Generating binaural audio in response to multi-channel audio using at least one feedback delay network
In some embodiments, virtualization methods for generating a binaural signal in response to channels of a multi-channel audio signal, which apply a binaural room impulse response (BRIR) to each channel including by using at least one feedback delay network (FDN) to apply a common late reverberation to a downmix of the channels. In some embodiments, input signal channels are processed in a first processing path to apply to each channel a direct response and early reflection portion of a single-channel BRIR for the channel, and the downmix of the channels is processed in a second processing path including at least one FDN which applies the common late reverberation. Typically, the common late reverberation emulates collective macro attributes of late reverberation portions of at least some of the single-channel BRIRs. Other aspects are headphone virtualizers configured to perform any embodiment of the method.
1 . A method for generating a binaural signal in response to a set of channels of a multi-channel audio input signal, the method comprising:
applying a binaural room impulse response, BRIR, to each channel of the set, thereby generating filtered signals; and
combining the filtered signals to generate the binaural signal,
wherein applying the BRIR to each channel of the set comprises using a late reverberation generator to introduce, in response to control values asserted to the late reverberation generator, a common late reverberation into a downmix of the channels of the set, wherein the common late reverberation emulates collective macro attributes of late reverberation portions of single-channel BRIRs shared across at least some channels of the set, and
wherein a content dependent energy equalization factor is applied to the downmix, and wherein a center channel of the multi-channel audio input signal is mixed to the left channel of the downmix with a coefficient of
1
2
,
and is also mixed to the right channel of the downmix with a coefficient of
1
2
.
2 . The method of claim 1 , wherein applying a BRIR to each channel of the set comprises applying to each channel of the set a direct response and early reflection portion of the single-channel BRIR for the channel.
3 . The method of claim 1 , wherein the late reverberation generator comprises a bank of feedback delay networks to apply the common late reverberation to the downmix, with each feedback delay network of the bank applying late reverberation to a different frequency band of the downmix.
4 . The method of claim 3 , wherein each of the feedback delay networks is implemented in the complex quadrature mirror filter domain.
5 . The method of claim 1 , wherein the late reverberation generator comprises a single feedback delay network to apply the common late reverberation to the downmix of the channels of the set, wherein the feedback delay network is implemented in the time domain.
6 . A system for generating a binaural signal in response to a set of channels of a multi-channel audio input signal, the system comprising one or more processors that:
apply a binaural room impulse response, BRIR, to each channel of the set, thereby generating filtered signals; and
combine the filtered signals to generate the binaural signal,
wherein applying the BRIR to each channel of the set comprises using a late reverberation generator to introduce, in response to control values asserted to the late reverberation generator, a common late reverberation into a downmix of the channels of the set, wherein the common late reverberation emulates collective macro attributes of late reverberation portions of single-channel BRIRs shared across at least some channels of the set, and
wherein a content dependent energy equalization factor is applied to the downmix, and wherein a center channel of the multi-channel audio input signal is mixed to the left channel of the downmix with a coefficient of
1
2
,
and is also mixed to the right channel of the downmix with a coefficient of
1
2
.
7 . The system of claim 6 , wherein applying a BRIR to each channel of the set comprises applying to each channel of the set a direct response and early reflection portion of the single-channel BRIR for the channel.
8 . The system of claim 6 , wherein the late reverberation generator includes a bank of feedback delay networks configured to apply the common late reverberation to the downmix, with each feedback delay network of the bank applying late reverberation to a different frequency band of the downmix.
9 . The system of claim 8 , wherein each of the feedback delay networks is implemented in the complex quadrature mirror filter domain.
10 . The system of claim 6 , wherein the late reverberation generator includes a feedback delay network implemented in the time domain, and the late reverberation generator is configured to process the downmix in the time domain in said feedback delay network to apply the common late reverberation to said downmix.
11 . A non-transitory computer readable storage medium comprising a sequence of instructions, wherein, when an audio signal processing device executes the sequence of instructions, the audio signal processing device performs the method of claim 1 .