Bitstream Syntax for Spatial Voice Coding

Patent metadata

Field	Value
Publication number	US-2016155447-A1
Application number	US-201414392287-A
Country	US
Kind code	A1
Filing date	Jun 26, 2014
Priority date	Jun 27, 2013
Publication date	Jun 2, 2016
Grant date	—

Abstract

An encoding system ( 100 ) encodes a first (E 1 ) and further (E 2 , E 3 ) audio signals as a layered bitstream (B), wherein a quantizer for each frequency band of each signal is selected using a rate allocation rule based on signal-specific rate allocation data, a spectral envelope of the signal and a reference level (EnvE 1 Max), which is determined based on the spectral envelope of the first signal and is not necessarily included in the bitstream. Further disclosed is a decoding system for reconstructing the audio signals based on the bitstream. In embodiments, the bitstream has a basic layer (B E1 ), which contains data that enable decoding of the first audio signal, and a spatial layer (B spatial ) facilitating decoding of the further audio signal(s). In embodiments, the encoding system prepares the bitstream subject to a basic-layer bitrate constraint and a total bitrate constraint.

First claim

1 . A scalable adaptive audio encoding system, comprising:
an envelope analyzer for outputting spectral envelopes on the basis of a time frame of a frequency-domain representation of a first audio signal (E 1 ) and at least one further audio signal (E 2 , E 3 ); a multichannel encoder including: a rate allocation component (for determining: first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; and second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; and a quantization component configured to retrieve the quantizers indicated by the rate allocation component and to quantize the first audio signal and the at least one further audio signal using the quantizers thus retrieved, and to output signal data; and a multiplexer for outputting a bitstream (B) comprising the spectral envelopes, the signal data and the rate allocation data, wherein the rate allocation component is configured with a first rate allocation rule (R 1 ), by which the first rate allocation data, the spectral envelope of the first audio signal (EnvE 1 ) and a reference level (EnvE 1 Max) derived from the spectral envelope of the first audio signal using a predefined non-zero functional determine the quantizers for the first audio signal, and with a second rate allocation rule (R 2 ), by which the second rate allocation data, the spectral envelope of the at least one further audio signal (EnvE 2 , EnvE 3 ) and said reference level (EnvE 1 Max) derived from the first audio signal determine the quantizers for the at least one further audio signal.

2 . The audio encoding system of claim 1 , wherein the multiplexer is configured to form a bitstream with a basic layer (B E1 ) and a spatial layer (B spatial ), wherein the basic layer comprises the spectral envelope and the signal data of the first audio signal and the first rate allocation data, and allows independent reconstruction of the first audio signal.

3 . The audio encoding system of claim 2 , wherein the rate allocation component is configured to determine a first coding bitrate (bE 1 ) occupied by the basic layer of the bitstream and to determine the first rate allocation data subject to a basic-layer bitrate constraint (bE 1 max).

4 . The audio encoding system of claim 2 , wherein the rate allocation component is configured to determine a total coding bitrate (bTot) occupied by the bitstream and to determine the first and second rate allocation data subject to a total bitrate constraint (bTotMax).

5 . The audio encoding system of claim 1 , wherein:
the collection of predefined quantizers is ordered with respect to fineness; and the first and/or second rate allocation rule is/are designed to indicate a finer quantizer for a frequency band with higher energy content than a frequency band of the same signal with lower energy content, as indicated by the respective spectral envelope.

6 . The audio encoding system of claim 5 , wherein the first and/or second rate allocation rule is/are designed to refer to the energy content normalized by the reference level (EnvE 1 Max) derived from the first audio signal.

7 . The audio encoding system of claim 5 , wherein:
the rate allocation data include an offset parameter (AllocOffsetE 1 , AllocOffsetE 2 E 3 ); and the first and/or second rate allocation rule is designed to refer to the energy content normalized by the offset parameter.

8 . (canceled)

9 . (canceled)

10 . (canceled)

11 . The audio encoding system of claim 5 , wherein the rate allocation data further includes an augmentation parameter (AllocOverE 1 , AllocOverE 2 E 3 ) indicating a subset of the frequency bands for which the first/and or second rate allocation rule is overridden.

12 . (canceled)

13 . The audio encoding system of claim 1 , wherein the multiplexer is configured to output a bitstream comprising bitstream units corresponding to one or more time frames of the audio signals, in which the spectral envelope and signal data of the first audio signal and the first rate allocation data are non-interlaced with the spectral envelopes and signal data of the at least one further audio signal and the second rate allocation data in each bitstream unit.

14 . The audio encoding system of claim 13 , wherein the multiplexer is configured to output a bitstream comprising bitstream units in which the spectral envelope and signal data of the first audio signal and the first rate allocation data precede the spectral envelopes and signal data of the at least one further audio signal and the second rate allocation data in each bitstream unit.

15 . The audio encoding system of claim 13 , wherein the multiplexer is configured to output a bitstream of bitstream units which further comprise a gain profile (g) for noise suppression in connection with mono decoding, wherein the gain profile precedes the spectral envelopes and signal data of the at least one further audio signal and the second rate allocation data in each bitstream unit.

16 . (canceled)

17 . The audio encoding system of claim 1 , further comprising:
a spatial analyzer configured to receive a plurality of input audio signals (W, X, Y) and to determine, based on these, frame-wise decomposition parameters (K=(d, φ, θ)); and an adaptive rotation stage configured to receive said plurality of input audio signals and to output said plurality of audio signal (E 1 , E 2 , E 3 ) by applying an energy-compacting orthogonal transformation, wherein quantitative properties of the transformation are determined by the decomposition parameters.

18 . (canceled)

19 . The audio encoding system of claim 3 , wherein the rate allocation component is configured to:
determine the first rate allocation data based on a joint comparison of frequency bands of all spectral envelopes while repeatedly estimating a first coding bitrate (bE 1 ) occupied by the basic layer of the bitstream, wherein the first rate allocation data are determined subject to a basic-layer bitrate constraint (bE 1 Max) or, if the basic-layer bitrate constraint is not saturated, subject to a total bitrate constraint (bTot); and determine the second rate allocation data subject to the total bitrate constraint (bTot) and in dependence of whether the basic-layer bitrate constraint was saturated, wherein,
if the basic-layer bitrate constraint was not saturated, the second rate allocation data are determined by the joint comparison of frequency bands of all spectral envelopes; and
if the basic-layer bitrate constraint was saturated, the second rate allocation data are determined based on a joint comparison of frequency bands of the spectral envelope(s) of the at least one further audio signal.

20 . (canceled)

21 . An audio encoding method comprising:
generating spectral envelopes (EnvE 1 , EnvE 2 , EnvE 3 ) on the basis of a time frame of a frequency-domain representation of a first audio signal (E 1 ) and at least one further audio signal (E 2 , E 3 ); determining first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; determining second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; quantizing the first audio signal and the at least one further

Assignees

• Dolby Lab Licensing Corp
• Dolby Int Ab

Inventors

• Klejsa Janusz
• Samuelsson Leif Jonas
• Purnhagen Heiko
• Dickins Glenn N

Classifications

• G10L19/032

  Quantisation or dequantisation of spectral components · CPC title

• G10L19/0204

  using subband decomposition · CPC title

• G10L19/0212

  using orthogonal transformation · CPC title

• G10L19/002

  Dynamic bit allocation (for perceptual audio coders G10L19/032) · CPC title

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · CPC title