Audio encoding/decoding with syntax portions using forward aliasing cancellation

Patent metadata

Field	Value
Publication number	US-9257130-B2
Application number	US-201313736762-A
Country	US
Kind code	B2
Filing date	Jan 8, 2013
Priority date	Jul 8, 2010
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A codec supporting switching between time-domain aliasing cancellation transform coding mode and time-domain coding mode is made less liable to frame loss by adding a further syntax portion to the frames, depending on which the parser of the decoder may select between a first action of expecting the current frame to have, and thus reading forward aliasing cancellation data from the current frame and a second action of not-expecting the current frame to have, and thus not reading forward aliasing cancellation data from the current frame. In other words, while a bit of coding efficiency is lost due to the provision of the new syntax portion, it is merely the new syntax portion which provides for the ability to use the codec in case of a communication channel with frame loss. Without the new syntax portion, the decoder would not be capable of decoding any data stream portion after a loss and will crash in trying to resume parsing. Thus, in an error prone environment, the coding efficiency is prevented from vanishing by the introduction of the new syntax portion.

First claim

The invention claimed is:

1. Decoder apparatus for decoding a data stream comprising a sequence of frames comprising a plurality of respective frames into which time segments of an information signal are coded, respectively, comprising
a parser configured to parse the data stream, wherein the parser is configured to, in parsing the data stream, read a first syntax portion and a second syntax portion from a current frame; and
a reconstructor configured to reconstruct a current time segment of the information signal associated with the current frame based on information acquired from the current frame by the parsing, using, depending on a first selection, a Time-Domain Aliasing Cancellation transform decoding mode or a time-domain decoding mode, the first selection depending on the first syntax portion,
wherein the parser is configured to, in parsing the data stream, perform a first action of expecting the current frame to comprise, and thus reading forward aliasing cancellation data from the current frame or a second action of not-expecting the current frame to comprise, and thus not reading forward aliasing cancellation data from the current frame, wherein the parser is configured to perform a second selection selecting which of the first action and the second action is performed, depending on the second syntax portion,
wherein the reconstructor is configured to perform forward aliasing cancellation at a boundary between the current time segment and a previous time segment of a previous frame using the forward aliasing cancellation data,
wherein at least one of the parser and the reconstructor is implemented on a microprocessor, a programmable logic device or an electronic circuit.

2. Decoder apparatus according to claim 1 , wherein the first and second syntax portions are comprised by each frame, wherein the first syntax portion associates the respective frame from which the first syntax portion has been read, with a first frame type or a second frame type and, if the respective frame is of the second frame type, associates sub frames comprising a plurality of respective sub frames of a division of the respective frame, composed of a number of sub frames, with a respective one of a first sub frame type and a second sub frame type, wherein the reconstructor is configured to, if the first syntax portion associates the respective frame with the first frame type, use frequency domain decoding as a first version of the time-domain aliasing cancellation transform decoding mode to reconstruct the time segment associated with the respective frame, and, if the first syntax portion associates the respective frame with the second frame type, use, for each sub frame of the respective frame, transform coded excitation linear prediction decoding as a second version of the time-domain aliasing cancellation transform decoding mode to reconstruct a sub portion of the time segment of the respective frame, which is associated with the respective sub frame, if the first syntax portion associates the respective sub frame of the respective frame with the first sub frame type, and codebook excitation linear prediction decoding as the time-domain decoding mode to reconstruct a sub portion of the time segment of the respective frame, which is associated with the respective sub frame, if the first syntax portion associates the respective sub frame with the second sub frame type.

3. Decoder apparatus according to claim 2 , wherein the reconstructor is configured to
per frame of the first frame type, perform a spectral varying de-quantization of transform coefficient information within the respective frame of the first frame type based on scale factor information within the respective frame of the first frame type, and a re-transform on the de-quantized transform coefficient information to acquire a re-transformed signal segment extending, in time, over and beyond the time segment associated with the respective frame of the first frame type, and
per frame of the second frame type,
per sub frame of the first sub frame type of the respective frame of the second frame type,
derive a spectral weighting filter from LPC information within the respective frame of the second frame type,
spectrally weighting transform coefficient information within the respective sub frame of the first sub frame type using the spectral weighting filter, and
re-transform the spectrally weighted transform coefficient information to acquire a re-transformed signal segment extending, in time, over and beyond the sub portion of the time segment associated with the respective sub frame of the first sub frame type, and,

per sub frame of the second sub frame type of the respective frame of the second frame type,
derive an excitation signal from excitation update information within the respective sub frame of the second sub frame type and
perform LPC synthesis filtering on the excitation signal using the LPC information within the respective frame of the second frame type in order to acquire an LP synthesized signal segment for the sub portion of the time segment associated with the respective sub frame of the second sub frame type, and

perform time-domain aliasing cancellation within temporarily overlapping window portions at boundaries between time segments of immediately consecutive ones of frames of the first frame type and sub portions of time segments, which are associated with sub frames of the first sub frame type, to reconstruct the information signal thereacross, and
if the previous frame is of the first frame type or of the second frame type with the last sub frame thereof being of the first sub frame type, and the current frame is of the second frame type with the first sub frame thereof being of the second sub frame type, derive a first forward aliasing cancellation synthesis signal from the forward aliasing cancellation data and add the first forward aliasing cancellation synthesis signal to the re-transformed signal segment within the previous time segment to reconstruct the information signal across the boundary between the previous and current frames, and
if the previous frame is of the second frame type with the first sub frame thereof being of the second sub frame type, and the current frame is of the first frame type or of the second frame type with the last sub frame thereof being of the first sub frame type, derive a second forward aliasing cancellation synthesis signal from the forward aliasing cancellation data and add the second forward aliasing cancellation synthesis signal to the re-transformed signal segment within the current time segment to reconstruct the information signal across the boundary between the previous and current time segments.

4. Decoder apparatus according to claim 3 , wherein the reconstructor is configured to
derive the first forward aliasing cancellation synthesis signal from the forward aliasing cancellation data by performing a re-transform on transform coefficient information comprised by the forward aliasing cancellation data or derive the second forward aliasing cancellation synthesis signal from the forward aliasing cancellation data by performing the re-transform on transform coefficient information comprised by the forward aliasing cancellation data.

5. Decoder apparatus according to claim 3 , wherein the second syntax portion comprises a first flag signaling as to whether forward aliasing cancellation data is present or not in the respective frame, and the parser is configured to perform the second selection depending on the first flag, and wherein the second syntax portion further comprises a second flag merely within frames of the second frame type, the second flag signaling as to whether the previous frame is of the first frame type or of the second frame type with the last sub frame thereof being of the first su

Assignees

• Fraunhofer Ges Forschung

Inventors

• Lecomte Jeremie
• Warmbold Patrick
• Bayer Stefan

Classifications

• G10L19/0212

  using orthogonal transformation · CPC title

• G10L19/20

  using sound class specific coding, hybrid encoders or object based coding · CPC title

• G10L19/005

  Correction of errors induced by the transmission channel, if related to the coding algorithm · CPC title

• G10L19/04 Primary

  using predictive techniques · CPC title

• G10L19/02

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title