AUDIO ENCODER OPERABLE IN PREDICTION OR NON-PREDICTION MODE

• US 20190311725A1
• Filed: 06/24/2019
• Published: 10/10/2019
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: Purnhagen, Heiko, Carlsson, Pontus, Villemoes, Lars
• Granted Patent: US 10,553,226 B2
• Time in Patent Office: Days
• 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 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• 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: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: G10L 25/12 the extracted parameters being prediction coefficients
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

The invention provides methods and apparatuses for encoding a stereo audio signal having a left channel and a right channel. The apparatus includes a prediction coefficient estimator, downmixer, and multiplexer. The encoder is configured operate either in a prediction mode or a non-prediction mode.

Claims

1. A method for encoding a stereo audio signal having a left channel and a right channel, the method comprising:

estimating a prediction coefficient using the left channel and the right channel;

downmixing the left channel and the right channel to produce a mid signal and a residual signal using the prediction coefficient; and

multiplexing the mid signal, the residual signal, and the prediction coefficient to generate an audio bitstream,

wherein the prediction coefficient minimizes an energy of the residual signal, and the encoding operates in either a prediction mode or a non-prediction mode for a time frame based on a value of the prediction coefficient,

wherein the encoding operates in the non-prediction mode when the value of the prediction coefficient is zero.

2. The method of claim 1 wherein the prediction coefficient comprises a prediction coefficient for each of a plurality of frequency bands.

3. The method of claim 1 wherein, when the encoding operates in the prediction mode, the residual signal represents a difference between a side signal and a predicted version of the side signal, and the downmixing produces the predicted version of the side signal based on the mid signal and the prediction coefficient.

4. The method of claim 3 wherein, when the encoding operates in the non-prediction mode, the residual signal represents the side signal, and the downmixing produces the mid signal based on a sum of the left channel and the right channel and produces the residual signal based on a difference between the left channel and the right channel.

5. The method of claim 1 wherein the prediction coefficient is determined based on an optimization using a mean squared error criterion.

6. The method of claim 1 wherein, when the downmixer operates in the prediction mode, the downmixer produces the residual signal using a filter having three taps.

7. The method of claim 1 wherein the prediction coefficient is a real valued coefficient.

8. The method of claim 1 wherein the prediction coefficient is a complex valued coefficient.

9. The method of claim 1 wherein the prediction coefficient is quantized and coded in the audio bitstream.

10. The method of claim 1 wherein the prediction coefficient is coded in the audio bitstream using a plurality of parts.

21. A non-transitory computer-readable medium containing instructions that when executed by a processor perform the method of claim 1.

11. An apparatus for encoding a stereo audio signal having a left channel and a right channel, the apparatus comprising:

an estimator for generating a prediction coefficient using the left channel and the right channel;

a downmixer for mixing the left channel and the right channel to produce a mid signal and a residual signal using the prediction coefficient; and

a multiplexer for combining the mid signal, the residual signal, and the prediction coefficient to generate an audio bitstream,

wherein the prediction coefficient minimizes an energy of the residual signal, and the encoding operates in either a prediction mode or a non-prediction mode for a time frame based on a value of the prediction coefficient,

wherein the encoding operates in the non-prediction mode when the value of the prediction coefficient is zero.

12. The apparatus of claim 11 wherein the prediction coefficient comprises a prediction coefficient for each of a plurality of frequency bands.

13. The apparatus of claim 11 wherein, when the encoding operates in the prediction mode, the residual signal represents a difference between a side signal and a predicted version of the side signal, and the mixing produces the predicted version of the side signal based on the mid signal and the prediction coefficient.

14. The apparatus of claim 13 wherein, when the encoding operates in the non-prediction mode, the residual signal represents the side signal, and the downmixing produces the mid signal based on a sum of the left channel and the right channel and produces the residual signal based on a difference between the left channel and the right channel.

15. The apparatus of claim 11 wherein the prediction coefficient is determined based on an optimization using a mean squared error criterion.

16. The apparatus of claim 11 wherein, when the downmixer operates in the prediction mode, the downmixer produces the residual signal using a filter having three taps.

17. The apparatus of claim 11 wherein the prediction coefficient is a real valued coefficient.

18. The apparatus of claim 11 wherein the prediction coefficient is a complex valued coefficient.

19. The apparatus of claim 11 wherein the prediction coefficient is quantized and coded in the audio bitstream.

20. The apparatus of claim 11 wherein the prediction coefficient is coded in the audio bitstream using a plurality of parts.