Audio gain control using specific-loudness-based auditory event detection

• US 8,144,881 B2
• Filed: 03/30/2007
• Issued: 03/27/2012
• Est. Priority Date: 04/27/2006
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Crockett, Brett Graham, Seefeldt, Alan Jeffrey
• Primary Examiner(s): Mei, Xu
• Application Number:
  US12/226,698
• Publication Number:
  US 20090220109A1
• Time in Patent Office: 1,824 Days
• Field of Search: 381/98, 381101-107, 381/56, 381/80, 381/81, 381 941- 943
• US Class Current: 381/56
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 25/21 the extracted parameters being power information
• CPC Class Codes: G10L 25/51 for comparison or discrimination
• CPC Class Codes: H03G 1/00 Details of arrangements for controlling amplification
• 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 7/007 of digital or coded signals
• CPC Class Codes: H03G 9/005 of digital or coded signals
• CPC Class Codes: H04R 2430/03 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

In one disclosed aspect, dynamic gain modifications are applied to an audio signal at least partly in response to auditory events and/or the degree of change in signal characteristics associated with said auditory event boundaries. In another aspect, an audio signal is divided into auditory events by comparing the difference in specific loudness between successive time blocks of the audio signal.

Claims

1. A method for modifying a parameter of an audio dynamics processor, comprising

detecting changes in spectral characteristics with respect to time in an audio signal,

identifying as auditory event boundaries changes greater than a threshold in spectral characteristics with respect to time in said audio signal, wherein an audio segment between consecutive boundaries constitutes an auditory event,

generating a parameter-modifying dynamically-varying control signal based on said identified event boundaries, and

modifying the parameter of the audio dynamics processor as a function of the control signal.

2. A method according to claim 1 wherein the parameter is one of attack time, release time, and ratio.

3. A method according to claim 1 wherein the parameter modified is a gain-smoothing time constant.

4. A method according to claim 3 wherein the gain-smoothing time constant is a gain-smoothing attack time constant.

5. A method according to claim 3 wherein the gain-smoothing time constant is a gain-smoothing release time constant.

6. A method according to claim 1 wherein said parameter-modifying control signal is based on the location of said identified auditory event boundaries and the degree of change in spectral characteristics associated with each of said auditory event boundaries.

7. A method according to claim 6 wherein generating a parameter modifying control signal comprises

providing an impulse at each of auditory event boundaries, each such impulse having an amplitude proportional to the degree of said changes in spectral characteristics, and

time smoothing each such impulse so that its amplitude decays smoothly toward zero.

8. A method according to claim 1 wherein changes in spectral characteristics with respect to time are detected by comparing differences in specific loudness.

9. A method according to claim 8 wherein said audio signal is represented by a discrete time sequence x[n] that has been sampled from an audio source at a sampling frequency f_s and the changes in spectral characteristics with respect to time are calculated by comparing the difference in specific loudness N[b,t] across frequency bands b between successive time blocks t.

10. A method according to claim 9 wherein the difference in spectral content between successive time blocks of the audio signal is calculated according to

11. A method according to claim 9 wherein the difference in spectral content between successive time blocks of the audio signal is calculated according to

12. A non-transitory computer-readable storage medium encoded with a computer program for causing a computer to perform the method of claim 1.

13. A method for modifying a parameter of an audio dynamics processor, comprising

detecting changes in a signal characteristic with respect to time in an audio signal,

identifying as auditory event boundaries changes greater than a threshold in said signal characteristic with respect to time in said audio signal, wherein an audio segment between consecutive boundaries constitutes an auditory event,

generating a parameter-modifying dynamically-varying control signal based on said auditory event, and

modifying the parameter of the audio dynamics processor as a function of the control signal.

14. An audio processing method in which a processor receives an input channel and generates an output channel that is generated by applying dynamic gain modifications to the input channel, comprising

detecting changes in signal characteristics with respect to time in the audio input channel,

identifying as auditory event boundaries changes in signal characteristics with respect to time in said input channel, wherein an audio segment between consecutive boundaries constitutes an auditory event in the channel, and

generating all or some of one or more dynamically-varying parameters of the audio dynamic gain modification method in response to auditory events and/or the degree of change in signal characteristics associated with said auditory event boundaries.

15. Apparatus for modifying a parameter of an audio dynamics processor, comprising

means for detecting changes in spectral characteristics with respect to time in an audio signal,

means for identifying as auditory event boundaries changes greater than a threshold in spectral characteristics with respect to time in said audio signal, wherein an audio segment between consecutive boundaries constitutes an auditory event,

means for generating a parameter-modifying dynamically-varying control signal based on said identified event boundaries, and

means for modifying the parameter of the audio dynamics processor as a function of the control signal.