ROBUST DECODER

• US 20090276212A1
• Filed: 07/14/2009
• Published: 11/05/2009
• Est. Priority Date: 05/31/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Sun, Xiaoqin, Khalil, Hosam A., Chen, Wei-Ge, Koishida, Kazuhito, Wang, Tian
• Granted Patent: US 7,962,335 B2
• Time in Patent Office: Days
• US Class Current: 704/226
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 21/045 using thinning out or insertion of a waveform

Abstract

Techniques and tools related to delayed or lost coded audio information are described. For example, a concealment technique for one or more missing frames is selected based on one or more factors that include a classification of each of one or more available frames near the one or more missing frames. As another example, information from a concealment signal is used to produce substitute information that is relied on in decoding a subsequent frame. As yet another example, a data structure having nodes corresponding to received packet delays is used to determine a desired decoder packet delay value.

Claims

1. A computer-implemented method comprising:

processing a bit stream for an audio signal, including, when encountering one or more frames missing from the bit stream, then;

generating a concealment signal comprising an extension signal contribution based at least in part on one or more values associated with an available frame; and

after a threshold duration of the concealment signal, adding a noise contribution to the concealment signal.

2. The method of claim 1, wherein, when encountering the one or more missing frames from the bit stream, the processing further comprises:

gradually decreasing energy of the extension signal contribution along at least part of the audio signal; and

gradually increasing energy of the noise contribution along the at least part of the audio signal.

3. The method of claim 2, wherein gradually decreasing the energy of the extension signal contribution comprises gradually decreasing the energy until the extension signal is imperceptible.

4. The method of claim 2, wherein the energy of the extension signal contribution is gradually decreased and the energy of the noise contribution is gradually increased until the concealment signal consists essentially of a predetermined level of background noise.

5. The method of claim 1, wherein the available frame is a frame subsequent to the one or more frames missing from the bit stream.

6. The method of claim 1, wherein the available frame is a frame prior to the one or more missing frames from the bit stream.

7. The method of claim 1, further comprising combining at least a portion of the concealment signal and a signal associated with a later received packet.

8. The method of claim 7, further comprising selecting a lag of the signal associated with the later received packet so as to increase a correlation value between the concealment signal and the signal associated with the later received packet.

9. A method comprising:

maintaining a data structure, the data structure comprising a set of plural nodes that correspond to packets in a set of received packets, wherein each node of the set of plural nodes comprises;

a delay value for receipt of a corresponding packet of the set of received packets;

a higher value pointer that points to a node of the set of plural nodes with a next higher delay value; and

a lower value pointer that points to a node of the set of plural nodes with a next lower delay value; and

determining a desired decoder packet delay value based at least in part on the data structure.

10. The method of claim 9, further comprising receiving a new packet, wherein maintaining the data structure comprises:

replacing a delay value of an oldest packet out of the set of received packets with a delay value of the new packet;

updating the high value pointer of one or more nodes of the set of plural nodes; and

updating the low value pointer of one or more nodes of the set of plural nodes.

11. The method of claim 9, wherein determining the desired decoder packet delay value comprises:

locating a node of the set of plural nodes comprising a maximum delay value;

searching nodes of the set of plural nodes with successively lower delay values until a desired number of nodes has been searched; and

using the delay value of the last node to be searched as a desired packet delay for the decoder.

12. The method of claim 11, wherein the desired number of nodes corresponds to a predetermined desired packet loss rate.

13. A computing device, comprising:

a decoder configured to produce an audio signal from a bit stream, when encountering one or more frames missing from the bit stream, the decoder operable to;

generate a concealment signal comprising an extension signal contribution based at least in part on one or more values associated with an available frame;

after a threshold duration of the concealment signal, add a noise contribution to the concealment signal; and

combine the concealment signal with the decoded stream for the audio signal.

14. The computing device of claim 13, wherein, when encountering the one or more missing frames from the bit stream, the decoder is further configured to:

decrease energy of the extension signal contribution along at least part of the audio signal; and

increase energy of the noise contribution along the at least part of the audio signal.

15. The computing device of claim 14, wherein decreasing the energy of the extension signal contribution comprises gradually decreasing the energy until the extension signal is imperceptible.

16. The computing device of claim 14, wherein the decoder is configured to gradually decrease the energy of the extension signal contribution and gradually increase the energy of the noise contribution until the concealment signal consists essentially of a predetermined level of background noise.

17. The computing device of claim 13, wherein the available frame is a frame subsequent to the one or more frames missing from the bit stream.

18. The computing device of claim 13, wherein the available frame is a frame prior to the one or more missing frames from the bit stream.

19. The computing device of claim 13, wherein the decoder is configured to combine at least a portion of the concealment signal and a signal associated with a later received packet.

20. The computing device of claim 19, wherein the decoder is configured to select a lag of the signal associated with the later received packet so as to increase a correlation value between the concealment signal and the signal associated with the later received packet.