Audio encoding/decoding scheme having a switchable bypass

• US 8,959,017 B2
• Filed: 11/06/2012
• Issued: 02/17/2015
• Est. Priority Date: 07/17/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Grill, Bernhard, Bayer, Stefan, Fuchs, Guillaume, Geyersberger, Stefan, Geiger, Ralf, Hilpert, Johannes, Kraemer, Ulrich, Lecomte, Jeremie, Multrus, Markus, Neuendorf, Max, Popp, Harald, Rettelbach, Nikolaus, Bessette, Bruno, Gournay, Philippe, Salami, Redwan, LeFebvre, Roch, LaPierre, Jimmy
• Primary Examiner(s): Neway, Samuel G
• Application Number:
  US13/670,323
• Publication Number:
  US 20130066640A1
• Time in Patent Office: 833 Days
• Field of Search: 704500-504, 704200-230
• US Class Current: 704/205
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• 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 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: G10L 2019/0008 Algebraic codebooks

Abstract

An apparatus for encoding includes a first domain converter, a switchable bypass, a second domain converter, a first processor and a second processor to obtain an encoded audio signal having different signal portions represented by coded data in different domains, which have been coded by different coding algorithms. Corresponding decoding stages in the decoder together with a bypass for bypassing a domain converter allow the generation of a decoded audio signal with high quality and low bit rate.

Claims

1. An apparatus for encoding an audio signal to acquire an encoded audio signal, the audio signal being in a first domain, comprising:

a common preprocessor for compressing an input signal to obtain the audio signal;

a first domain converter for converting the audio signal from the first domain into a second domain;

a switchable bypass for bypassing the first domain converter or for causing a conversion of the audio signal by the first domain converter in response to a bypass switch control signal;

a second domain converter for converting an audio signal received from the switchable bypass or the first domain converter into a third domain, the third domain being different from the second domain;

a first processor for encoding the third domain audio signal in accordance with a first coding algorithm to acquire a first processed signal; and

a second processor for encoding the audio signal received from the first domain converter in accordance with a second coding algorithm being different from the first coding algorithm to acquire a second processed signal,

wherein the encoded signal for a portion of the audio signal either comprises the first processed signal or the second processed signal.

2. The apparatus in accordance with claim 1 in which the first domain converter comprises an LPC analysis filter for LPC filtering the audio signal to acquire an LPC residual signal and LPC parameter data.

3. The apparatus in accordance with claim 1 in which the second domain converter comprises a time-frequency converter for converting an input signal into a spectral representation thereof.

4. The apparatus in accordance with claim 1 in which the second processor is operative to generate an encoded output signal so that the encoded output signal is in the same domain as an input signal into the second processor.

5. The apparatus in accordance with claim 1 in which the first processor comprises a quantizer and an entropy encoder and in which the second processor comprises a code book-based source encoder.

6. The apparatus in accordance with claim 1 in which the first processor is based on an information sink model and the second processor is based on an information source model.

7. The apparatus in accordance with claim 1 further comprising a switching stage connected between an output of the first domain converter and an input of the second domain converter and an input of the second processor,

wherein the switching stage is adapted to switch between the input of the second domain converter and the input of the second processor in response to a switching stage control signal.

8. The apparatus in accordance with claim 1 in which an output of the switchable bypass is connected to an output of the first domain converter and an input of the switchable bypass is connected to an input into the first domain converter.

9. The apparatus in accordance with claim 1, further comprising a signal classifier for controlling the switchable bypass for a portion of the audio signal depending on an analysis result for the portion of the audio signal.

10. The apparatus in accordance with claim 1 in which the second domain converter is operative to convert an input signal in a block-based way and in which the second domain converter is operative to perform a block-based switching in response to an audio signal analysis so that the second domain converter is controlled in that blocks of different lengths are converted depending on the content of the audio signal.

11. A method of encoding an audio signal to acquire an encoded audio signal, the audio signal being in a first domain, comprising:

compressing an input signal to obtain the audio signal;

converting the audio signal from the first domain into a second domain;

bypassing converting the audio signal from the first domain into a second domain or causing a conversion of the audio signal from the first domain into a second domain in response to a bypass switch control signal;

converting a bypassed audio signal or an audio signal in the second domain into a third domain, the third domain being different from the second domain;

encoding the third domain audio signal generated by converting the bypassed audio signal or the audio signal in the second domain in accordance with a first coding algorithm to acquire a first processed signal; and

encoding the audio signal in the second domain in accordance with a second coding algorithm being different from the first coding algorithm to acquire a second processed signal,

wherein the encoded signal for a portion of the audio signal either comprises the first processed signal or the second processed signal.

12. An apparatus for decoding an encoded audio signal, the encoded audio signal comprising a first processed signal being in a third domain and a second processed signal being in a second domain, wherein the second domain and the third domain are different from each other, comprising:

a first inverse processor for inverse processing the first processed signal;

a second inverse processor for inverse processing the second processed signal;

a second converter for domain converting the first inverse processed signal from the third domain into a different domain;

a first converter for converting the second inverse processed signal into a first domain or for converting the first inverse processed signal, which was converted into a different domain, into the first domain when the different domain is not the first domain;

a bypass for bypassing the first converter when the different domain is the first domain; and

a common postprocessor for generating a decoded audio signal.

13. The apparatus in accordance with claim 12, further comprising a combiner for combining an output of the first converter and an output of the bypass to acquire a combined decoded audio signal.

14. The apparatus for decoding in accordance with claim 12, further comprising an input interface for extracting, from an encoded audio signal, the first processed signal, the second processed signal and the control signal indicating whether for a certain first inverse processed signal, the first converter is to be bypassed by the bypass or not.

15. The apparatus for decoding in accordance with claim 12 in which the first converter comprises a linear prediction coding (LPC) synthesis stage, and

wherein the second converter comprises a spectral-time converter for converting a spectral representation of an audio signal into a time representation of the audio signal.

16. The apparatus for decoding in accordance with claim 12 in which the first inverse processor comprises an entropy-decoder and a de-quantizer and in which the second inverse processor comprises the code book-based source decoder.

17. The apparatus for decoding in accordance with claim 12 in which the second converter is operative to perform a synthesis filtering operation such as an inverse time warped modified discrete cosine transform filtering operation controllable by additional information comprised by the encoded audio signal.

18. A method of decoding an encoded audio signal, the encoded audio signal comprising a first processed signal being in a third domain and a second processed signal being in a second domain, wherein the second domain and the third domain are different from each other, comprising:

inverse processing the first processed signal;

inverse processing the second processed signal;

second domain converting the first inverse processed signal from the third domain into a different domain;

first domain converting the second inverse processed signal into a first domain or converting the first inverse processed signal into the first domain when the different domain is not the first domain;

bypassing first domain converting when the different domain is the first domain; and

performing a common postprocessing for generating a decoded audio signal.

19. A non-transitory computer readable medium having stored thereon a computer program for performing, when running on a computer, a method of encoding an audio signal to acquire an encoded audio signal, the audio signal being in a first domain, comprising:

compressing an input signal to obtain the audio signal;

converting the audio signal from the first domain into a second domain;

bypassing converting the audio signal from the first domain into a second domain or causing a conversion of the audio signal from the first domain into a second domain in response to a bypass switch control signal;

converting a bypassed audio signal or an audio signal in the second domain into a third domain, the third domain being different from the second domain;

encoding the third domain audio signal generated by converting the bypassed audio signal or the audio signal in the second domain in accordance with a first coding algorithm to acquire a first processed signal; and

encoding the audio signal in the second domain in accordance with a second coding algorithm being different from the first coding algorithm to acquire a second processed signal,

wherein the encoded signal for a portion of the audio signal either comprises the first processed signal or the second processed signal.

20. A non-transitory computer readable medium having stored thereon a computer program for performing, when running on a computer, a method of decoding an encoded audio signal, the encoded audio signal comprising a first processed signal being in a third domain and a second processed signal being in a second domain, wherein the second domain and the third domain are different from each other, comprising:

inverse processing the first processed signal;

inverse processing the second processed signal;

second domain converting the first inverse processed signal from the third domain into a different domain;

first domain converting the second inverse processed signal into a first domain or converting the first inverse processed signal into the first domain when the different domain is not the first domain; and

bypassing first domain converting when the different domain is the first domain; and

performing a common postprocessing for generating a decoded audio signal.