Frame error concealment

Patent metadata

Field	Value
Publication number	US-9514756-B2
Application number	US-201314767499-A
Country	US
Kind code	B2
Filing date	Nov 12, 2013
Priority date	Feb 13, 2013
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A frame error concealment method based on frames including transform coefficient vectors including the following steps: It tracks (S 11 ) sign changes between corresponding transform coefficients of predetermined sub-vectors of consecutive good stationary frames. It accumulates (S 12 ) the number of sign changes in corresponding sub-vectors of a predetermined number of consecutive good stationary frames. It reconstructs (S 13 ) an erroneous frame with the latest good stationary frame, but with reversed signs of transform coefficients in sub-vectors having an accumulated number of sign changes that exceeds a predetermined threshold.

First claim

The invention claimed is:

1. A frame error concealment method for improving audio quality, the method being performed by a decoder and comprising:
tracking sign changes between corresponding transform coefficients of sub-vectors of consecutive good stationary audio frames including a latest good stationary audio frame, each said sub-vector comprising a plurality of transform coefficients;
accumulating the number of sign changes in corresponding sub-vectors of a number of consecutive good stationary audio frames; and
reconstructing an erroneous frame with the latest good stationary audio frame to produce a reconstructed frame comprising a plurality of sub-vectors each comprising a plurality of transform coefficients, wherein, for each one of the sub-vectors of the reconstructed frame, there is an accumulated number of sign changes for that sub-vector such that each sub-vector has its own accumulated number of sign changes for use in determining the sign of the transform coefficients of the sub-vector, wherein the erroneous frame is reconstructed such that:
for each transform coefficient included in the reconstructed frame, the absolute value of the transform coefficient is identical to the absolute value of a corresponding transform coefficient included in the latest good stationary audio frame,
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that exceeds a threshold, said transform coefficient has a sign that is reversed with respect to the sign of the corresponding transform coefficient included in the latest good stationary audio frame, and
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that is less than the threshold, said transform coefficient has a sign that is the same as the sign of the corresponding transform coefficient included in the latest good stationary audio frame.

2. The method of claim 1 , wherein the threshold depends on the number of consecutive good stationary audio frames.

3. The method of claim 2 , wherein the threshold is assigned a first value for 2 consecutive good stationary audio frames and a second value for 3 consecutive good stationary audio frames.

4. The method claim 1 , including the step of determining stationary of a received frame by determining whether it contains any transients.

5. A decoder comprising a non-transitory computer readable medium storing a computer program for frame error concealment based on frames including transform coefficient vectors, said computer program comprising computer readable code which when run on a processor causes the processor to:
track sign changes between corresponding transform coefficients of sub-vectors of consecutive good stationary audio frames including a latest good stationary audio frame, each said sub-vector comprising a plurality of coefficients;
accumulate the number of sign changes in corresponding sub-vectors of a number of consecutive good stationary audio frames; and
reconstruct an erroneous audio frame with the latest good stationary audio frame to produce a reconstructed frame comprising a plurality of sub-vectors each comprising a plurality of transform coefficients, wherein, for each one of the sub-vectors of the reconstructed frame, there is an accumulated number of sign changes for that sub-vector such that each sub-vector has its own accumulated number of sign changes for use in determining the sign of the transform coefficients of the sub-vector, wherein the erroneous frame is reconstructed such that:
for each transform coefficient included in the reconstructed frame, the absolute value of the transform coefficient is identical to the absolute value of a corresponding transform coefficient included in the latest good stationary audio frame,
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that exceeds a threshold, said transform coefficient has a sign that is reversed with respect to the sign of the corresponding transform coefficient included in the latest good stationary audio frame, and
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that is less than the threshold, said transform coefficient has a sign that is the same as the sign of the corresponding transform coefficient included in the latest good stationary audio frame.

6. A decoder configured for frame error concealment based on frames including transform coefficient vectors, said decoder including a processor and a memory, said memory containing instructions executable by said processor, whereby said decoder is operative to:
track sign changes between corresponding transform coefficients of sub-vectors of consecutive good stationary audio frames including a latest good stationary audio frame, each said sub-vector comprising a plurality of coefficients;
accumulate the number of sign changes in corresponding sub-vectors of a number of consecutive good stationary audio frames; and
reconstruct an erroneous frame with the latest good stationary frame to produce a reconstructed frame comprising a plurality of sub-vectors each comprising a plurality of transform coefficients, wherein, for each one of the sub-vectors of the reconstructed frame, there is an accumulated number of sign changes for that sub-vector such that each sub-vector has its own accumulated number of sign changes for use in determining the sign of the transform coefficients of the sub-vector, wherein the erroneous frame is reconstructed such that:
for each transform coefficient included in the reconstructed frame, the absolute value of the transform coefficient is identical to the absolute value of a corresponding transform coefficient included in the latest good stationary audio frame,
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that exceeds a threshold, said transform coefficient has a sign that is reversed with respect to the sign of the corresponding transform coefficient included in the latest good stationary audio frame, and
for each transform coefficient of the reconstructed frame that is included in a sub-vector that has an accumulated number of sign changes that is less than the threshold, said transform coefficient has a sign that is the same as the sign of the corresponding transform coefficient included in the latest good stationary audio frame.

7. A user terminal including a decoder in accordance with claim 6 .

8. The user terminal of claim 7 , wherein the user terminal is a user equipment.

9. The user terminal of claim 8 , wherein the user equipment is a mobile phone.

10. The user terminal of claim 7 , wherein the user terminal is a personal computer.

11. A audio frame loss concealment method for improving audio quality, the method being performed by a decoder and comprising:
receiving a first good audio frame, said first good audio frame comprising a plurality of bands, each of the plurality of bands comprising a plurality of transform coefficients;
for each one of the plurality of bands, storing a state variable for the band that represents an accumulated a number of transform coefficient sign switches over consecutive audio frames, said consecutive audio frames comprising said first good audio frame and a second good audio frame that preceded the first good audio frame;
determining that a next audio frame immediately following the first good audio frame is lost; and
as a result of determining that the next audi

Assignees

• Ericsson Telefon Ab L M
• ERICSSON TELEFON AB L M (publ)

Inventors

• Näslund Sebastian
• Grancharov Volodya
• Svedberg Jonas

Classifications

• G10L19/005 Primary

  Correction of errors induced by the transmission channel, if related to the coding algorithm · CPC title

• G10L19/025

  Detection of transients or attacks for time/frequency resolution switching · CPC title