Advanced stereo coding based on a combination of adaptively selectable left/right or mid/side stereo coding and of parametric stereo coding

• US 9,905,230 B2
• Filed: 06/09/2015
• Issued: 02/27/2018
• Est. Priority Date: 03/17/2009
• Status: Active Grant

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: Purnhagen, Heiko, Carlsson, Pontus, Kjoerling, Kristofer
• Primary Examiner(s): Goins, Davetta W
• Assistant Examiner(s): SELLERS, DANIEL R
• Application Number:
  US14/734,088
• Publication Number:
  US 20150269948A1
• Time in Patent Office: 994 Days
• Field of Search: 381 22
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• 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 19/18 Vocoders using multiple modes
• 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 2400/03 Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 H04S2400/01 takes precedence
• CPC Class Codes: H04S 2420/03 Application of parametric coding in stereophonic audio systems
• CPC Class Codes: H04S 3/02 of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other
• CPC Class Codes: H04S 5/00 Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation
• CPC Class Codes: H04S 5/005 of the pseudo five- or more-channel type, e.g. virtual surround
• CPC Class Codes: H04S 5/02 of the pseudo four-channel type, e.g. in which rear channel signals are derived from two-channel stereo signals

Abstract

The application relates to audio encoder and decoder systems. An embodiment of the encoder system comprises a downmix stage for generating a downmix signal and a residual signal based on a stereo signal. In addition, the encoder system comprises a parameter determining stage for determining parametric stereo parameters such as an inter-channel intensity difference and an inter-channel cross-correlation. Preferably, the parametric stereo parameters are time- and frequency-variant. Moreover, the encoder system comprises a transform stage. The transform stage generates a pseudo left/right stereo signal by performing a transform based on the downmix signal and the residual signal. The pseudo stereo signal is processed by a perceptual stereo encoder. For stereo encoding, left/right encoding or mid/side encoding is selectable. Preferably, the selection between left/right stereo encoding and mid/side stereo encoding is time- and frequency-variant.

Claims

1. An encoder system encoding a stereo signal to a bitstream signal, the encoder system comprising:

a downmix stage generating a downmix signal and a residual signal from the stereo signal;

a perceptual encoder stage selecting

encoding based on a sum of the downmix signal and the residual signal and based on a difference of the downmix signal and the residual signal, or

encoding based on the downmix signal and based on the residual signal.

2. The encoder system of claim 1, wherein the perceptual encoding stage comprises:

a transformation stage performing a transform of the downmix signal and the residual signal to generate a pseudo left/right stereo signal; and

a perceptual encoder encoding the pseudo left/right stereo signal by selecting

left/right perceptual encoding or

mid/side perceptual encoding.

3. The encoder system of claim 1, wherein the perceptual encoding stage comprises

a transformation stage performing a sum and difference transform of the downmix signal and the residual signal to generate a pseudo left/right stereo signal for one or more or all used frequency bands.

4. The encoder system of claim 3, wherein

the perceptual encoding stage comprises a decision stage deciding between L/R perceptual encoding and M/S perceptual encoding;

encoding based on the downmix signal and residual signal is selected when the decision stage decides M/S perceptual decoding, and

encoding based on the sum and difference is selected when the decision stage decides L/R perceptual decoding.

5. The encoder system of claim 2, wherein the perceptual encoder decides between

left/right encoding or

mid/side encoding

based on the pseudo stereo signal.

6. The encoder system of claim 1, wherein the encoder system selects between

parametric stereo encoding the stereo signal to the bitstream signal or

left/right encoding the stereo signal to the bitstream signal.

7. The encoder system of claim 2, wherein the perceptual encoder performs a left/right to mid/side transform using the pseudo stereo signal.

8. The encoder system of claim 1, wherein the encoder system comprises a parameter determining stage determining a parametric stereo parameter.

9. The encoder system of claim 8, wherein the parametric stereo parameter comprises

a parameter indicating a inter-channel intensity difference;

and/or

a parameter indicating a inter-channel cross-correlation.

10. An encoder system encoding a stereo signal to a bitstream signal, the encoder system comprising:

a downmix stage generating a downmix signal and a residual signal from the stereo signal;

a transform stage performing a transform based on the downmix signal and the residual signal to generate a pseudo left/right stereo signal; and

a perceptual encoder stage encoding the pseudo left/right stereo signal, wherein the perceptual encoder stage selects

left/right perceptual encoding or

mid/side perceptual encoding.

11. A decoder system decoding a bitstream signal including a parametric stereo parameter to a stereo signal, the decoder system comprising:

a perceptual decoding stage generating a first signal and a second signal by decoding the bitstream signal, and outputting a downmix signal and a residual signal by selecting the downmix signal and the residual signal

based on a sum of the first signal and of the second signal and based on a difference of the first signal and of the second signal, or

based on the first signal and based on the second signal; and

an upmixing stage generating the stereo signal based on the downmix signal, the residual signal and the parametric stereo parameter.

12. The decoder system of claim 11, wherein the perceptual decoding stage comprises:

a perceptual stereo decoder generating a pseudo stereo signal based on the bitstream signal, by selectively performing

left/right perceptual decoding, or

mid/side perceptual decoding; and

a transform stage performing a transform on the pseudo stereo signal for generating the downmix signal and the residual signal.

13. The decoder system of claim 11, wherein the perceptual decoding stage comprises:

a transform stage performing a sum and difference transform based on the first signal and the second signal for one or more or all used frequency bands.

14. The decoder system of claim 13, wherein

the perceptual decoding stage comprises a selector selecting between L/R perceptual decoding and M/S perceptual decoding;

the downmix signal and the residual signal is selected to be based on the sum of the first signal and of the second signal and based on the difference of the first signal and of the second signal when the selector selects L/R perceptual decoding, and

the downmix signal and the residual signal is selected to be based on the first signal and based on the second signal when the selector selects M/S perceptual decoding.

15. The decoder system of claim 11, wherein the decoder system switches between

parametric stereo decoding the bitstream signal to the stereo signal or

left/right decoding the bitstream signal to the stereo signal.