Forward time-domain aliasing cancellation with application in weighted or original signal domain
The present invention relates to methods and devices for forward time-domain aliasing cancellation in a coded signal transmitted from a coder to a decoder. Information related to correction of the time-domain aliasing in the coded signal is calculated at the coder and added in a bitstream sent from the coder to the decoder. The decoder receives the bitstream and cancels the time-domain aliasing in the coded signal in response to the information comprised in the bitstream. The information may be representative of a difference between a frame of audio signal to be encoded in a first coding mode and a decoded signal from the frame including time-domain aliasing effects.
1. A method for forward cancelling time-domain aliasing in a coded signal received in a bitstream at a decoder, comprising:
receiving in the bitstream at the decoder, from a coder, additional information related to correction of the time-domain aliasing in the coded signal, wherein the additional information is representative of a forward aliasing cancellation (FAC) correction signal related to a difference signal based on a difference between a signal to be coded upon transition from a first coding mode to a second coding mode and a synthesis signal obtained using the first coding mode; and
in the decoder, cancelling the time-domain aliasing in the coded signal in response to the additional information.
2. The method of claim 1 , used in transitions between a frame using a rectangular, non-overlapping window and a frame using a non-rectangular, overlapping window.
3. The method of claim 1 , wherein the FAC correction signal is a windowed, or windowed and folded FAC correction signal.
4. The method of claim 1 , wherein the FAC correction signal is transform coded using a transform for coding a frame using a non-rectangular, overlapping window.
5. The method of claim 1 , wherein the first coding mode is a Code Excited Linear Prediction (CELP) mode and the second coding mode is a transform coding mode.
6. The method of claim 1 , wherein the difference signal is based on a difference between the signal to be coded and the synthesis signal concatenated with a zero-input response of a synthesis filter of the first coding mode.
7. The method of claim 1 , wherein cancelling the time-domain aliasing comprises, at the decoder:
decoding the difference signal; and
re-computing the FAC correction signal using the synthesis signal and the decoded difference signal.
8. The method of claim 1 , wherein cancelling the time-domain aliasing comprises, at the decoder:
decoding the FAC correction signal; and
adding the decoded FAC correction signal to the coded signal.
9. The method of claim 1 , wherein the FAC correction signal is quantized using scale factors used in non-rectangular, overlapping windows.
10. A method for forward cancelling time-domain aliasing in a coded signal for transmission from a coder to a decoder, comprising:
in the coder, calculating additional information related to correction of the time-domain aliasing in the coded signal, wherein calculating the additional information comprises producing a forward aliasing cancellation (FAC) correction signal related to a difference signal based on a difference between a signal to be coded upon transition from a first coding mode to a second coding mode and a synthesis signal obtained using the first coding mode; and
sending in a bitstream, from the coder to the decoder, the additional information related to the correction of the time-domain aliasing in the coded signal.
11. The method of claim 10 , used in transitions between a frame using a rectangular, non-overlapping window and a frame using a non-rectangular, overlapping window.
12. The method of claim 10 , wherein calculating the additional information comprises windowing, or windowing and folding the FAC correction signal.
13. The method of claim 10 , wherein calculating the additional information comprises transform coding the FAC correction signal using a transform for coding a frame using a non-rectangular, overlapping window.
14. The method of claim 10 , wherein the first coding mode is a Code Excited Linear Prediction (CELP) mode and the second coding mode is a transform coding mode.
15. The method of claim 10 , wherein the difference signal is based on a difference between the signal to be coded and the synthesis signal concatenated with a zero-input response of the synthesis filter of the first coding mode.
16. The method of claim 10 , comprising quantizing the FAC correction signal using scale factors used in non-rectangular, overlapping windows.
17. The method of claim 16 , comprising subtracting a quantization error of a transform-coded frame from the FAC correction signal prior to quantization of the FAC correction signal.
18. A device for forward cancelling time-domain aliasing in a coded signal received in a bitstream, comprising:
a receiver, from a bitstream from a coder, of additional information related to correction of the time-domain aliasing in the coded signal, wherein the additional information comprises a forward aliasing cancellation (FAC) correction signal related to a difference signal based on a difference between a signal to be coded upon transition from a first coding mode to a second coding mode and a synthesis signal obtained using the first coding mode; and
a canceller of the time-domain aliasing in the coded signal in response to the additional information.
19. The device of claim 18 , used in transitions between a frame using a rectangular, non-overlapping window and a frame using a non-rectangular, overlapping window.
20. The device of claim 18 , wherein the FAC correction signal is a windowed, or windowed and folded FAC correction signal.
21. The device of claim 18 , wherein the FAC correction signal is transform coded using a transform for coding a frame using a non-rectangular, overlapping window.
22. The device of claim 18 , wherein the first coding mode is a Code Excited Linear Prediction (CELP) mode and the second coding mode is a transform coding mode.
23. The device of claim 18 , wherein difference signal is based on a difference between the signal to be coded and the synthesis signal concatenated with a zero-input response of a synthesis filter of the first coding mode.
24. The device of claim 18 , wherein the canceller, at the decoder:
decodes the difference signal; and
re-computes the FAC correction signal using the synthesis signal and the decoded difference signal.
25. The device of claim 18 , wherein the canceller, at the decoder:
decodes the FAC correction signal;
adds the decoded FAC correction signal to the coded signal.
26. The device of claim 18 , wherein the FAC correction signal is quantized using scale factors used in non-rectangular, overlapping windows.
27. A device for forward time-domain aliasing cancellation in a coded signal for transmission to a decoder, comprising:
a calculator of additional information related to correction of the time-domain aliasing in the coded signal, wherein the calculator of the additional information comprises a producer of a forward aliasing cancellation (FAC) correction signal related to a difference signal based on a difference between a signal to be coded upon transition from a first coding mode to a second coding mode and a synthesis signal obtained using the first coding mode; and
a transmitter for sending in the bitstream, to a decoder, the additional information related to the correction of the time-domain aliasing in the coded signal.
28. The device of claim 27 , used in transitions between a frame using a rectangular, non-overlapping window and a frame using a non-rectangular, overlapping window.
29. The device of claim 27 , wherein the producer of the FAC correction signal windows, or windows and folds the FAC correction signal.
30. The device of claim 27 , wherein the producer of the FAC correction signal transform codes the FAC correction signal using a transform for coding a frame using a non-rectangular, overlapping window.
31. The device of claim 27 , wherein the first coding mode is a Code Excited Linear Prediction (CELP) mode and the second coding mode is a transform coding mode.
32. The device of claim 27 , wherein the difference signal is based on a difference between the signal to be coded and the synthesis signal concatenated with a zero-input response of the synthesis filter of the first coding mode.
33. The device of claim 27 , comprising a quantizer of the FAC correction signal using scale factors used in non-rectangular, overlapping windows.
34. The device of claim 33 , comprising a subtractor of an error of a synthesized TCX frame from the FAC correction signal prior to quantization of the FAC correction signal.