Methods and apparatus for improving high frequency reconstruction of audio and speech signals
AssigneeCoding Technologies AB
InventorsKristofer Kjörling, Per Ekstrand, Holger Hörich
Life of this patent
Estimating the term…
Abstract
The present invention proposes a new method and a new apparatus for enhancement of audio source coding systems utilizing high frequency reconstruction (HFR). It utilizes a detection mechanism on the encoder side to assess what parts of the spectrum will not be correctly reproduced by the HFR method in the decoder. Information on this is efficiently coded and sent to the decoder, where it is combined with the output of the HFR unit.
Claims30
An encoder apparatus comprising:
- an encoder for encoding an audio signal to obtain an encoded signal, the encoded signal being intended for decoding using a high frequency regeneration technique, which is suited for generating frequency components above a predetermined frequency based on frequency components below the predetermined frequency, the encoder further comprising:
- a coding algorithm for producing an encoded input signal, which comprises a representation of an input signal that is coded using the coding algorithm, and that represents a frequency content of the audio signal below the predetermined frequency;
- a high frequency regenerator for performing the high frequency regeneration technique on the input signal or a coded and decoded version thereof to obtain a regenerated signal having frequency components above the predetermined frequency;
- a detector for detecting differences between the regenerated signal and the audio signal, which are above a significance threshold;
- a describer for describing detected differences to obtain additional information;
- and
- a combiner for combining the encoded input signal and the additional information to produce the encoded signal, wherein the encoder, the coding algorithm, the high frequency regenerator, the detector, the describer or the combiner comprises a hardware implementation.
Decoder for decoding an encoded signal, the encoded signal including an encoded input signal representing a frequency content of an original audio signal below a predetermined frequency, and an additional information, the decoder comprising:
- a coding algorithm for decoding the encoded input signal to produce a decoded input signal;
- a reconstructor for reconstructing differences between the original audio signal and a regenerated signal based on the additional information, wherein a difference includes spectral lines in a specified frequency region and the additional information related to the specific frequency region, wherein the reconstructor is arranged for generating a spectral line in the specified region in response to the additional information;
- a high frequency generator for performing a high frequency regeneration technique to obtain the regenerated signal;
- and
- a producer for producing a high frequency regenerated audio signal based on the decoded input signal, the reconstructed differences and the regenerated signal, wherein the coding algorithm, the reconstructor, the high frequency generator or the producer comprises a hardware implementation.
Method for encoding an audio signal to obtain an encoded signal, the encoded signal being intended for decoding using a high frequency regeneration technique, which is suited for generating frequency components above a predetermined frequency based on frequency components below the predetermined frequency, the method comprising:
- providing an encoded input signal, which is a coded representation of an input signal, the input signal being coded using a coding algorithm, and representing a frequency content of the audio signal below the predetermined frequency;
- performing the high frequency regeneration technique on the input signal or a coded and decoded version thereof to obtain a regenerated signal having frequency components above the predetermined frequency;
- detecting differences between the regenerated signal and the audio signal, which are above a significance threshold;
- describing detected differences to obtain additional information;
- and
- combining the encoded input signal and the additional information to produce the encoded signal.
Method for decoding an encoded signal, the encoded signal including an encoded input signal representing a frequency content of an original audio signal below a predetermined frequency, the encoding being performed using a coding algorithm, and additional information describing differences between a regenerated signal and the original audio signal, the regenerated signal being generated by a high frequency regenerating technique from the input signal or a coded and decoded version thereof, the method comprising:
- obtaining a decoded input signal, which is produced by decoding the encoded input signal in accordance with the coding algorithm;
- reconstructing differences based on the additional information, wherein a difference includes spectral lines in a specified frequency region and the additional information relates to the specific frequency region, wherein the reconstructing differences comprises generating a spectral line in the specified region in response to the additional information;
- performing a high frequency regeneration technique similar to the high frequency regeneration technique for obtaining the differences to obtain the regenerated signal;
- producing a high frequency regenerated audio signal based on the decoded input signal, the reconstructed differences and the regenerated signal.
A non-transitory computer-readable medium encoded with a computer program for performing a method for encoding an audio signal to obtain an encoded signal, the encoded signal being intended for decoding using a high frequency regeneration technique, which is suited for generating frequency components above a predetermined frequency based on frequency components below the predetermined frequency, the method comprising:
- providing an encoded input signal, which is a coded representation of an input signal, the input signal being coded using a coding algorithm, and representing a frequency content of the audio signal below the predetermined frequency;
- performing the high frequency regeneration technique on the input signal or a coded and decoded version thereof to obtain a regenerated signal having frequency components above the predetermined frequency;
- detecting differences between the regenerated signal and the audio signal, which are above a significance threshold;
- describing detected differences to obtain additional information;
- and
- combining the encoded input signal and the additional information to produce the encoded signal, when the computer program runs on a computer.
A non-transitory computer-readable medium encoded with a computer program for performing a method for decoding an encoded signal, the encoded signal including an encoded input signal representing a frequency content of an original audio signal below a predetermined frequency, the encoding being performed using a coding algorithm, and additional information describing differences between a regenerated signal and the original audio signal, the regenerated signal being generated by a high frequency regenerating technique from the input signal or a coded and decoded version thereof, the method comprising:
- obtaining a decoded input signal, which is produced by decoding the encoded input signal in accordance with the coding algorithm;
- reconstructing differences based on the additional information, wherein a difference includes spectral lines in a specified frequency region and the additional information relates to the specific frequency region, wherein the reconstructing differences comprises generating a spectral line in the specified region in response to the additional information;
- performing a high frequency regeneration technique similar to the high frequency regeneration technique for obtaining the differences to obtain the regenerated signal;
- producing a high frequency regenerated audio signal based on the decoded input signal, the reconstructed differences and the regenerated signal, when the computer program runs on a computer.
Dependencies are inferred from the claim text.