Apparatus and method for generating a multi-channel synthesizer control signal, multi-channel synthesizer, method of generating an output signal from an input signal and machine-readable storage medium

• US 8,532,999 B2
• Filed: 06/13/2011
• Issued: 09/10/2013
• Est. Priority Date: 04/15/2005
• Status: Active Grant

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated), Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V., Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Neusinger, Matthias, Herre, Juergen, Disch, Sascha, Purnhagen, Heiko, Kjoerling, Kristofer, Engdegard, Jonas, Breebaart, Jeroen, Schuijers, Erik, Oomen, Werner
• Primary Examiner(s): Desir, Pierre-Louis
• Assistant Examiner(s): KOVACEK, DAVID M
• Application Number:
  US13/158,863
• Publication Number:
  US 20110235810A1
• Time in Patent Office: 820 Days
• Field of Search: 704200-201, 704500-501, 704503-504, 704E19001-E19049
• US Class Current: 704/500
• 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: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation
• 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

An apparatus and a method for generating a multi-channel synthesizer control signal, a multi-channel synthesizer, a method of generating an output signal from an input signal and a machine-readable storage medium are provided. On an encoder-side, a multi-channel input signal is analyzed for obtaining smoothing control information, which is to be used by a decoder-side multi-channel synthesis for smoothing quantized transmitted parameters or values derived from the quantized transmitted parameters for providing an improved subjective audio quality in particular for slowly moving point sources and rapidly moving point sources having tonal material such as fast moving sinusoids.

Claims

1. A spatial audio encoder, comprising:

an apparatus for generating a multi-channel synthesizer control signal, the apparatus including;

a signal analyzer for analyzing a multi-channel input signal;

a smoothing information calculator for determining smoothing control information in response to the signal analyzer, the smoothing information calculator being operative to determine the smoothing control information such that, in response to the smoothing control information, a synthesizer-side post-processor generates a post-processed reconstruction parameter or a post-processed quantity derived from the reconstruction parameter for a time portion of an input signal to be processed; and

a data generator for generating a control signal representing the smoothing control information as the multi-channel synthesizer control signal;

a downmixer configured for generating a downmix signal from the multi-channel input signal; and

a spatial parameter extraction device for extracting spatial parameters from the multi-channel input signal,

wherein the spatial audio encoder is configured for transmitting or storing the downmix signal, the spatial parameters and the multi-channel synthesizer control signal.

2. The spatial audio encoder in accordance with claim 1, in which the signal analyzer is operative to analyze a change of a multi-channel signal characteristic from a first time portion of the multi-channel input signal to a later second time portion of the multi-channel input signal, and

in which the smoothing information calculator is operative to determine a smoothing time constant information based on the analyzed change.

3. The spatial audio encoder in accordance with claim 2, in which the data generator is operative to generate, as the smoothing control information, a signal indicating a certain smoothing time constant value from a set of values known to the synthesizer-side post-processor.

4. Apparatus in accordance with claim 2, in which the signal analyzer is operative to determine whether a point source exists based on an inter-channel coherence parameter for a multi-channel input signal time portion, and

in which the smoothing information calculator or the data generator are only active when the signal analyzer has determined that a point source exists.

5. The spatial audio encoder in accordance with claim 2, in which the signal analyzer is operative to generate an inter-channel level difference or inter-channel intensity difference for several time instants, and

in which the smoothing information calculator is operative to calculate a smoothing time constant, which is inversely proportional to a slope of a curve of the inter-channel level difference or inter-channel intensity difference parameters.

6. The spatial audio encoder in accordance with claim 2, in which the smoothing information calculator is operative to calculate a single smoothing time constant for a group of several frequency bands, and

in which the data generator is operative to indicate information for one or more bands in the group of several frequency bands, in which the synthesizer-side post-processor is to be deactivated.

7. The spatial audio encoder in accordance with claim 1, in which the data generator is operative to generate a synthesizer activation signal indicating whether the synthesizer-side post-processor is to work using information transmitted in a data stream or using information derived from synthesizer-side signal analysis.

8. The spatial audio encoder in accordance with claim 1, in which the smoothing information calculator is operative to calculate a change in a position of a point source for subsequent multi-channel input signal time portions, and

in which the data generator is operative to output a control signal indicating that the change in position is below a predetermined threshold so that smoothing is to be applied by the synthesizer-side post-processor.

9. The spatial audio encoder in accordance with claim 1, in which the smoothing information calculator is operative to perform an analysis by synthesis processing.

10. The spatial audio encoder in accordance with claim 9, in which the smoothing information calculator is operative:

to calculate several time constants,

to simulate a synthesizer-side post-processing using the several time constants,

to select a time constant, which results in values for subsequent frames, which shows the smallest deviation from non-quantized corresponding values.

11. The spatial audio encoder in accordance with claim 9, in which different test pairs are generated, in which a test pair has a smoothing time constant and a certain quantization rule, and

in which the smoothing information calculator is operative to select quantized values using a quantization rule and the smoothing time constant from the pair, which results in a smallest deviation between post-processed values and non-quantized corresponding values.

12. A spatial audio encoding method, comprising:

a method of generating a multi-channel synthesizer control signal, the method of generating a multi-channel synthesizer control signal, comprising;

analyzing a multi-channel input signal;

determining smoothing control information in response to the signal analyzing step, such that, in response to the smoothing control information, a post-processing step generates a post-processed reconstruction parameter or a post-processed quantity derived from the reconstruction parameter for a time portion of an input signal to be processed; and

generating a control signal representing the smoothing control information as the multi-channel synthesizer control signal;

generating a downmix signal from the multi-channel input signal;

extracting spatial parameters from the multi-channel input signal; and

transmitting or storing the downmix signal, the spatial parameters and the multi-channel synthesizer control signal.

13. A multi-channel synthesizer for generating an output signal from an input signal, the input signal having at least one input channel and a sequence of quantized reconstruction parameters and a multi-channel synthesizer control signal multiplexed with the sequence of quantized reconstruction parameters, the quantized reconstruction parameters being quantized in accordance with a quantization rule, and being associated with subsequent time portions of the input signal, the output signal having a number of synthesized output channels, and the number of synthesized output channels being greater than the number of input channels, comprising:

a control signal provider for providing the multi-channel synthesizer control signal having smoothing control information by demultiplexing the input signal, wherein the multi-channel synthesizer control signal representing the smoothing control information is associated to the at least one input channel;

a post-processor for determining, in response to the control signal, the post-processed reconstruction parameter or the post-processed quantity derived from the reconstruction parameter for a time portion of the input signal to be processed, wherein the post-processor is operative to determine the post-processed reconstruction parameter or the post-processed quantity such that the value of the post-processed reconstruction parameter or the post-processed quantity is different from a value obtainable using requantization in accordance with the quantization rule; and

a multi-channel reconstructor for reconstructing a time portion of the number of synthesized output channels using the time portion of the input channel and the post-processed reconstruction parameter or the post-processed value.

14. The multi-channel synthesizer in accordance with claim 13, in which the control signal includes a decoder activation signal indicating, whether the post-processor is to work using the multi-channel synthesizer control signal multiplexed with the sequence of quantized reconstruction parameters or using information derived from a decoder-side signal analysis, and

in which the post-processor is operative to work using the smoothing control information or based on a decoder-side signal analysis in response to the control signal.

15. The multi-channel synthesizer in accordance with claim 14, in which the smoothing control information indicates a smoothing time constant, and

in which the post-processor is operative to perform a low-pass filtering, wherein a filter characteristic is set in response to the smoothing time constant.

16. The multi-channel synthesizer in accordance with claim 14, further comprising an input signal analyzer for analyzing the input signal to determine a signal characteristic of the time portion of the input signal to be processed,

wherein the post-processor is operative to determine the post-processed reconstruction parameter depending on the signal characteristic,

wherein the signal characteristic is a tonality characteristic or a transient characteristic of the portion of the input signal to be processed.

17. The multi-channel synthesizer in accordance with claim 13, in which the control signal includes smoothing control information for each band of a plurality of bands of the at least one input channel, and

in which the post-processor is operative to perform post-processing in a band-wise manner in response to the control signal.

18. A method of generating an output signal from an input signal, the input signal having at least one input channel and a sequence of quantized reconstruction parameters and a multi-channel synthesizer control signal multiplexed with the sequence of quantized reconstruction parameters, the quantized reconstruction parameters being quantized in accordance with a quantization rule, and being associated with subsequent time portions of the input signal, the output signal having a number of synthesized output channels, and the number of synthesized output channels being greater than the number of input channels, comprising:

providing the multi-channel synthesizer control signal having the smoothing control information by demultiplexing the input signal, wherein the multi-channel synthesizer control signal representing the smoothing control information is associated to the at least one input channel;

determining, in response to the control signal, the post-processed reconstruction parameter or the post-processed quantity derived from the reconstruction parameter for a time portion of the input signal to be processed; and

reconstructing a time portion of the number of synthesized output channels using the time portion of the input channel and the post-processed reconstruction parameter or the post-processed value.

19. A non-transitory storage medium having stored thereon a computer program for performing, when running on a computer, a spatial audio encoding method, comprising:

a method of generating a multi-channel synthesizer control signal, the method of generating a multi-channel synthesizer control signal comprising;

analyzing a multi-channel input signal;

determining smoothing control information in response to the signal analyzing step, such that, in response to the smoothing control information, a post-processing step generates a post-processed reconstruction parameter or a post-processed quantity derived from the reconstruction parameter for a time portion of an input signal to be processed; and

generating a control signal representing the smoothing control information as the multi-channel synthesizer control signal;

generating a downmix signal from the multi-channel input signal;

extracting spatial parameters from the multi-channel input signal; and

transmitting or storing the downmix signal, the spatial parameters and the multi-channel synthesizer control signal.

20. A non-transitory storage medium having stored thereon a computer program for performing, when running on a computer, a method of generating an output signal from an input signal, the input signal having at least one input channel and a sequence of quantized reconstruction parameters and a multi-channel synthesizer control signal multiplexed with the sequence of quantized reconstruction parameters, the quantized reconstruction parameters being quantized in accordance with a quantization rule, and being associated with subsequent time portions of the input signal, the output signal having a number of synthesized output channels, and the number of synthesized output channels being greater than the number of input channels, comprising:

providing the multi-channel synthesizer control signal having the smoothing control information by demultiplexing the input signal, wherein the multi-channel synthesizer control signal representing the smoothing control information is associated to the at least one input channel;

determining, in response to the control signal, the post-processed reconstruction parameter or the post-processed quantity derived from the reconstruction parameter for a time portion of the input signal to be processed; and

reconstructing a time portion of the number of synthesized output channels using the time portion of the input channel and the post-processed reconstruction parameter or the post-processed value.