Multi-channel audio encoding/decoding with parametric compression/decompression and weight factors
The invention includes several techniques and tools, which can be used in combination or separately. For example, an audio encoder can encode information directly using coding processes that include a windowed overlapped transform, a selective multi-channel transform, scalar quantization and entropy encoding. The audio encoder can also encode information parametrically according to a parametric compression mode that accounts for audibility of distortion according to an auditory model. A corresponding audio decoder can decode first information directly and second information according to the parametric mode.
1. In an audio decoder, a method comprising:
receiving, at the audio decoder, encoded information in a bit stream for audio in multiple channels, wherein the encoded information comprises:
first encoded information encoded directly using coding processes that include a windowed overlapped transform, a selective multi-channel transform, scalar quantization and entropy encoding; and
second encoded information encoded parametrically according to a parametric compression mode that accounts for audibility of distortion according to an auditory model, wherein the second encoded information includes a set of parameters that represent plural weight factors;
with the audio decoder, decoding the first encoded information;
with the audio decoder, decoding the second encoded information according to a parametric decompression mode, wherein the parametric decompression mode includes inverse quantizing the set of parameters that represent the plural weight factors, and wherein the parametric decompression mode further includes:
computing linear prediction coefficients, wherein the linear prediction coefficients modify results of the decoding the first encoded information;
with the audio decoder, reconstructing the audio using results of the decoding first encoded information and results of the decoding the second encoded information; and
from the audio decoder, outputting the reconstructed audio.
2. The method of claim 1 wherein each of the plural weight factors represented by the set of parameters provides a weight value for one or more frequency bands for a time window of the audio.
3. The method of claim 2 wherein the plural weight factors provide the weight values for an independently coded left channel of the multiple channels, and wherein the second encoded information further includes a second set of parameters that represent plural weight factors for an independently coded right channel of the multiple channels.
4. The method of claim 2 wherein the plural weight factors provide the weight values for a jointly coded channel.
5. The method of claim 1 further comprising:
selecting the parametric decompression mode from among multiple available decompression modes for the second encoded information.
6. A computer-readable storage medium storing computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
receiving encoded information in a bit stream for audio in multiple channels, wherein the encoded information comprises:
first encoded information encoded directly using coding processes that include a windowed overlapped transform, a selective multi-channel transform, scalar quantization and entropy encoding; and
second encoded information encoded parametrically according to a parametric compression mode that accounts for audibility of distortion according to an auditory model, wherein the second encoded information includes a set of parameters that represent plural weight factors;
decoding the first encoded information;
decoding the second encoded information according to a parametric decompression mode, wherein the parametric decompression mode includes inverse quantizing the set of parameters that represent the plural weight factors, and wherein the parametric decompression mode further includes:
computing linear prediction coefficients, wherein the linear prediction coefficients modify results of the decoding the first encoded information;
reconstructing the audio using results of the decoding first encoded information and results of the decoding the second encoded information; and
outputting the reconstructed audio.
7. The computer-readable storage medium of claim 6 wherein each of the plural weight factors represented by the set of parameters provides a weight value for one or more frequency bands for a time window of the audio.
8. The computer-readable storage medium of claim 7 wherein the plural weight factors provide the weight values for an independently coded left channel of the multiple channels, and wherein the second encoded information further includes a second set of parameters that represent plural weight factors for an independently coded right channel of the multiple channels.
9. The computer-readable storage medium of claim 7 wherein the plural weight factors provide the weight values for a jointly coded channel.
10. The computer-readable storage medium of claim 6 wherein the method further comprises:
selecting the parametric decompression mode from among multiple available decompression modes for the second encoded information.