Reconstruction of audio scenes from a downmix
Audio objects are associated with positional metadata. A received downmix signal comprises downmix channels that are linear combinations of one or more audio objects and are associated with respective positional locators. In a first aspect, the downmix signal, the positional metadata and frequency-dependent object gains are received. An audio object is reconstructed by applying the object gain to an upmix of the downmix signal in accordance with coefficients based on the positional metadata and the positional locators. In a second aspect, audio objects have been encoded together with at least one bed channel positioned at a positional locator of a corresponding downmix channel. The decoding system receives the downmix signal and the positional metadata of the audio objects. A bed channel is reconstructed by suppressing the content representing audio objects from the corresponding downmix channel on the basis of the positional locator of the corresponding downmix channel.
1. A method for reconstructing a time frame of an audio scene with at least a plurality of N audio signals from a bitstream, the method comprising:
Extracting, for each of the N audio signals, positional metadata associated with each audio signal, wherein N>1;
decoding a downmix signal from the bitstream, the downmix signal comprising M downmix channels, wherein M>1 and each downmix channel is associated with a spatial locator of a plurality of spatial locators; and
reconstructing at least one of the N audio signals as an inner product of a plurality of correlation coefficients and the downmix signal, wherein the plurality of correlation coefficients is computed based on the positional metadata for the N audio signals and the plurality of spatial locators of the M downmix channels.
2. The method of claim 1 , wherein at least one of the N audio signals is reconstructed independently for each frequency band.
3. The method of claim 1 , further comprising obtaining the spatial locator of at least one of the M downmix channels from a source that is different from the bitstream.
4. The method of claim 1 , further comprising scaling the inner product using a gain specific to the corresponding audio signal.
5. The method of claim 1 , wherein the plurality of correlation coefficient are computed using a panning law related to audio source positioning.
6. An audio decoding system configured to reconstruct a time frame of an audio scene with at least a plurality of N audio signals from a bitstream, the system comprising:
a metadata decoder for extracting, for each of the N audio signals, positional metadata associated with each audio signal, wherein N>1;
a downmix decoder for decoding a downmix signal from the bitstream, the downmix signal comprising M downmix channels, wherein M>1 and each downmix channel is associated with a spatial locator of a plurality of spatial locators; and
an upmixer configured to:
reconstruct at least one of the N audio signals as an inner product of a plurality of correlation coefficients and the downmix signal, wherein the plurality of correlation coefficients is computed based on the positional metadata for the N audio signals and the plurality of spatial locators of the M downmix channels.
7. The system of claim 6 , wherein at least one of the N audio signals is reconstructed independently for each frequency band.
8. The audio decoding system of claim 6 , wherein the downmix decoder is configured to obtain the spatial locator of at least one of the M downmix channels from a source that is different from the bitstream.
9. The audio decoding system of claim 6 , wherein the upmixer is configured to scale the inner product using a gain specific to the corresponding audio signal.
10. The audio decoding system of claim 6 , wherein the plurality of correlation coefficient are computed using a panning law.
11. A computer program product comprising a non-transitory computer-readable medium encoded with instructions configured to cause one or more processing devices to perform operations comprising:
extracting, for each of N audio signals, positional metadata associated with each audio signal, wherein N>1;
decoding a downmix signal from the bitstream, the downmix signal comprising M downmix channels, wherein M>1 and each downmix channel is associated with a spatial locator of a plurality of spatial locators; and
reconstructing at least one of the N audio signals as an inner product of a plurality of correlation coefficients and the downmix signal, wherein the plurality of correlation coefficients is computed based on the positional metadata for the N audio signals and the plurality of spatial locators of the M downmix channels.