Encoding of a multi-channel audio signal to generate binaural signal and decoding of an encoded binauralsignal
An audio encoder comprises a multi-channel receiver which receives an M-channel audio signal where M>2. A down-mix processor down-mixes the M-channel audio signal to a first stereo signal and associated parametric data and a spatial processor modifies the first stereo signal to generate a second stereo signal in response to the associated parametric data and spatial parameter data for a binaural perceptual transfer function, such as a Head Related Transfer Function (HRTF). The second stereo signal is a binaural signal and may specifically be a (3D) virtual spatial signal. An output data stream comprising the encoded data and the associated parametric data is generated by an encode processor and an output processor. The HRTF processing may allow the generation of a (3D) virtual spatial signal by conventional stereo decoders. A multi-channel decoder may reverse the process of the spatial processor to generate an improved quality multi-channel signal.
1. An audio decoder, comprising:
a receiver circuit, wherein the receiver circuit is configured to receive a three-dimensional binaural signal and down-mixed associated parametric data, wherein the down-mixed associated parametric data is associated with a down-mixed stereo signal of a plurality of audio signals of a corresponding plurality of audio channels, wherein the audio channels are spatially diverse, and wherein the three-dimensional binaural signal emulates one sound source position in three dimensions for each of the plurality of audio channels; and
a processor circuit, wherein the processor circuit is configured to generate the down-mixed stereo signal by applying a reverse binaural perceptual transfer function and the down-mixed associated parametric data to the received three-dimensional binaural signal, and wherein the processor circuit is configured to generate the plurality of audio signals in response to the down-mixed stereo signal and the down-mixed associated parametric data,
wherein the processor circuit is configured to receive sound source position data,
wherein the processor circuit is configured to determine first spatial parameter data in response to the sound source position data, and
wherein the decoder further comprises a spatial decoder circuit, wherein the spatial decoder circuit is configured to produce a pair of binaural output channels by modifying the three-dimensional binaural signal in response to the down-mixed associated parametric data and in response to second spatial parameter data associated with a second binaural perceptual transfer function, wherein the second spatial parameter data is different than the first spatial parameter data.
2. The decoder of claim 1 , wherein the spatial decoder circuit comprises:
a parameter converter circuit, wherein the parameter converter circuit is configured to convert the down-mixed associated parametric data into binaural synthesis parameters using the second spatial parameter data; and
a spatial synthesizer circuit, wherein the spatial synthesizer circuit is configured to synthesize the pair of binaural output channels using the binaural synthesis parameters and the received three-dimensional binaural signal.