Back to results
US 12,223,966 B2Granted
Selectable linear predictive or transform coding modes with advanced stereo coding
AssigneeDolby International AB
InventorsHeiko Purnhagen, Pontus Carlsson, Kristofer Kjoerling
Life of this patent
Estimating the term…
Abstract
Methods and systems for advanced stereo processing of an audio signal are disclosed. The methods and systems include selecting a coding mode of either transform coding or linear predictive coding and performing advanced stereo processing when in the selected coding mode. Both encoding and decoding operations are provided.
Claims20
A method for encoding a stereo input signal comprising a left channel and a right channel, and having a perceptual stereo image, the method comprising:
- selecting either a modified discrete cosine transform (MDCT) based transform coding mode or a linear predictive coding mode as a selected coding mode;
- encoding the stereo input signal using only the selected coding mode to produce an encoded output signal;
- and
- generating a bitstream signal including the encoded output signal,
- wherein, if the linear predictive coding mode is selected, the encoding comprises:
- downmixing the stereo input signal to a mono signal, the mono signal being a sum of the left channel and the right channel,
- estimating stereo image parameters, for reconstructing a stereo signal that approximates the perceptual stereo image of the stereo input signal from the mono signal,
- generating a residual signal that indicates an error associated with representing the stereo signal by the mono signal and the estimated stereo image parameters,
- encoding the mono signal using linear predictive coding to produce an encoded mono signal, and
- outputting the encoded mono signal, the residual signal and the stereo image parameters as the encoded output signal,
- wherein, if the MDCT based transform coding mode is selected, the encoding comprises:
- analyzing the stereo input signal by applying both mid/side stereo coding and left/right stereo coding and selecting either a mid/side stereo coding mode or a left/right stereo coding mode based on an estimated entropy for each stereo coding mode,
- encoding the stereo input signal using the selected stereo coding mode in a first frequency band to produce an encoded stereo signal in a first frequency band,
- downmixing the stereo input signal to a mono signal in a second frequency band,
- encoding the mono signal in the second frequency band using MDCT based transform coding to produce an encoded mono signal in the second frequency band, and
- outputting the encoded stereo signal in the first frequency band and the encoded mono signal in the second frequency band as the encoded output signal.
13 more elements
A device for encoding a stereo input signal comprising a left channel and a right channel, and having a perceptual stereo image, to produce an encoded output signal, the device comprising:
- a mode selector for selecting either a modified discrete cosine transform (MDCT) based transform coding mode or a linear predictive coding mode;
- a MDCT based transform encoder for encoding the stereo input signal if the selected coding mode is the MDCT based transform coding mode but not if the selected coding mode is the linear predictive coding mode;
- a linear predictive encoder for encoding the stereo input signal if the selected coding mode is the linear predictive coding mode but not if the selected coding mode is the MDCT based transform coding mode;
- and
- a bitstream generator for generating a bitstream signal including the encoded output signal, wherein the linear predictive encoder is configured to:
- downmix the stereo input signal to a mono signal, the mono signal being a sum of the left channel and the right channel,
- estimate stereo image parameters, for reconstructing a stereo signal that approximates the perceptual stereo image of the stereo input signal, from the mono signal,
- generate a residual signal that indicates an error associated with representing the stereo signal by the mono signal and the estimated stereo image parameters,
- encode the mono signal using linear predictive coding to produce an encoded first mono signal, and
- output the encoded mono signal, the residual signal and the estimated stereo image parameters as the encoded output signal,
- wherein the MDCT based transform encoder is configured to:
- analyze the stereo input signal by applying both mid/side stereo coding and left/right stereo coding and selecting either a mid/side stereo coding mode or a left/right stereo coding mode based on an estimated entropy for each stereo coding mode,
- encode the stereo input signal using the selected stereo coding mode in a first frequency band to produce an encoded stereo signal in the first frequency band,
- downmix the stereo input signal to a mono signal in a second frequency band,
- encode the mono signal in the second frequency band using MDCT based transform coding to produce an encoded mono signal in the second frequency band, and
- output the encoded stereo signal in the first frequency band and the encoded mono signal in the second frequency band as the encoded output signal.
13 more elements
A method for decoding a bitstream signal to produce a decoded output signal having a left channel and a right channel, the method comprising:
- extracting an encoded audio signal from the bitstream signal, the encoded audio signal generated by encoding an input stereo audio signal having a left input channel and a right input channel using a selected coding mode, wherein the selected coding mode is one of a modified discrete cosine transform (MDCT) based transform coding mode or a linear predictive coding mode;
- decoding the encoded audio signal using only the selected coding mode to produce a decoded signal;
- and
- outputting the decoded signal as the decoded output signal,
- wherein, if the selected coding mode is the linear predictive coding mode, the decoding comprises:
- receiving an encoded mono signal, the encoded mono signal being a sum of the left input channel and the right input channel of the input stereo audio signal,
- decoding the encoded mono signal using linear predictive decoding to produce a decoded mono signal,
- extracting stereo image parameters and a residual signal from the bitstream signal for reconstructing a stereo audio signal that approximates a perceptual stereo image of the input stereo audio signal, wherein the residual signal indicates an error associated with representing the stereo audio signal by the mono signal and the stereo image parameters,
- reconstructing the stereo audio signal using the decoded mono signal, the residual signal and the stereo image parameters to produce a reconstructed stereo audio signal that approximates the perceptual stereo image of the input stereo audio signal, and
- outputting the reconstructed stereo audio signal as the decoded signal,
- wherein, if the selected coding mode is the MDCT based transform coding mode, the decoding comprises:
- receiving a stereo signal in a first frequency band, the stereo signal generated using a selected stereo coding mode, the selected stereo coding mode including either mid/side stereo coding or left/right stereo coding,
- receiving an encoded mono signal in a second frequency band,
- decoding the stereo signal in the first frequency band using the selected stereo coding mode to produce a decoded stereo signal in the first frequency band,
- decoding the encoded mono signal in the second frequency band using MDCT based transform decoding to produce a decoded mono signal in the second frequency band, and
- generating the decoded signal from the decoded stereo signal in the first frequency band and the decoded mono signal in the second frequency band.
13 more elements
A device for decoding a bitstream signal to produce a decoded output signal having a left channel and a right channel, the device comprising:
- a demultiplexer for extracting an encoded audio signal from the bitstream signal, the encoded audio signal generated by encoding an input stereo audio signal having a left input channel and a right input channel using a selected coding mode, wherein the selected coding mode is one of a modified discrete cosine transform (MDCT) based transform coding mode or a linear predictive coding mode;
- a MDCT based transform decoder for decoding the encoded audio signal if the selected coding mode is the MDCT based transform coding mode but not if the selected coding mode is the linear predictive coding mode;
- and
- a linear predictive decoder for decoding the encoded audio signal if the selected coding mode is the linear predictive coding mode but not if the selected coding mode is the MDCT based transform coding mode,
- wherein the linear predictive decoder is configured to:
- receive an encoded mono signal, the encoded mono signal being a sum of the left input channel and the right input channel of the input stereo audio signal,
- decode the encoded mono signal using linear predictive decoding to produce a decoded mono signal,
- extract stereo image parameters and a residual signal from the bitstream signal for reconstructing a stereo audio signal that approximates a perceptual stereo image of the input stereo audio signal, wherein the residual signal indicates an error associated with representing the stereo signal by the mono signal and the stereo image parameters,
- reconstruct the stereo audio signal using the decoded mono signal, the residual signal and the stereo image parameters to produce a reconstructed stereo audio signal that approximates the perceptual stereo image of the input stereo audio signal, and
- output the reconstructed stereo audio signal as the decoded output signal,
- wherein MDCT based transform decoder is configured to:
- receive a stereo signal in a first frequency band, the stereo signal generated using a selected stereo coding mode, the selected stereo coding mode including either a mid/side stereo coding mode or a left/right stereo coding mode,
- receive an encoded mono signal in a second frequency band,
- decode the stereo signal in the first frequency band using the selected stereo coding mode to produce a decoded stereo signal in the first frequency band,
- decode the encoded mono signal in the second frequency band using MDCT based transform decoding to produce a decoded mono signal in the second frequency band, and
- generate the decoded output signal from the decoded stereo signal in the first frequency band and the decoded mono signal in the second frequency band.
13 more elements
Dependencies are inferred from the claim text.