4. The method of claim 3, wherein estimating the delay comprises using past network delay statistics.

5. The method of claim 3, wherein if the estimated delay of the next packet i+1 is high, the playout schedule for the next packet i+1 is set later to avoid packet loss.

6. The method of claim 3, wherein if the estimated delay of the next packet i+1 is low, the playout schedule for the next packet i+1 is set sooner to reduce buffering delay.

7. The method of claim 1, wherein the playout schedule for next packet i+1 is set such that an expected loss rate of next packet i+1 is not greater than a user-defined value.

8. The method of claim 1, wherein step (c) comprises either expanding, compressing or leaving intact current packet i based on one or more comparisons between a target packet length and one or more thresholds.

9. The method of claim 1, wherein step (c) comprises comparing a difference between a target packet length and at least one of an expansion threshold and a compression threshold in order to determine whether or not to scale current packet i.

10. The method of claim 9, wherein step (c) comprises scaling current packet to a target length if it is determined that current packet i should be scaled.

11. The method of claim 10, wherein scaling current packet i to a target length comprises scaling an audio packet using a time-scale modification technique that modifies a playback rate of the audio packet.

12. The method of claim 10, wherein scaling current packet i to a target length comprises scaling an audio packet using a time-scale modification technique that does not modify the pitch of the audio.

13. The method of claim 10, wherein scaling current packet i to a target length comprises ensuring a continuous media output with no gap or overlap while satisfying the playout schedule of step (a).

14. The method of claim 1, wherein steps (a) through (e) comprise adaptively setting the playout schedule according to monitored channel delay statistics.

15. The method of claim 1, wherein steps (a) through (e) comprise setting the playout schedule during both periods of silence and talkspurts.

16. The method of claim 1, wherein steps (a) through (e) comprise setting the playout schedule and scaling the current packet i on a packet by packet basis.

17. The method of claim 1, wherein steps (a) through (e) comprise scaling current packet i such that current packet i can have a different length.

18. The method of claim 1, further comprising concealing a loss of next packet i+1 if next packet i+1 is not received by a time current packet i is output in step (e).

19. The method of claim 18, further comprising concealing the loss using a time-scale modification technique without modifying a pitch of an audio packet.

20. The method of claim 18, further comprising concealing the loss by extending the current packet i with an expanded target length and outputting an extended packet i at its playout time.