Adjusting a data rate of a digital audio stream based on dynamically determined audio playback system capabilities

Patent metadata

Field	Value
Publication number	US-9286904-B2
Application number	US-201213412987-A
Country	US
Kind code	B2
Filing date	Mar 6, 2012
Priority date	Mar 6, 2012
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

A computing device may be configured to output a digital audio stream to an audio playback system for rendering as sound over speakers. The sound may be sampled. Based at least in part on a quality of the sampled sound, the data rate of the digital audio stream may be reduced by reducing a sampling rate and/or by reducing a number of bits per sample. A reduced sampling rate may be determined based on a computed maximum sampling rate of the audio playback system, and/or a reduced number of bits per sample may be determined based on a computed maximum number of bits per sample of the audio playback system. The maximum usable sampling rate and maximum usable number of bits per sample may be determined based on an upper usable frequency within a frequency spectrum of the sampled sound.

First claim

What is claimed is:

1. A method of adjusting a data rate of a digital audio stream, the method comprising:
sampling sound generated, from a digital audio stream, by an audio playback system;
ascertaining, from the sampled sound, a sound quality of the generated sound; and
based at least in part on the ascertained sound quality of the generated sound, reducing the data rate of the digital audio stream by performing either one or both of:
reducing a sampling rate of the digital audio stream to a reduced sampling rate; and
reducing a number of bits per sample of the digital audio stream to a reduced number of bits per sample.

2. The method of claim 1 , further comprising:
identifying a frequency above which amplitude distortion of the sampled sound exceeds a predetermined amplitude distortion limit and phase distortion of the sampled sound exceeds a predetermined phase distortion limit, the identified frequency being referred to as an upper usable frequency; and
computing, based on the upper usable frequency, a maximum usable sampling rate of the audio playback system,
wherein the reduced sampling rate is determined on the basis of the computed maximum usable sampling rate.

3. The method of claim 2 wherein the determining of the upper usable frequency comprises:
transforming the sampled sound from a time domain to a frequency domain, the transforming resulting in the frequency spectrum of the sampled sound, the frequency spectrum comprising a frequency component in each of a plurality of frequency bins, the transforming yielding amplitude information and phase information regarding each of the frequency components; and
using the amplitude and phase information regarding each of the frequency components, determining, for each of the frequency components of the frequency spectrum, an amplitude distortion and a phase distortion.

4. The method of claim 2 wherein the computing of the maximum usable sampling rate comprises setting the maximum usable sampling rate to twice the upper usable frequency.

5. The method of claim 2 further comprising determining the reduced sampling rate of the digital audio stream by rounding the maximum usable sampling rate of the audio playback system down to a closest standard sampling rate.

6. The method of claim 2 further comprising determining the reduced sampling rate of the digital audio stream by rounding the maximum usable sampling rate up to a closest standard sampling rate.

7. The method of claim 1 , further comprising:
identifying a frequency above which amplitude distortion of the sampled sound exceeds a predetermined amplitude distortion limit and phase distortion of the sampled sound exceeds a predetermined phase distortion limit, the identified frequency being referred to as an upper usable frequency; and
computing, based on a portion of a frequency spectrum of the sampled sound at or below the upper usable frequency, a maximum usable number of bits per sample of the audio playback system,
wherein the reduced number of bits per sample is determined on the basis of the computed maximum usable number of bits per sample.

8. The method of claim 7 wherein the determining of the upper usable frequency comprises:
transforming the sampled sound from a time domain to a frequency domain, the transforming resulting in the frequency spectrum of the sampled sound, the frequency spectrum comprising a frequency component in each of a plurality of frequency bins, the transforming yielding amplitude information and phase information regarding each of the frequency components; and
using the amplitude and phase information regarding each of the frequency components, determining, for each of the frequency components of the frequency spectrum, an amplitude distortion and a phase distortion.

9. The method of claim 7 wherein the computing of a maximum usable number of bits per sample of the audio playback system comprises:
measuring a total harmonic distortion and noise (THD+N) of the portion of the spectrum at or below the upper usable frequency; and
converting the THD+N measurement to the maximum usable number of bits per sample.

10. The method of claim 7 further comprising determining the reduced number of bits per sample of the digital audio stream either by rounding the maximum usable number of bits per sample down to a closest standard number of bits per sample or by rounding the maximum usable number of bits per sample up to a closest standard number of bits per sample.

11. The method of claim 1 wherein the digital audio stream comprises uncompressed audio data or audio data that has been compressed using a lossless compression format.

12. A computing device configured for outputting a digital audio stream to an audio playback system for rendering as sound over speakers, the computing device comprising a processor, the processor operable to adjust a data rate of the digital audio stream by:
sampling the sound generated, from the digital audio stream, by the audio playback system;
ascertaining, from the sampling, a sound quality of the generated sound; and
based at least in part on the ascertained sound quality of the generated sound, reducing the data rate of the digital audio stream by performing either one or both of:
reducing a sampling rate of the digital audio stream to a reduced sampling rate; and
reducing a number of bits per sample of the digital audio stream to a reduced number of bits per sample.

13. The computing device of claim 12 wherein the processor is further operable to:
identify a frequency above which amplitude distortion of the generated sound exceeds a predetermined amplitude distortion limit and phase distortion of the generated sound exceeds a predetermined phase distortion limit, the identified frequency being referred to as an upper usable frequency; and
compute, based on the upper usable frequency, a maximum usable sampling rate of the audio playback system,
wherein the reduced sampling rate is determined on the basis of the computed maximum usable sampling rate.

14. The computing device of claim 13 wherein the processor is further operable to determine the reduced sampling rate of the digital audio stream either by rounding the maximum usable sampling rate of the audio playback system down to a closest standard sampling rate or by rounding the maximum usable sampling rate up to a closest standard sampling rate.

15. The computing device of claim 12 wherein the processor is further operable to:
identify a frequency above which amplitude distortion of the generated sound exceeds a predetermined amplitude distortion limit and phase distortion of the generated sound exceeds a predetermined phase distortion limit, the identified frequency being referred to as an upper usable frequency; and
compute, based on a portion of a frequency spectrum of the generated sound at or below the upper usable frequency, a maximum usable number of bits per sample of the audio playback system,
wherein the reduced number of bits per sample is determined on the basis of the computed maximum usable number of bits per sample.

16. The computing device of claim 15 wherein the processor is further operable to determine the reduced number of bits per sample of the digital audio stream either by rounding the maximum usable number of bits per sample down to a closest standard number of bits per sample or by rounding the maximum usable number of bits per sample up to a closest standard number of bits per sample.

17. A non-transitory tangible machine-readable medium storing instructions that, upon execution by a processo

Assignees

• Wakeland Carl
• Herz William
• Ati Technologies Ulc

Inventors

• Wakeland Carl
• Herz William

Classifications

• G10L19/24 Primary

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title

• G10L19/002

  Dynamic bit allocation (for perceptual audio coders G10L19/032) · CPC title