Metadata driven dynamic range control

• US 9,607,624 B2
• Filed: 03/26/2014
• Issued: 03/28/2017
• Est. Priority Date: 03/29/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Baumgarte, Frank M.
• Primary Examiner(s): Santiago Cordero, Marivelisse
• Assistant Examiner(s): Ky, Kevin
• Application Number:
  US14/226,596
• Publication Number:
  US 20140297291A1
• Time in Patent Office: 1,098 Days
• Field of Search: 704/500
• US Class Current: 1/1
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• 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

Abstract

A system for encoding and applying Dynamic Range Control/Compression (DRC) gain values to a piece of sound program content is described. In particular, a set of DRC gain values representing a DRC gain curve for the piece of content may be divided into frames corresponding to frames of the piece of content. A set of fields may be included with an audio signal representing the piece of content. The additional fields may represent the DRC gain values using linear or spline interpolation. The additional fields may include 1) an initial gain value for each DRC frame, 2) a set of slope values at particular points in the DRC curve, 3) a set of time delta values for each consecutive pair of slope values, and/or 4) one or more gain delta values representing changes of DRC gain values in the DRC gain curve between points of the slope values.

Claims

1. A method for applying Dynamic Range Control (DRC) gain values to a piece of sound program content, comprising:

gathering, by an electronic audio playback device, multi-band DRC configuration information, wherein the multi-band DRC configuration information indicates the number of independent DRC gain sequences in a bitstream and the number of DRC channel groups in the bitstream for an entire audio band or for multiple sub-bands;

parsing the bitstream to retrieve quantized data values representing DRC gain values for each DRC gain frame;

decoding the quantized data values using code tables to generate DRC gain data that has undergone encoding to reduce bit rate of the bitstream;

decoding the DRC gain data to undo said encoding, so as to generate DRC gain values to be applied to corresponding audio frames of the piece of sound program content, wherein decoding the DRC gain data comprises

extracting one or more time delta values from the bitstream, wherein the time delta values indicate time separation between pairs of DRC gain values, and

extracting one or more gain delta values from the bitstream, wherein the gain delta values indicate DRC gain value differences between pairs of DRC gain values; and

applying the DRC gain values to the entire audio band or multiple sub-bands of each audio frame.

2. The method of claim 1, wherein the DRC configuration information is gathered from a header of the bitstream.

3. The method of claim 1, further comprising:

extracting a coding mode data value from the bitstream for each DRC gain frame in each DRC channel group, wherein the coding mode data value represents an encoding mode of the DRC gain values in each corresponding DRC gain frame.

4. The method of claim 3, further comprising:

extracting an initial gain value from the bitstream for each DRC gain frame, wherein the initial gain value is used to apply gain to a first segment of a corresponding audio frame.

5. The method of claim 1, further comprising:

extracting an initial gain value from the bitstream for each DRC gain frame, wherein the initial gain value is used to apply gain to a first segment of a corresponding audio frame, and wherein decoding the DRC gain data comprises

generating a DRC gain value for the first segment of an audio frame based on the initial gain value for a corresponding DRC gain frame; and

generating DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, time delta values, and gain delta values associated with the first and second segments.

6. The method of claim 5, wherein the interpolation is a linear interpolation or a window-based overlap-add interpolation.

7. The method of claim 1 wherein decoding the DRC gain data comprises:

extracting slope values from the bitstream for each DRC gain frame, wherein the slope values correspond to sampled points of a DRC gain curve representing the DRC gain values.

8. The method of claim 7 wherein decoding the DRC gain data comprises:

generating a DRC gain value for the first segment of an audio frame based on the initial gain value for a corresponding DRC gain frame; and

generating DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, a slope value, time delta values, and gain delta values associated with the first and second segments.

9. The method of claim 8, wherein the interpolation is a spline interpolation.

10. The method of claim 1, further comprising:

filtering the audio signal to split each audio frame into multiple sub-bands.

11. An article of manufacture comprising:

a non-transitory machine-readable medium having stored therein instructions which program a processor to gather multi-band dynamic range control (DRC) configuration information that indicates the number of independent DRC gain sequences in a bitstream and the number of DRC channel groups in the bitstream, wherein the bitstream contains a piece of sound program content, wherein the multi-band DRC configuration information refers to either an entire audio band or to multiple sub-bands,

the programmed processor to parse the bitstream to retrieve quantized data values that represent DRC gain values for each DRC gain frame, decode the quantized data values using code tables to generate DRC gain data that has undergone encoding to reduce bit rate of the bitstream, decode the DRC gain data to undo said encoding, so as to generate DRC gain values by extracting one or more time delta values from the bitstream, wherein each of the time delta values indicates a time separation between a pair of DRC gain values, and by extracting one or more gain delta values from the bitstream, wherein each of the gain delta values indicates a gain value difference between a pair of DRC gain values, and apply the DRC gain values to corresponding audio frames of the piece of sound program content, wherein the DRC gain values are applied to the entire audio band or to multiple sub-bands of each audio frame.

12. The article of manufacture of claim 11, wherein the machine-readable medium has instructions that program the processor to gather the DRC configuration information from a header of the bitstream.

13. The article of manufacture of claim 11 wherein the machine-readable medium contains further stored instructions that program the processor to extract a coding mode data value from the bitstream, for each DRC gain frame in each DRC channel group, wherein the coding mode data value represents an encoding mode of the DRC gain values in each corresponding DRC gain frame.

14. The article of manufacture of claim 13 wherein the machine-readable medium contains further instructions stored therein that program the processor to extract an initial gain value from the bitstream for each DRC gain frame, and apply gain to a first segment of a corresponding audio frame using the extracted initial gain value.

15. The article of manufacture of claim 14 wherein the machine-readable medium contains further instructions that program the processor to generate a DRC gain value for the first segment of an audio frame, based on the initial gain value for a corresponding DRC gain frame, and

generate DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, time delta values, and gain delta values associated with the first and second segments.

16. The article of manufacture of claim 14 wherein the machine-readable medium has stored therein further instructions that program the processor to extract slope values from the bitstream, for each DRC gain frame, wherein the slope values correspond to sampled points of a DRC gain curve representing the DRC gain values.

17. The article of manufacture of claim 16 wherein the machine-readable medium has stored therein further instructions that program the processor to generate a DRC gain value for the first segment of an audio frame based on the initial gain value for a corresponding DRC gain frame, and generate DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, a slope value, time delta values, and gain delta values associated with the first and second segments.

18. The article of manufacture of claim 17 wherein the instructions stored in the machine-readable medium program the processor to perform a linear interpolation when generating the DRC gain values for the second segment of the audio frame.

19. An article of manufacture comprising:

a non-transitory machine-readable medium having stored therein instructions which program a processor to gather multi-band dynamic range control (DRC) configuration information that indicates the number of independent DRC gain sequences in a bitstream and the number of DRC channel groups in the bitstream, wherein the bitstream contains a piece of sound program content, wherein the multi-band DRC configuration information refers to either an entire audio band or to multiple sub-bands,

the programmed processor to parse the bitstream to retrieve quantized data values that represent DRC gain values for each DRC gain frame, decode the quantized data values using code tables to generate DRC gain data,

decode the DRC gain data by i) extracting one or more time delta values from the bitstream, wherein each of the time delta values indicates a time separation between pairs of DRC gain values, and ii) extracting one or more gain delta values from the bitstream, wherein the gain delta values indicate DRC gain value differences between pairs of DRC gain values, to generate DRC gain values, and

apply the DRC gain values to corresponding audio frames of the piece of sound program content, wherein the DRC gain values are applied to the entire audio band or to multiple sub-bands of each audio frame.

20. The article of manufacture of claim 19 wherein the machine-readable medium contains further stored instructions that program the processor to extract a coding mode data value from the bitstream, for each DRC gain frame in each DRC channel group, wherein the coding mode data value represents an encoding mode of the DRC gain values in each corresponding DRC gain frame.

21. The article of manufacture of claim 19 wherein the machine-readable medium contains further instructions stored therein that program the processor to extract an initial gain value from the bitstream for each DRC gain frame, and apply gain to a first segment of a corresponding audio frame using the extracted initial gain value.

22. The article of manufacture of claim 21 wherein the machine-readable medium has stored therein instructions that program the processor to extract one or more time delta values from the bitstream, wherein each of the time delta values indicates a time separation between pairs of DRC gain values, and extract one or more gain delta values from the bitstream, wherein the gain delta values indicate DRC gain value differences between pairs of DRC gain values.

23. The article of manufacture of claim 22 wherein the machine-readable medium contains further instructions that program the processor to generate a DRC gain value for the first segment of an audio frame, based on the initial gain value for a corresponding DRC gain frame, and

generate DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, time delta values, and gain delta values associated with the first and second segments.

24. The article of manufacture of claim 19 wherein the machine-readable medium has stored therein further instructions that program the processor to extract slope values from the bitstream, for each DRC gain frame, wherein the slope values correspond to sampled points of a DRC gain curve representing the DRC gain values.

25. The article of manufacture of claim 24 wherein the machine-readable medium has stored therein further instructions that program the processor to generate a DRC gain value for the first segment of an audio frame based on the initial gain value for a corresponding DRC gain frame, and generate DRC gain values for a second segment of the audio frame using interpolation based on the DRC gain value generated for the first segment, a slope value, time delta values, and gain delta values associated with the first and second segments.

26. The article of manufacture of claim 25 wherein the instructions stored in the machine-readable medium program the processor to perform a linear interpolation when generating the DRC gain values for the second segment of the audio frame.