Method for processing an audio signal in accordance with a room impulse response, signal processing unit, audio encoder, audio decoder, and binaural renderer
View Patent ↗A method for processing an audio signal in accordance with a room impulse response is described. The audio signal is separately processed with an early part and a late reverberation of the room impulse response, and the processed early part of the audio signal and the reverberated signal are combined. A transition from the early part to the late reverberation in the room impulse response is reached when a correlation measure reaches a threshold, the threshold being set dependent on the correlation measure for a selected one of the early reflections in the early part of the room impulse response.
1. A method for processing an audio signal in accordance with a room impulse response, the method comprising:
separately processing, by a processing unit, the audio signal with an early part and a late reverberation of the room impulse response; and
combining, by a processing unit, the audio signal processed with the early part of the room impulse response and a reverberated signal,
wherein a transition from the early part to the late reverberation in the room impulse response is determined once a correlation measure reaches a threshold,
wherein the correlation measure describes with regard to the room impulse response a similarity of a decay in acoustic energy comprising an initial state and of the decay in acoustic energy starting at a time following the initial state over a predefined frequency range,
wherein the threshold is set dependent on the correlation measure for a selected one of the early reflections in the early part of the room impulse response,
wherein the selected one of the early reflections is the first reflection, and
wherein the processing unit comprises a hardware implementation.
2. The method of claim 1 , wherein determining the transition comprises:
determining a distribution of acoustic energy based on the room impulse response; and;
determining a plurality of correlation measures indicating for a plurality of portions of the determined distribution a correlation between the acoustic energy in the respective portion of the determined distribution and the acoustic energy at an initial state.
3. The method of claim 2 , wherein
determining the distribution comprises determining a time-frequency distribution of the acoustic energy, and
a portion of the distribution comprises a time block of a predefined length, the initial state being defined by the first one of a plurality of time blocks of the time-frequency distribution.
4. The method of claim 3 , wherein the room impulse response comprises a predefined effective length, and wherein determining the time-frequency distribution comprises calculating the FFT spectrum of the room impulse response using a window comprising a length corresponding to the effective length of the room impulse response.
5. The method of claim 2 , wherein determining the distribution comprises calculating the energy decay relief (EDR) from the room impulse response.
6. The method of claim 5 , wherein the EDR is calculated as follows:
E ( t ,ω)=|∫ t ∞ h (τ) e −jωτ dτ| 2
where
E(t,ω)=energy decay relief at frequency f starting a time t,
h(τ)=room impulse response,
ω=2πf.
7. The method of claim 1 , wherein the correlation measure is calculated as follows:
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where
ρ(t)=correlation measure,
E(1,ω)=full frequency range energy decay relief at frequency f,
Ē(1,ω)=mean value over all frequencies of an initial full range energy decay relief,
E(t,ω)=energy decay relief at frequency f starting a time t,
Ē(t,ω)=mean value over all frequencies of the full range energy decay relief starting at time t,
ω=2πf.
8. The method of claim 1 , wherein the threshold is determined based on a constant value and the correlation measure for the selected one of the early reflections.
9. The method of claim 8 , wherein the constant is 1/e, and wherein the threshold is defined as follows:
ρ( t )= c ·ρ( t F )
where
ρ(t F )=correlation measure for the selected one of the early reflections,
t F =time index where the selected one of the early reflections after the direct sound impinges,
c=the constant value that is based on
1
e
,
e being the Euler number.
10. A non-transitory digital storage medium having computer-readable code stored thereon to perform the method of claim 1 when said storage medium is run by a computer.
11. A signal processing unit, comprising
an input for receiving an audio signal;
a processor configured to process the received audio signal in accordance with a room impulse response according to the method of claim 1 ; and
an output for combining the processed early part of the received audio signal and the reverberated signal into an output audio signal,
wherein the processor comprises a hardware implementation.
12. The signal processing unit of claim 11 , comprising:
an early part processor for processing the received audio signal in accordance with the early part of the room impulse response; and
a late reverberation processor for processing the received audio signal in accordance with the late reverberation of the room impulse response.
13. A binaural renderer, comprising the signal processing unit of claim 11 .
14. An audio encoder for encoding an audio signal, wherein
the audio encoder is configured to process an audio signal to be encoded in accordance with a room impulse response in accordance with the method of claim 1 .
15. The audio encoder of claim 14 , wherein the audio encoder comprises a signal processing unit, comprising
an input for receiving an audio signal;
a processor configured to process the received audio signal in accordance with a room impulse response; and
an output for combining the processed early part of the received audio signal and the reverberated signal into an output audio signal,
wherein the processor comprises a hardware implementation.
16. An audio decoder for decoding an encoded audio signal, wherein
the audio decoder is configured to process a decoded audio signal in accordance with a room impulse response in accordance with the method of claim 1 .
17. The audio decoder of claim 16 , wherein the audio decoder comprises a signal processing unit, comprising
an input for receiving an audio signal;
a processor configured to process the received audio signal in accordance with a room impulse response; and
an output for combining the processed early part of the received audio signal and the reverberated signal into an output audio signal,
wherein the processor comprises a hardware implementation.
18. The audio decoder of claim 16 , comprising a renderer configured to receive the decoded audio signal and to render output signals based on the room impulse response.
19. The audio decoder of claim 18 , wherein the renderer comprises a binaural renderer.