Low bitrate audio encoding/decoding scheme having cascaded switches
An audio encoder has a first information sink oriented encoding branch, a second information source or SNR oriented encoding branch, and a switch for switching between the first encoding branch and the second encoding branch, wherein the second encoding branch has a converter into a specific domain different from the spectral domain, and wherein the second encoding branch furthermore has a specific domain coding branch, and a specific spectral domain coding branch, and an additional switch for switching between the specific domain coding branch and the specific spectral domain coding branch. An audio decoder has a first domain decoder, a second domain decoder for decoding a signal, and a third domain decoder and two cascaded switches for switching between the decoders.
1. Audio decoder for decoding an encoded audio signal, the encoded audio signal comprising a first encoded signal, a first processed signal in a second domain, and a second processed signal in a third domain, wherein the first encoded signal, the first processed signal, and the second processed signal are related to different time portions of a decoded audio signal, and wherein a first domain, the second domain and the third domain are different from each other, the audio decoder comprising:
a first decoding branch for decoding the first encoded signal based on a first decoding algorithm;
a second decoding branch for decoding the first processed signal or the second processed signal, wherein the second decoding branch comprises:
a first inverse processing branch for inverse processing the first processed signal to acquire a first inverse processed signal in the second domain;
a second inverse processing branch for inverse processing the second processed signal to acquire a second inverse processed signal in the second domain;
a first combiner for combining the first inverse processed signal and the second inverse processed signal to acquire a combined signal in the second domain; and
a converter for converting the combined signal to the first domain; and
a second combiner for combining the converted signal in the first domain and the first decoded signal output by the first decoding branch to acquire the decoded audio signal in the first domain,
wherein the first decoding branch and the second decoding branch are operative to operate in a block wise manner, wherein a switching over action in the first combiner or the second combiner takes place, at the minimum, after a block of a predefined number of samples of a signal, the predefined number of samples forming a frame length for the corresponding combiner, and
wherein a size of the frame length for the second combiner is greater than the size of the frame length of the first combiner.
2. Audio decoder of the claim 1 , in which the first combiner or the second combiner comprises a switch comprising a cross fading functionality.
3. Audio decoder of claim 1 , in which the first domain is a time domain, the second domain is an LPC domain, the third domain is an LPC spectral domain, or the first encoded signal is encoded in a fourth domain, which is a time-spectral domain acquired by time/frequency converting a signal in the first domain.
4. Audio decoder in accordance with claim 1 , in which the first decoding branch comprises an inverse coder and a de-quantizer and a frequency domain time domain converter, or
the second decoding branch comprises an inverse coder and a de-quantizer in the first inverse processing branch or an inverse coder and a de-quantizer and an LPC spectral domain to LPC domain converter in the second inverse processing branch.
5. Audio decoder of claim 4 , in which the first decoding branch or the second inverse processing branch comprises an overlap-adder for performing a time domain aliasing cancellation functionality.
6. Audio decoder in accordance with claim 1 , in which the first decoding branch or the second inverse processing branch comprises a de-warper controlled by a warping characteristic comprised in the encoded audio signal.
7. Audio decoder in accordance with claim 1 , in which the encoded signal comprises, as side information, an indication whether a coded signal is to be coded by a first encoding branch or a second encoding branch or a first processing branch of the second encoding branch or a second processing branch of the second encoding branch, and
which further comprises a parser for parsing the encoded signal to determine, based on the side information, whether a coded signal is to be processed by the first decoding branch, or the second decoding branch, or the first inverse processing branch of the second decoding branch or the second inverse processing branch of the second decoding branch.
8. Audio decoder in accordance with claim 1 , wherein a minimum size of the frame length of the second combiner is 2048 or 1024 samples.
9. Audio decoder in accordance with claim 1 , wherein a minimum size of the frame length of the first combiner is one of 1024, 512, 256, and 128 samples.
10. Audio decoder in accordance with claim 1 , wherein a minimum size of the frame length of the second combiner is in integer multiple of the minimum size of the frame length of the first combiner.
11. Audio decoder in accordance with claim 1 , wherein the integer multiple is at least greater or equal to one of 2, 4, and 16.
12. Method of decoding an encoded audio signal, the encoded audio signal comprising a first encoded signal, a first processed signal in a second domain, and a second processed signal in a third domain, wherein the first encoded signal, the first processed signal, and the second processed signal are related to different time portions of a decoded audio signal, and wherein a first domain, the second domain and the third domain are different from each other, comprising:
decoding, by a first decoding branch, the first encoded signal based on a first decoding algorithm;
decoding, by a second decoding branch, the first processed signal or the second processed signal,
wherein the decoding the first processed signal or the second processed signal comprises:
inverse processing, by a first inverse processing branch, the first processed signal to acquire a first inverse processed signal in the second domain;
inverse processing, by a second inverse processing branch, the second processed signal to acquire a second inverse processed signal in the second domain;
combining, by a first combiner, the first inverse processed signal and the second inverse processed signal to acquire a combined signal in the second domain; and
converting, by a converter, the combined signal to the first domain; and
combining, by a second combiner, the converted signal in the first domain and the decoded first signal to acquire the decoded audio signal in the first domain,
wherein at least one of the first decoding branch, the second decoding branch, the first inverse processing branch, the second inverse processing branch, the first combiner, the converter, and the second combiner comprises a hardware implementation,
wherein the first decoding branch and the second decoding branch are operative to operate in a block wise manner, wherein a switching over action in in the first combiner or the second combiner takes place, at the minimum, after a block of a predefined number of samples of a signal, the predefined number of samples forming a frame length for the corresponding combiner, and
wherein a size of the frame length for the second combiner is greater than the size of the frame length of the first combiner.
13. A non-transitory storage medium having stored thereon a computer program for performing, when running on the computer, the method of decoding an encoded audio signal, the encoded audio signal comprising a first encoded signal, a first processed signal in a second domain, and a second processed signal in a third domain, wherein the first encoded signal, the first processed signal, and the second processed signal are related to different time portions of a decoded audio signal, and wherein a first domain, the second domain and the third domain are different from each other, comprising:
first decoding the first encoded signal based on a first decoding algorithm;
second decoding the first processed signal or the second processed signal,
wherein the second decoding the first processed signal or the second processed signal comprises:
inverse processing the first processed signal to acquire a first inverse processed signal in the second domain;
inverse processing the second processed signal to acquire a second inverse processed signal in the second domain;
first combining the first inverse processed signal and the second inverse processed signal to acquire a combined signal in the second domain; and
converting the combined signal to the first domain; and
second combining the converted signal in the first domain and the decoded first signal to acquire the decoded audio signal in the first domain,
wherein the first decoding and the second decoding are operative to operate in a block wise manner, wherein a switching over action in the first or second combining takes place, at the minimum, after a block of a predefined number of samples of a signal, the predefined number of samples forming a frame length for the corresponding combining, and
wherein a size of the frame length for the second combining is greater than the size of the frame length of the first combining.