Temporal and spatial shaping of multi-channel audio signals

• US 20070081597A1
• Filed: 02/27/2006
• Published: 04/12/2007
• Est. Priority Date: 10/12/2005
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.), Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V., Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V., Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Herre, Juergen, Disch, Sascha, Neusinger, Matthias, Breebaart, Dirk Jeroen, Hotho, Gerard
• Granted Patent: US 7,974,713 B2
• Time in Patent Office: Days
• US Class Current: 375/242
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

A selected channel of a multi-channel signal which is represented by frames composed from sampling values having a high time resolution can be encoded with higher quality when a wave form parameter representation representing a wave form of an intermediate resolution representation of the selected channel is derived, the wave form parameter representation including a sequence of intermediate wave form parameters having a time resolution lower than the high time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate. The wave form parameter representation with the intermediate resolution can be used to shape a reconstructed channel to retrieve a channel having a signal envelope close to that one of the selected original channel. The time scale on which the shaping is performed is shorter than the time scale of a framewise processing, thus enhancing the quality of the reconstructed channel. On the other hand, the shaping time scale is larger than the time scale of the sampling values, significantly reducing the amount of data needed by the wave form parameter representation.

Claims

1. Decoder for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, comprising:

an upmixer for generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

a shaper for shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.

2. Decoder in accordance with claim 1, in which the upmixer is further operative to derive an intermediate resolution representation of the base signal.

3. Decoder in accordance with claim 2, in which the upmixer is operative to derive the intermediate resolution representation of the base signal using a filter bank, wherein the intermediate resolution representation of the base signal is derived in a filter bank domain.

4. Decoder in accordance with claim 3, in which the filter bank is a complex modulated filter bank.

5. Decoder in accordance with claim 1, in which the upmixer is having one or more decorrelators for deriving one or more decorrelated signals from the base signal.

6. Decoder in accordance with claim 5, in which the upmixer is operative such that the generation of the upmixed channels includes a linear combination of the channels of the base signal and of the one or more decorrelated signals.

7. Decoder in accordance with claim 6, in which the shaper is operative to shape a selected upmixed channel such that a first part of the selected upmixed channel derived from the base signal is shaped independently from a second part of the selected upmixed channel derived from the one or more decorrelated signals.

8. Decoder in accordance with claim 1, in which the shaper is operative to use intermediate wave form parameters describing a signal strength measure of the intermediate resolution representation of the selected channel.

9. Decoder in accordance with claim 8, in which the shaper is operative to use intermediate wave form parameters describing a signal strength measure having an amplitude or an energy measure.

10. Decoder in accordance with claim 1, in which the upmixer is operative to derive an intermediate resolution representation of the base signal, used to generate the upmixed channels;

and

in which the shaper is operative to derive a reference wave form parameter representation of the intermediate resolution representation of the base signal for shaping the selected upmixed signal using the wave form parameter representation and the reference wave form parameter representation.

11. Decoder in accordance with claim 10, in which the shaper is operative to shape the selected upmixed channel such that the shaping comprises a combination of the parameters from the wave form parameter representation and from the reference wave form parameter representation.

12. Decoder in accordance with claim 10, in which the shaper is operative to derive a spectrally flat representation of the intermediate resolution representation of the base signal, the spectrally flat representation having a flat frequency spectrum, and to derive the reference wave form parameter representation from the spectrally flat representation.

13. Decoder in accordance with claim 1, in which the shaper is further adapted to shape the selected upmixed channel using additional parameters having the low time resolution.

14. Decoder in accordance with claim 1, further having an output interface to generate the multi-channel output signal having the high time resolution using the shaped selected upmixed channel.

15. Decoder in accordance with claim 14, in which the output interface is operative to generate the multi-channel output signal such that the generation of the multi-channel output signal comprises a synthesis of a filter bank representation of a plurality of shaped upmixed channels resulting in a time domain representation of the plurality of shaped upmixed channels having the high time resolution.

16. Decoder in accordance with claim 1, in which the shaper is having a dequantizer for deriving the wave form parameter representation from a quantized representation of the same, using a dequantization rule having less than 10 quantization steps.

17. Decoder in accordance with claim 16, in which the shaper is having an entropy decoder for deriving the quantized representation of the wave form parameter representation from an entropy encoded representation of the same.

18. Decoder in accordance with claim 17, in which the entropy decoder is operative to use a Huffman codebook for deriving the quantized representation of the wave form parameter representation.

19. Decoder in accordance with claim 3 in which the shaper is operative to shape the selected upmixed channel in the time domain.

20. Encoder for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the encoder comprising:

a time resolution decreaser for deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

a wave form parameter calculator for calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate.

21. Encoder in accordance with claim 20, in which the time resolution decreaser is having a filter bank for deriving the low resolution representation of the channel, the low resolution representation of the channel being derived in a filter bank domain.

22. Encoder in accordance with claim 20, in which the time resolution decreaser is further operative to derive a reference low resolution representation of a base signal derived from the multi-channel signal, the number of channels of the base signal being smaller than the number of channels of the multi-channel signal;

and in which the wave form parameter calculator is operative to calculate the wave form parameters using the reference low resolution representation and the low resolution representation of the channel.

23. Encoder in accordance with claim 22, in which the waveform parameter calculator is operative such that the calculation of the waveform parameters comprises a combination of amplitude measures of the reference low-resolution representation and of the low-resolution representation of the channel.

24. Encoder in accordance with claim 20, in which the waveform parameter calculator is having a quantizer for deriving a quantized representation of the wave form parameters.

25. Encoder in accordance with claim 24, in which the waveform parameter calculator is having an entropy encoder for deriving an entropy encoded representation of the quantized representation of the waveform parameters.

26. Method for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, the method comprising:

generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.

36. Computer having a program code for, when running a computer, performing any of the method claims 26, 27, 32, 33, or 35.

27. Method for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the method comprising:

deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate.

28. Representation of a multi-channel audio signal based on a base signal derived from the multi-channel audio signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected channel of the multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having a time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate.

29. Computer readable storage medium, having stored thereon a representation of a multi-channel audio signal based on a base signal derived from the multi-channel audio signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and

based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected channel of the multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having a time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate.

30. Receiver or audio player having a decoder for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, comprising:

an upmixer for generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

a shaper for shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.

31. Transmitter or audio recorder having an encoder for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the encoder comprising:

a time resolution decreaser for deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

a wave form parameter calculator for calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate.

32. Method of receiving or audio playing, the method having a method for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, the method comprising:

generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.

33. Method of transmitting or audio recording, the method having a method for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the method comprising:

deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate.

34. Transmission system having a transmitter and a receiver, the transmitter having an encoder for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the encoder comprising:

a time resolution decreaser for deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

a wave form parameter calculator for calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate; and

the receiver having a decoder for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, comprising;

an upmixer for generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

a shaper for shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.

35. Method of transmitting and receiving, the method of transmitting having a method for generating a wave form parameter representation of a channel of a multi-channel signal having a frame, the frame comprising sampling values having a sampling period, the method comprising:

deriving a low resolution representation of the channel using the sampling values of a frame, the low resolution representation having low resolution values having associated a low resolution period being larger than the sampling period; and

calculating the wave form parameter representation representing a wave form of the low resolution representation, wherein the wave form parameter calculator is adapted to generate a sequence of wave form parameters having a time resolution lower than a time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate; and

the method of receiving having a method for generating a multi-channel output signal based on a base signal derived from an original multi-channel signal having one or more channels, the number of channels of the base signal being smaller than the number of channels of the original multi-channel signal, the base signal having a frame, the frame comprising sampling values having a high resolution, and based on a wave form parameter representation representing a wave form of an intermediate resolution representation of a selected original channel of the original multi-channel signal, the wave form parameter representation including a sequence of intermediate wave form parameters having an intermediate time resolution lower than the high time resolution of the sampling values and higher than a low time resolution defined by a frame repetition rate, the method comprising;

generating a plurality of upmixed channels having a time resolution higher than the intermediate resolution; and

shaping a selected upmixed channel using the intermediate waveform parameters of the selected original channel corresponding to the selected upmixed channel.