Audio decoder and decoding method using efficient downmixing
AssigneesDolby Laboratories Licensing Corporation, Dolby International AB
InventorsRobin Thesing, James Michael Silva, Robert Loring Andersen
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Abstract
A method, an apparatus, a computer readable storage medium configured with instructions for carrying out a method, and logic encoded in one or more computer-readable tangible medium to carry out actions. The method is to decode audio data that includes N.n channels to M.m decoded audio channels, including unpacking metadata and unpacking and decoding frequency domain exponent and mantissa data; determining transform coefficients from the unpacked and decoded frequency domain exponent and mantissa data; inverse transforming the frequency domain data; and in the case M<N, downmixing according to downmixing data, the downmixing carried out efficiently.
Claims23
A method of operating an audio decoder to decode audio data that includes encoded blocks of N.n channels of audio data to form decoded audio data that includes M.m channels of decoded audio, M≧1, n being the number of low frequency effects channels in the encoded audio data, and m being the number of low frequency effects channels in the decoded audio data, the method comprising:
- accepting the audio data that includes blocks of N.n channels of encoded audio data encoded by an encoding method, the encoding method including transforming N.n channels of digital audio data, and forming and packing frequency-domain exponent and mantissa data;
- and
- decoding the accepted audio data, the decoding including:
- unpacking and decoding the frequency-domain exponent and mantissa data;
- determining transform coefficients from the unpacked and decoded frequency-domain exponent and mantissa data;
- ascertaining whether M<N,
- upon ascertaining that M<N, determining block by block whether to apply frequency-domain downmixing or time-domain downmixing, and upon determining for a particular block to apply frequency-domain downmixing, downmixing in the frequency domain according to downmixing data such that the frequency-domain data is data after downmixing;
- inverse transforming the frequency-domain data and applying further processing to determine sampled audio data;
- and
- if for the case M<N it was determined to apply time-domain downmixing, time-domain downmixing the block of the determined sampled audio data according to downmixing data.
A non-transitory computer-readable medium storing decoding instructions that when executed by one or more processors of an audio decoder cause the decoder to carry out a method of decoding audio data that includes encoded blocks of N.n channels of audio data to form decoded audio data that includes M.m channels of decoded audio, M≧1, n being the number of low frequency effects channels in the encoded audio data, and m being the number of low frequency effects channels in the decoded audio data, the method comprising:
- accepting the audio data that includes blocks of N.n channels of encoded audio data encoded by an encoding method, the encoding method including transforming N.n channels of digital audio data, and forming and packing frequency-domain exponent and mantissa data;
- and
- decoding the accepted audio data, the decoding including:
- unpacking and decoding the frequency-domain exponent and mantissa data;
- determining transform coefficients from the unpacked and decoded frequency-domain exponent and mantissa data;
- ascertaining whether M<N,
- upon ascertaining that M<N, determining block by block whether to apply frequency-domain downmixing or time-domain downmixing, and upon determining for a particular block to apply frequency-domain downmixing, downmixing in the frequency domain according to downmixing data such that the frequency-domain data is data after downmixing;
- inverse transforming the frequency-domain data and applying further processing to determine sampled audio data;
- and
- if for the case M<N it was determined to apply time-domain downmixing, time-domain downmixing the block of the determined sampled audio data according to downmixing data.
An audio decoder comprising:
- one or more processors;
- and
- a non-transitory computer-readable medium,
- wherein the computer-readable medium stores decoding instructions that when executed by at least one of the processors cause carrying out a method of decoding audio data that includes encoded blocks of N.n channels of audio data to form decoded audio data that includes M.m channels of decoded audio, M≧1, n being the number of low frequency effects channels in the encoded audio data, and m being the number of low frequency effects channels in the decoded audio data, method comprising:
- accepting the audio data that includes blocks of N.n channels of encoded audio data encoded by an encoding method, the encoding method including transforming N.n channels of digital audio data, and forming and packing frequency-domain exponent and mantissa data;
- and
- decoding the accepted audio data, the decoding including:
- unpacking and decoding the frequency-domain exponent and mantissa data;
- determining transform coefficients from the unpacked and decoded frequency-domain exponent and mantissa data;
- ascertaining whether M<N,
- upon ascertaining that M<N, determining block by block whether to apply frequency-domain downmixing or time-domain downmixing, and upon determining for a particular block to apply frequency-domain downmixing, downmixing in the frequency domain according to downmixing data such that the frequency-domain data is data after downmixing;
- inverse transforming the frequency-domain data and applying further processing to determine sampled audio data;
- and
- if for the case M<N it was determined to apply time-domain downmixing, time-domain downmixing the block of the determined sampled audio data according to downmixing data.
Dependencies are inferred from the claim text.