Parametric representation of spatial audio
In summary, this application describes a psycho-acoustically motivated, parametric description of the spatial attributes of multichannel audio signals. This parametric description allows strong bitrate reductions in audio coders, since only one monaural signal has to be transmitted, combined with (quantized) parameters which describe the spatial properties of the signal. The decoder can form the original amount of audio channels by applying the spatial parameters. For near-CD-quality stereo audio, a bitrate associated with these spatial parameters of 10 kbit/s or less seems sufficient to reproduce the correct spatial impression at the receiving end.
1. A method of decoding an encoded multi-channel audio signal, the method comprising:
obtaining a monaural signal from the encoded audio signal, the monaural signal comprising a combination of at least two audio channels,
obtaining a set of spatial parameters from the encoded audio signal, and
generating a multi-channel output signal from the monaural signal and the spatial parameters, the set of spatial parameters including a parameter representing a measure of similarity of waveforms of the multi-channel output signal,
wherein the measure of similarity is a function increasing with the dissimilarity of the waveforms of the multi-channel output signal
wherein a step of obtaining a set of spatial parameters from encoded audio signal further comprises:
dividing each of the at least two audio channels into corresponding pluralities of frequency bands, and
for each of the plurality of frequency bands, determining the set of spatial parameters indicative of spatial properties of the at east two input audio channels within the corresponding frequency band,
wherein the set of spatial parameters consists of an interchannel level difference (ILD), an interchannel time or phase difference (ITD or IPD) and a dissimilarity parameter indicative of the dissimilarity of the at least two input audio channels that cannot be accounted for by the ITD, IPD or ILD,
wherein the dissimilarity parameter cannot be accounted for by the set of spatial parameters and is measured after compensation for the set of spatial parameters.
2. A decoder for decoding an encoded multi-channel audio signal, the decoder comprising
means for obtaining a monaural signal from the encoded audio signal, the monaural signal comprising a combination of at least two audio channels,
means for obtaining a set of spatial parameters from the encoded audio signal, and
means for generating a multi-channel output signal from the monaural signal and the spatial parameters, the set of spatial parameters including a parameter representing a measure of similarity of waveforms of the multi-channel output signal,
wherein the measure of similarity is a function increasing with the dissimilarity waveforms of the of the multi-channel output signal
wherein a step of obtaining a set of spatial parameters from the encoded audio signal further comprises:
dividing each of the at least audio channels into corresponding pluralities of frequency bands, and
for each of the plurality of frequency bands, determining the set of spatial parameters indicative of spatial properties of the at least two input audio channels within the corresponding frequency band
wherein the set of spatial parameters consists of an interchannel level difference (ILD), an interchannel time or phase difference (ITD or IPD), and a dissimilarity parameter indicative of the dissimilarity of the at least two input audio channels that cannot be accounted for by the ITD, IPD or ILD
wherein the dissimilarity parameter cannot be accounted for by the set of spatial parameters and is measured after compensation for the set of spatial parameters.
3. A method of decoding an encoded multi-channel audio signal, the method comprising:
obtaining a monaural signal from the encoded audio signal, the monaural signal comprising a combination of at least two audio channels,
obtaining a set of spatial parameters from the encoded audio signal, and
generating a multi-channel output signal from the monaural signal and the spatial parameters, the set of spatial parameters including a parameter representing a measure of similarity of waveforms of the multi-channel output signal, wherein the measure of similarity is a value of a cross-correlation function at a maximum of said cross-correlation function of the multi-channel output signal
wherein a step of obtaining a set of spatial parameters from the encoded audio signal further comprises:
dividing each of the at least two audio channels into corresponding pluralities of frequency bands, and
for each of the plurality of frequency bands, determining the set of spatial parameters indicative of spatial properties of the at least two input audio channels within the corresponding frequency band
wherein the set of spatial parameters consists of an interchannel level difference (ILD), an interchannel time or phase difference (ITD or IPD), and a dissimilarity parameter indicative of the dissimilarity of the at least two input audio channels that cannot be accounted for by the ITD, IPD or ILD
wherein the dissimilarity parameter cannot be accounted for by the set of spatial parameters and is measured after compensation for the set of spatial parameters.
4. A method of decoding an encoded multi-channel audio signal, the method comprising:
obtaining a monaural signal from the encoded audio signal, the monaural signal comprising a combination of at least two audio channels,
obtaining a set of spatial parameters from the encoded audio signal, and
generating a multi-channel output signal from the monaural signal and the spatial parameters,
wherein the set of spatial parameters includes at least two localization cues and a parameter representing a measure of similarity or dissimilarity of waveforms of the multi-channel output signal, and
wherein the parameter cannot be accounted for the by at least two localization cues.
5. The method of decoding as claimed in claim 4 , wherein the at least two localization cues are interchannel level difference (ILD) and interchannel time difference (ITD).
6. The method of decoding as claimed in claim 4 , wherein the parameter representing the measure of similarity of waveforms of the multi-channel output signal is the maximum interchannel cross-correlation and has a value of the normalized cross-correlation function at the position of the maximum peak.