Digital audio filters for variable sample rates
View Patent ↗Various exemplary embodiments relate to a method and apparatus for processing audio signals to influence the reproduction of the audio signals. The apparatus may include a speaker, a headphone (over-the-ear, on-ear, or in-ear), a microphone, a computer, a mobile device, a home theater receiver, a television, a Blu-ray (BD) player, a compact disc (CD) player, a digital media player, or the like. The apparatus may be configured to receive a virtualization profile including a digital audio filter with a design sample rate, resample the virtualization profile to a different sample rate, filter the audio signal with the resampled virtualization profile, and reproduce the filtered audio signal as sound.
1. A method for processing an audio signal to influence the reproduction of the audio signal, comprising:
sending a request to a server computer for a virtualization profile, wherein the request specifies a requested sample rate for the virtualization profile, and wherein the virtualization profile has a design sample rate and defines a digital audio filter;
receiving from the server computer the virtualization profile with the requested sample rate;
resampling a continuous-time bandlimited impulse response (CBIR) associated with the virtualization profile at the requested sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients; and
filtering the audio signal based on at least the virtualization profile by performing a convolution of the audio signal with the virtualization profile with the requested sample rate.
2. The method of claim 1 , wherein the virtualization profile represents an acoustic model of a production environment.
3. The method of claim 1 , further comprising causing the audio signal to be reproduced as sound through an audio transducer.
4. A method for processing an audio signal to influence the reproduction of the audio signal, comprising:
requesting a virtualization profile from a server computer, wherein the virtualization profile defines a digital audio filter;
receiving from the server computer the requested virtualization profile with a design sample rate;
resampling the virtualization profile at a required sample rate for the audio signal, responsive to a difference between the required sample rate and the design sample rate, wherein resampling the virtualization profile further comprises:
interpolating the virtualization profile to obtain a representation of continuous-time bandlimited impulse response (CBIR);
resampling the CBIR at the required sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients; and
filtering the audio signal based on at least the virtualization profile with the required sample rate.
5. The method of claim 4 , wherein filtering the audio signal comprises performing a convolution of the audio signal with the virtualization profile with the required sample rate.
6. The method of claim 4 , further comprising causing the audio signal to be reproduced as sound through an audio transducer simulating a production environment.
7. A computer-implemented method for influencing reproductions of audio signals with virtualization profiles, the method comprising:
storing a virtualization profile with a design sample rate, wherein the virtualization profile defines a digital audio filter;
receiving a request for the virtualization profile from a client device, wherein the request specifies a requested sample rate for the virtualization profile;
resampling, by a computer processor, the stored virtualization profile at the requested sample rate, responsive to a difference between the requested sample rate and the design sample rate, the resampling the virtualization profile further comprising:
interpolating the virtualization profile to obtain a representation of continuous-time bandlimited impulse response (CBIR);
resampling the CBIR at the requested sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients; and
transmitting the virtualization profile with the requested sample rate to the client device.
8. The method of claim 7 , wherein the digital audio filter represents an acoustic model of a production environment comprising at least one of a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, and a feedback delay network (FDN) filter.
9. The method of claim 8 , wherein the virtualization profile causes the audio signal to be reproduced through an audio transducer simulating the production environment.
10. The method of claim 7 , wherein the virtualization profile is stored as a series of filter coefficients in fixed point or float point values.
11. The method of claim 7 , further comprising scaling the virtualization profile to a different sample rate to achieve a subjective audio effect.
12. A non-transitory computer-readable storage medium storing computer-executable instructions that when executed cause one or more processors to perform operations comprising:
storing a virtualization profile with a design sample rate, wherein the virtualization profile defines a digital audio filter;
receiving a request for the virtualization profile from a client device, wherein the request specifies a requested sample rate for the virtualization profile;
resampling the stored virtualization profile at the requested sample rate, responsive to a difference between the requested sample rate and the design sample rate, wherein resampling the virtualization profile further comprises:
interpolating the virtualization profile to obtain a representation of continuous-time bandlimited impulse response (CBIR);
resampling the CBIR at the requested sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients; and
transmitting the virtualization profile with the requested sample rate to the client device.
13. The non-transitory computer-readable storage medium of claim 12 , wherein the digital audio filter represents an acoustic model of a production environment comprising at least one of a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, and a feedback delay network (FDN) filter.
14. The non-transitory computer-readable storage medium of claim 13 , wherein the virtualization profile causes the audio signal to be reproduced through an audio transducer simulating the production environment.
15. An audio device for processing an audio signal, comprising:
a communication interface configured for:
sending a request to a server computer for a virtualization profile, wherein the request specifies a requested sample rate for the virtualization profile, and wherein the virtualization profile defines a digital audio filter simulating a virtualized environment; and
receiving from the server computer the requested virtualization profile with the requested sample rate;
a storage device for storing the received virtualization profile; and
a processor in communication with the storage device and the communication interface, the processor programmed for:
resampling a continuous-time bandlimited impulse response (CBIR) associated with the virtualization profile at the requested sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients;
filtering the audio signal based on at least the virtualization profile by performing a convolution of the audio signal with the virtualization profile with the requested sample rate.
16. An audio device for processing an audio signal, comprising:
a communication interface configured for:
requesting a virtualization profile from a server computer, wherein the virtualization profile defines a digital audio filter simulating a virtualized environment; and
receiving from the server computer the requested virtualization profile with a design sample rate;
a storage device for storing the received virtualization profile; and
a processor in communication with the storage device and the communication interface, the processor programmed for:
resampling the virtualization profile at a required sample rate for the audio signal, responsive to a difference between the required sample rate and the design sample rate, wherein resampling the virtualization profile further comprises:
interpolating the virtualization profile to obtain a representation of continuous-time bandlimited impulse response (CBIR);
resampling the CBIR at the required sample rate, wherein resampling the CBIR at a lower sample rate than the design sample rate results in fewer filter coefficients and wherein resampling the CBIR at a higher sample rate than the design sample rate results in more filter coefficients; and
filtering the audio signal based on at least the virtualization profile with the required sample rate.
17. The audio device of claim 16 , wherein filtering the audio signal comprises performing a convolution of the audio signal with the virtualization profile at the required sample rate.