Audio content enhancement using bandwidth extension techniques
Methods, devices and computer program products facilitate the generation of high quality audio content. The audio content includes upper harmonics that are associated with a bass band of frequencies in order to enhance the perception of bass audio components that cannot be produced by the audio speakers. The upper harmonics are generated and processed in such a way that reduces the computational and memory requirements of the audio processing operations. The processed upper harmonics are combined with the original audio that are properly delayed to enhance the quality of the audio content. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the disclosed subject matter. Therefore, it is to be understood that it should not be used to interpret or limit the scope or the meaning of the claims.
1. A method, comprising:
receiving, via a communication link, an input audio content;
performing by a processor a wet chain processing on the input audio content, the wet chain processing comprising:
isolating by filtering, by the processor, a first band of frequencies to be compensated, from the input audio content;
producing by the processor from the isolated first frequency band upper harmonics of the frequencies to be compensated and in the first frequency band of the input audio content, the upper harmonics being located in a second frequency band; and
filtering by the processor the upper harmonics using an infinite impulse response bandpass filter to produce a wet chain audio component;
determining by the processor: (i) a stage one group delay corresponding to the first frequency band, and (ii) a stage two group delay corresponding to the second frequency band;
performing by the processor a dry chain processing on the input audio content, the dry chain processing comprising:
generating by the processor an aggregated dry chain group delay to match a wet chain group delay associated with the infinite impulse response bandpass filter, the aggregated dry chain group delay being based on, at least in part, both the stage one and stage two group delays; and
applying by the processor the aggregated dry chain group delay to the input audio content to produce a dry chain audio component; and
combining by the processor the wet chain audio component with the dry chain audio component,
at least one of the first band of frequencies, the upper harmonics, the wet chain audio component, the stage one and stage two group delays, the aggregated dry chain group delay, and the dry chain component being stored in a memory coupled to the processor.
2. The method of claim 1 , wherein the dry chain group delay is generated using at least one all-pass filter to produce a group delay in the second band of frequencies that matches the group delay associated with the infinite impulse response bandpass filter.
3. The method of claim 2 , wherein
each all-pass filter is a second-order all-pass filter; and
each all pass filter is configured to exhibit a particular group delay characteristic in a sub-band of frequencies within the second band of frequencies.
4. The method of claim 1 , wherein the wet chain processing comprises filtering the input audio content to produce the first band of frequencies.
5. The method of claim 4 , wherein the first band of frequencies is produced using a first infinite impulse response filter.
6. The method of claim 5 , wherein the dry chain processing comprises generating the dry chain group delay by matching a wet chain group delay associated with the first infinite impulse response bandpass filter.
7. The method of claim 1 , wherein the wet chain processing comprises spectral shaping an output of the infinite impulse response bandpass filter to produce the wet chain audio component.
8. The method of claim 7 , wherein the spectral shaping is carried out using a parametric filter.
9. The method of claim 8 , wherein the parametric filter is configured to emphasize a lower sub-band of frequencies within the second band of frequencies.
10. The method of claim 1 , wherein the wet chain processing comprises generating and applying an offset delay to a signal based on the infinite impulse response bandpass filter output to produce the wet chain audio component prior to the combining thereof with the dry chain component, the offset delay representing a difference between the aggregated dry-chain group delay corresponding to the first frequency band and a wet-chain group delay corresponding to the first frequency band.
11. The method of claim 1 , wherein the wet chain processing comprises generating and applying a gain to a signal based on the infinite impulse response bandpass filter output to produce the wet chain audio component prior, to the combining thereof with the dry chain audio component.
12. The method of claim 1 , wherein the dry chain processing comprises generating and applying a gain to an output of a delay compensator to produce the dry chain audio component, prior to the combining thereof with the wet chain audio component.
13. The method of claim 1 , wherein
the input audio content is a single-channel audio content; and
the dry chain processing and wet chain processing are carried out on the single-channel audio content.
14. The method of claim 1 , wherein
the input audio content is a multi-channel audio content;
the dry chain processing and wet chain processing are carried out on individual channels of the multi-channel audio content; and
combining the wet chain audio component with the dry chain audio component comprises combining each processed dry chain individual channel with respective processed wet chain individual channel.
15. The method of claim 1 , wherein
the input audio content is a multi-channel audio content;
the dry chain processing is carried out on individual channels of the multi-channel audio content;
at least a portion of the wet chain processing is carried out on a combined audio content that comprises two or more of the channels of the multi-channel audio content to produce the wet chain audio component; and
combining the wet chain audio component with the dry chain audio component comprises combining each processed dry chain individual channel with the wet chain audio component.
16. A device, comprising:
a processor; and
a memory, comprising processor executable code, the processor executable code, when executed by the processor, configures the device to:
receive, via a communication link, an input audio content;
perform a wet chain processing on the input audio content by configuring the device to:
isolate by filtering, a first band of frequencies to be compensated, from the input audio content;
produce from the isolated first frequency band upper harmonics of the frequencies to be compensated and in the first frequency band of the input audio content, the upper harmonics being located in a second frequency band; and
filter the upper harmonics using an infinite impulse response bandpass filter to produce a wet chain audio component;
determine: (i) a stage one group delay corresponding to the first frequency band, and (ii) a stage two group delay corresponding to the second frequency band;
perform a dry chain processing on the input audio content by configuring the device to:
generate an aggregated dry chain group delay to match a wet chain group delay associated with the infinite impulse response bandpass filter, the aggregated dry chain group delay being based on, at least in part, both the stage one and stage two group delays; and
apply the aggregated dry chain group delay to the input audio content to produce a dry chain audio component; and
combine the wet chain audio component with the dry chain audio component,
at least one of the first band of frequencies, the upper harmonics, the wet chain audio component, the stage one and stage two group delays, the aggregated dry chain group delay, and the dry chain component being stored in the memory.
17. The device of claim 16 , wherein the dry chain group delay is generated using at least one all-pass filter configured to produce a group delay in the second band of frequencies that matches the group delay associated with the infinite impulse response bandpass filter.
18. The device of claim 17 , wherein
each all-pass filter is a second-order all-pass filter; and
each all pass filter is configured to exhibit a particular group delay characteristic in a sub-band of frequencies within the second band of frequencies.
19. The device of claim 16 , wherein, as part of the wet chain processing, the processor executable code, when executed by the processor, configures the device to filter the input audio content to produce the first band of frequencies.
20. The device of claim 19 , wherein the first band of frequencies is produced by a first infinite impulse response filter.
21. The device of claim 20 , wherein, as part of the dry chain processing, the processor executable code, when executed by the processor, configures the device to generate the dry chain group delay by matching a wet chain group delay associated with the first infinite impulse response bandpass filter.
22. The device of claim 16 , wherein, as part of the wet chain processing, the processor executable code, when executed by the processor, configures the device to spectrally shape an output of the infinite impulse response bandpass filter to produce the wet chain audio component.
23. The device of claim 22 , wherein a parametric filter is used to carry out the spectral shaping.
24. The device of claim 23 , wherein the parametric filter is configured to emphasize a lower sub-band of frequencies within the second band of frequencies.
25. The device of claim 16 , wherein, as part of the wet chain processing, the processor executable code, when executed by the processor, configures the device to generate and apply an offset delay to a signal based on the infinite impulse response bandpass filter output to produce the wet chain audio component, prior to the combination thereof with the dry chain audio component, the offset delay representing a difference between the aggregated dry-chain group delay corresponding to the first frequency band and a wet-chain group delay corresponding to the first frequency band.
26. The device of claim 16 , wherein, as part of the wet chain processing, the processor executable code, when executed by the processor, configures the device to generate and apply a gain to a signal based on the infinite impulse response bandpass filter output to produce the wet chain audio component prior to the combination thereof with the dry chain audio component.
27. The device of claim 16 , wherein, as part of the dry chain processing, the processor executable code, when executed by the processor, configures the device to generate and apply a gain to an output of a delay compensator to produce the dry chain audio component, prior to the to the combination thereof with the wet chain audio component.
28. The device of claim 16 , wherein
the input audio content is a single-channel audio content; and
the processor executable code, when executed by the processor, configures the device the device to carry out the dry chain processing and wet chain processing on the single-channel audio content.
29. The device of claim 16 , wherein
the input audio content is a multi-channel audio content;
the processor executable code, when executed by the processor, configures the device the device to carry out the dry chain processing and the wet chain processing on individual channels of the multi-channel audio content; and
the combination of the wet chain audio component with the dry chain audio component comprises a combination of each processed dry chain individual channel with respective processed wet chain individual channel.
30. The device of claim 16 , wherein
the input audio content is a multi-channel audio content; and
the processor executable code, when executed by the processor, configures the device the device to carry out the dry chain processing on individual channels of the multi-channel audio content, and at least a portion of the wet chain processing on a combined audio content that comprises two or more of the channels of the multi-channel audio content to produce the wet chain audio component; and
the combination of the wet chain audio component with the dry chain audio component comprises a combination of each processed dry chain individual channel with the wet chain audio component.
31. A computer program product, embodied on a non-transitory computer readable medium, comprising:
computer code for receiving, via a communication link, an input audio content;
computer code for performing a wet chain processing on the input audio content, the wet chain processing comprising:
isolating by filtering, a first band of frequencies to be compensated, from the input audio content;
producing from the isolated first frequency band upper harmonics of the frequencies to be compensated and in the first frequency band of the input audio content, the upper harmonics being located in a second frequency band; and
filtering the upper harmonics using an infinite impulse response bandpass filter to produce a wet chain audio component;
computer code for determining: (i) a stage one group delay corresponding to the first frequency band, and (ii) a stage two group delay corresponding to the second frequency band;
computer code for performing a dry chain processing on the input audio content, the dry chain processing comprising:
generating a dry chain group delay to match a wet chain group delay associated with the infinite impulse response bandpass filter, the aggregated dry chain group delay being based on, at least in part, both the stage one and stage two group delays; and
applying the aggregated dry chain group delay to the input audio content to produce a dry chain audio component;
computer code for combining the wet chain audio component with the dry chain audio component; and
computer code for storing at least one of the first band of frequencies, the upper harmonics, the wet chain audio component, the stage one and stage two group delays, the aggregated dry chain group delay, and the dry chain component in a memory.
32. The computer program product of claim 31 , wherein the dry chain group delay is generated using at least one all-pass filter to produce a group delay in the second band of frequencies that matches the group delay associated with the infinite impulse response bandpass filter.
33. The computer program product of claim 32 , wherein each all-pass filter is a second-order all-pass filter; and
each all pass filter is configured to exhibit a particular group delay characteristic in a sub-band of frequencies within the second band of frequencies.
34. The computer program product of claim 31 , wherein the wet chain processing comprises filtering the input audio content to produce the first band of frequencies.
35. The computer program product of claim 34 , wherein the first band of frequencies is produced using a first infinite impulse response filter.
36. The computer program product of claim 35 , wherein the dry chain processing comprises generating the dry chain group delay by matching a wet chain group delay associated with the first infinite impulse response bandpass filter.