CORRECTION OF UNKNOWN AUDIO CONTENT

• US 20170207762A1
• Filed: 01/19/2016
• Published: 07/20/2017
• Est. Priority Date: 01/19/2016
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Porter, Simon K., Family, Afrooz, Johnson, Martin E., Powell, Richard M.
• Granted Patent: US 9,859,858 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path
• CPC Class Codes: G10L 25/03 characterised by the type of extracted parameters
• CPC Class Codes: G10L 25/48 specially adapted for particular use
• CPC Class Codes: G10L 25/54 for retrieval
• CPC Class Codes: H03G 3/002 Control of digital or coded signals H03G3/3089 take precedence
• CPC Class Codes: H03G 3/3005 in amplifiers suitable for low-frequencies, e.g. audio amplifiers H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03G 3/3089 Control of digital or coded signals
• CPC Class Codes: H03G 5/005 of digital signals
• CPC Class Codes: H03G 5/16 Automatic control
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 7/002 in untuned or low-frequency amplifiers, e.g. audio amplifiers H03G7/007, H03G7/001, H03G7/008, H03G7/02, H03G7/06 take precedence
• CPC Class Codes: H03G 7/007 of digital or coded signals
• CPC Class Codes: H03G 9/005 of digital or coded signals
• CPC Class Codes: H04R 2430/01 Aspects of volume control, not necessarily automatic, in sound systems
• CPC Class Codes: H04R 3/007 Protection circuits for transducers
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

An unknown content audio signal that is input to an audio power amplifier and speaker that have a known gain and speaker sensitivity, is buffered. A portion of the buffered signal is provided to an automatic content recognition (ACR) system, and then a content identifier, of the unknown content signal, as provided by the ACR system is received. Previously determined metadata is also received, for a reference audio content signal that has been assigned to the content identifier. The metadata includes a previously determined reference measure of an audio signal characteristic for the reference content. An input measure of the audio signal characteristic is computed, for the unknown content, and compared with the reference measure. On that basis, and also based on the known gain and speaker sensitivity, at least one of a scalar gain and spectral shaping filtering that is being applied to the unknown content is adjusted. Other embodiments are also described and claimed.

Claims

1. A method for correcting unknown audio content to suit an audio power amplifier and speaker, comprising:

buffering an unknown content audio signal that is to be input to an audio power amplifier and speaker, and wherein the audio power amplifier and speaker have a known gain and speaker sensitivity;

providing a portion of the buffered, unknown content audio signal to an automatic content recognition (ACR) system, and then receiving a content identifier, for the portion of the unknown content audio signal, as provided by the ACR system;

receiving previously determined metadata for a reference audio content signal that has been assigned to the content identifier, wherein the metadata includes a previously determined reference measure of an audio signal characteristic for the reference audio content signal;

computing an input measure of the audio signal characteristic, for the unknown content audio signal;

comparing the input measure with the reference measure;

based on i) comparing the input measure with the reference measure and ii) the known gain and speaker sensitivity, adjusting at least one of a scalar gain and spectral shaping filtering; and

applying the scalar gain and the spectral shaping filtering to the unknown content audio signal.

2. The method of claim 1 wherein the unknown content audio signal reflects the application of a scalar gain that is in accordance with a user volume setting for playback through the audio power amplifier and speaker, and wherein said adjusting at least one of a scalar gain and spectral shaping filtering is further based on the user volume setting.

3. The method of claim 1 wherein the audio signal characteristic is scaling factor, and wherein said adjusting at least one of a scalar gain and spectral shaping filtering comprises adjusting the scalar gain and not the spectral shaping filtering.

4. The method of claim 1 wherein the previously determined metadata includes a reference measure of program loudness or loudness per time frame or recording level, for the reference audio content signal, the method further comprising:

computing an input measure of program loudness or loudness per time frame or level, for the unknown content audio signal;

comparing the input measure with the reference measure;

based on comparing the input measure with the reference measure, adjusting at least one of the scalar gain and the spectral shaping filtering.

5. The method of claim 1 wherein the previously determined metadata for the reference audio content signal includes reference measures of crest factor and scaling factor for the reference audio content signal, the method further comprising:

computing input measures of crest factor and scaling factor for the unknown content signal;

calculating an input measure of perceptual loudness or level using i) the input measures of crest factor and scaling factor, and ii) the known gain and speaker sensitivity of the audio power amplifier and speaker;

one of a) calculating a reference measure of perceptual loudness or level, using i) the reference measures of crest factor and scaling factor, and ii) the known gain and speaker sensitivity of the audio power amplifier and speaker, or b) obtaining the reference measure of perceptual loudness or level via lookup in the metadata;

based on the perceptual loudness or level calculations, adjusting at least one of the scalar gain, the spectral shaping filtering, and dynamic range control (DRC) setting; and

applying the scalar gain and the spectral shaping filtering to the unknown audio content signal, and altering dynamic range of the unknown content audio signal in accordance with the DRC setting.

6. The method of claim 1 further comprising

receiving the reference audio content signal;

computing a reference measure of a spectral content in the reference audio content signal;

computing an input measure of the spectral content in the unknown content signal;

comparing the reference measure of the spectral content with the input measure of the spectral content; and

based on comparing the reference and input measures of the spectral content, adjusting the spectral shaping filtering.

7. The method of claim 1 further comprising

receiving the reference audio content signal;

computing a reference measure of a perceptual loudness or an rms level from the reference audio content signal;

computing an input measure of the perceptual loudness or the rms level from the unknown content signal;

comparing the reference measure of the perceptual loudness or the rms level with the input measure of the perceptual loudness or the rms level; and

based on comparing the reference and input measures of the perceptual loudness or the rms level, adjusting a dynamic range control (DRC) setting that is applied to alter dynamic range of the unknown content audio signal.

8. The method of claim 1 further comprising

measuring sound playback level of the unknown content audio signal, as it is being input to the audio power amplifier and speaker,

wherein adjusting at least one of scalar gain and spectral shaping filtering is further based on the measured sound playback level.

9. A process for correcting unknown content audio to suit an audio power amplifier and speaker, comprising:

buffering an unknown content audio signal that is to be input to an audio power amplifier and speaker, and wherein the audio power amplifier and speaker have a known gain and speaker sensitivity;

providing a portion of the buffered, unknown content audio signal to an automatic content recognition (ACR) system, and then receiving a content identifier for the portion of the unknown content audio signal, as provided by the ACR system;

receiving a reference audio content signal that has been assigned to the content identifier;

performing time domain or spectral analysis upon the reference audio content signal to detect a predetermined sound event in the reference audio content signal;

calculating a correction value based on the detected sound event and based on the known gain and speaker sensitivity; and

applying scalar gain and spectral shaping filtering to the unknown audio content signal, wherein at least one of the applied scalar gain and spectral shaping filtering has been adjusted in accordance with the correction value.

10. The process of claim 9 wherein receiving the content identifier of the unknown content audio signal and receiving the reference audio content signal comprises receiving them via a communications transceiver from one or more remote nodes of the Internet, in response to having transmitted, also via the communications transceiver, the portion of the buffered unknown content audio signal to the ACR system in a remote node of the Internet.

11. An audio signal processing and playback system comprising:

means for applying scalar gain to a user content audio signal;

means for shaping a frequency band of the user content audio signal;

an audio power amplifier and speaker to receive the user content audio signal, downstream of the means for applying scalar gain and the means for shaping the frequency band, for playback;

means for buffering the user content audio signal, upstream of the means for applying scalar gain and the means for shaping the frequency band;

means for providing a portion of the buffered user content audio signal to an ACR system, receiving a content identifier, for said portion of the user content audio signal, as provided by the ACR system, and receiving previously determined metadata for a reference content audio signal that has been assigned to the content identifier, wherein the metadata includes a previously determined reference measure of an audio signal characteristic for the reference content audio signal;

means for computing an input measure of the audio signal characteristic, for the user content audio signal;

means for comparing the input measure with the reference measure; and

means for producing a correction value based on i) comparing the input measure with the reference measure, and ii) gain and speaker sensitivity of the audio power amplifier and speaker, wherein the correction value adjusts at least one of said means for applying scalar gain and means for shaping a frequency band.

12. The system of claim 11 wherein the received metadata includes a reference measure of program loudness or loudness per time frame or level, the system further comprising:

means for controlling a dynamic range of the user content audio signal;

means for computing an input measure of program loudness or loudness per time frame or level, for the user content audio signal;

means for comparing the input and reference measures, of program loudness or loudness per time frame or level; and

means for producing a correction value based on i) comparing the input and reference measures, of program loudness or loudness per time frame or level, and ii) gain and speaker sensitivity of the audio power amplifier and speaker, wherein the correction value adjusts at least one of said means for applying scalar gain and means for shaping a frequency band and means for controlling dynamic range.

13. The system of claim 11 wherein the audio signal characteristic is crest factor.

16. The article of manufacture of claim 11 wherein the audio signal characteristic is crest factor.

14. An article of manufacture, comprising:

a machine readable medium having stored therein instructions that when executed by a processor,

provide a portion of a user content signal that is to be input to an audio power amplifier and speaker for playback, to an ACR system and then receive a content identifier, of the user content signal, as provided by the ACR system,

receive previously determined metadata for a reference audio content signal that has been assigned to the content identifier, wherein the metadata includes a previously determined reference measure of an audio signal characteristic for the reference audio content signal,

compute an input measure of the audio signal characteristic, for the user content signal,

compare the input measure with the reference measure, and

adjust at least one of a scalar gain, spectral shaping filtering, and a dynamic range control setting that is to be applied to the user content signal during playback through the audio power amplifier and speaker, wherein the adjustment is based on i) having compared the input measure with the reference measure, ii) a user volume setting for said playback, and iii) gain and speaker sensitivity of the audio power amplifier and speaker.

15. The article of manufacture of claim 14 wherein the machine readable medium has stored therein instructions that when executed by the processor compute the input measure of the audio signal characteristic as being an input measure of program loudness or rms level, and the reference measure of the audio signal characteristic as being a reference measure of program loudness or rms level,

and wherein when the input measure of program loudness or rms level is larger than the reference measure of program loudness or rms level by at least a threshold, the adjusting of the at least one of the scalar gain, spectral shaping filtering, and dynamic range control setting comprises one of a) reducing the scalar gain, b) reducing gain in a particular frequency band during the spectral shaping filtering, or c) increasing a dynamic range compression ratio.

17. An audio signal processing system comprising:

a processor; and

memory having stored therein instructions that when executed by the processor

cause a portion of a user content signal, that is to be input to an audio power amplifier that is to drive a signal input of a speaker for playback, to be sent to an ACR system and then receive a content identifier, of the user content signal, as provided by the ACR system,

receive previously determined metadata for a reference audio content signal that has been assigned to the content identifier, wherein the metadata includes a previously determined reference measure of an audio signal characteristic for the reference audio content signal,

compute an input measure of the audio signal characteristic, for the user content signal,

compare the input measure with the reference measure, and

adjust at least one of a scalar gain, spectral shaping filtering, and a dynamic range control setting that is being applied to the user content signal during the playback through the audio power amplifier and speaker, wherein the adjustment is based on i) having compared the input measure with the reference measure, ii) a user volume setting for said playback, and iii) gain and speaker sensitivity of the audio power amplifier and speaker.

18. The system of claim 17 wherein the audio signal characteristic is program loudness or loudness per time frame or level.

19. The system of claim 17 wherein the previously determined metadata for the reference audio content signal includes reference measures of crest factor and scaling factor for the reference audio content signal, and wherein the memory has stored therein further instructions that when executed by the processor

compute input measures of crest factor and scaling factor for the user content audio signal,

calculate an input measure of perceptual loudness or level for the user content audio signal, using i) the input measures of crest factor and scaling factor, and ii) the known gain and speaker sensitivity of the audio power amplifier and speaker,

obtain a reference measure of perceptual loudness or level, and

based on the input and reference measures of perceptual loudness or level, adjust at least one of the scalar gain, the spectral shaping filtering, and the dynamic range control setting.

20. The system of claim 19 wherein the memory has instructions that when executed by the processor calculate the reference measure of perceptual loudness or level using i) the reference measures of crest factor and scaling factor, and ii) the known gain and speaker sensitivity of the audio power amplifier and speaker.

21. The system of claim 19 wherein the memory has instructions that when executed by the processor obtain the reference measure of perceptual loudness or level via lookup in the metadata.

22. The system of claim 17 wherein the memory has stored therein further instructions that when executed by the processor

access the reference audio content signal that is received through a communications transceiver from another remote node of the Internet and compute a reference measure of a spectral content in the reference audio content signal,

compute an input measure of the spectral content in the user content signal,

compare the reference measure of the spectral content with the input measure of the spectral content, and

adjust the spectral shaping filtering based on a) having compared the reference measure with the input measure of the spectral content, b) user volume setting for playback through the audio power amplifier and speaker, and c) gain and speaker sensitivity of the audio power amplifier and speaker.