Information signal encoding using a forward-adaptive prediction and a backwards-adaptive quantization

Patent metadata

Field	Value
Publication number	US-9754601-B2
Application number	US-30060207-A
Country	US
Kind code	B2
Filing date	Feb 28, 2007
Priority date	May 12, 2006
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A very coarse quantization exceeding the measure determined by the masking threshold without or only very little quality losses is enabled by quantizing not immediately the prefiltered signal, but a prediction error obtained by forward-adaptive prediction of the prefiltered signal. Due to the forward adaptivity, the quantizing error has no negative effect on the prediction on the decoder side.

First claim

The invention claimed is:

1. An apparatus for encoding an information signal into an encoded information signal, wherein the apparatus is configured to
determine one or more first linear prediction coefficients so as to define a transfer function which approximates an inverse of a psycho-perceptibility motivated threshold;
filter the information signal using the one or more first linear prediction coefficients, thereby attaining a prefiltered signal;
determine one or more second linear prediction coefficients based on the prefiltered signal;
predict the prefiltered signal using the one or more second linear prediction coefficients to attain a predicted signal and a prediction error for the prefiltered signal;
quantize the prediction error for attaining a quantized prediction error,
form, based on the quantized prediction error and the predicted signal, a reconstructed signal and perform the prediction of the prefiltered signal based on the reconstructed signal; and
encode into the encoded information signal the one or more first linear prediction coefficients, the one or more second linear prediction coefficients and the quantized prediction error,
wherein the information signal is an audio signal,
wherein the apparatus comprises a computer.

2. The apparatus according to claim 1 , wherein the apparatus is implemented to quantize the prediction error via a quantizing function, which maps unquantized values of the prediction error to quantizing indices of quantizing stages, and whose course below a threshold is steeper than above a threshold.

3. The apparatus according to claim 1 , wherein the apparatus is implemented to attain a quantizing stage height Δ(n) of the quantizing function in a backward-adaptive manner from the quantized prediction error.

4. The apparatus according to claim 1 , wherein the apparatus is implemented such that unquantized values of the prediction error are quantized via clipping by the quantizing function, which maps the unquantized values of the prediction error to quantizing indices of a constant and limited first number of quantizing stages for attaining the quantized prediction error.

5. The apparatus according to claim 4 , wherein the apparatus is implemented to attain a quantizing stage height Δ(n) of the quantizing function for quantizing a value (r(n)) of the prediction error in a backward-adaptive manner of two past quantizing indices i c (n−1) and i c (n−2) of the quantized prediction error according to Δ(n)=βΔ(n−1)+δ(n), with βε[0.0;1.0], δ(n)=δ 0 for |i c (n−1)+i c (n−2)|≦I and δ(n)=δ 1 for |i c (n−1)+i c (n−2)|>I with constant parameters δ 0 , δ 1 , I, wherein Δ(n−1) represents a quantizing stage height attained for quantizing a previous value of the prediction error.

6. The apparatus according to claim 4 , wherein the apparatus is implemented to quantize the prediction error in a nonlinear manner.

7. The apparatus according to claim 4 , wherein the constant and limited first number is 3.

8. The apparatus according to claim 1 , wherein the apparatus is implemented to determine the psycho-perceptibility motivated threshold in a block-wise manner from the information signal.

9. The apparatus according to claim 1 , wherein the apparatus is configured to encode the one or more first linear prediction coefficients in a line spectral frequency domain.

10. The apparatus according to claim 1 , wherein the apparatus is implemented to determine the psycho-perceptibility motivated threshold in a block-wise manner and to represent the psycho-perceptibility motivated threshold in filter coefficients, to subject the filter coefficients to a prediction and to subject a filter coefficient residual signal resulting from the prediction to a quantization via a further quantizing function, which maps the unquantized values of the filter coefficient residual signal to quantizing indices of quantizing stages, and whose course below a further threshold is steeper than above the further threshold, for attaining a quantized filter coefficient residual signal, wherein the apparatus is configured to also encode into encoded information signal the quantized filter coefficient residual signal.

11. The apparatus according to claim 10 , wherein the apparatus is implemented such that the unquantized values of the filter coefficient residual signal are quantized via clipping by the further quantizing function, which maps the unquantized values of the filter coefficient residual signal to quantizing indices of a constant and limited second number of quantizing stages.

12. The apparatus according to claim 11 , wherein the apparatus is implemented such that the prediction is performed in a backward-adaptive manner based on quantizing indices of the quantized filter coefficient residual signal.

13. The apparatus according to claim 10 , wherein the apparatus is implemented such that the prediction of the filter coefficients is performed by using a prediction filter with constant coefficients.

14. The apparatus according to claim 10 , wherein the apparatus is further implemented to subject the filter coefficients for representing the psycho-perceptibility motivated threshold to a subtraction with a constant value, prior to subjecting the filter coefficients to prediction.

15. The apparatus according to claim 1 , wherein the apparatus is implemented to encode into the encoded information signal the one or more second linear prediction coefficients in LSF domain.

16. A method for encoding an information signal into an encoded information signal, comprising:
determine one or more first linear prediction coefficients so as to define a transfer function which approximates an inverse of a psycho-perceptibility motivated threshold;
filtering the information signal using the one or more first linear prediction coefficients so as to attain a prefiltered signal;
determining one or more second linear prediction coefficients based on the prefiltered signal;
predicting the prefiltered signal using the one or more second linear prediction coefficients to attain a predicted signal and a prediction error for the prefiltered signal;
quantizing the prediction error to attain a quantized prediction error;
forming, based on the quantized prediction error and the predicted signal, a reconstructed signal and performing the prediction of the prefiltered signal based on the reconstructed signal; and
encoding into the encoded information signal the one or more first linear prediction coefficients, the one or more second linear prediction coefficients and the quantized prediction error,
wherein the information signal is an audio signal.

17. A non-transitory computer-readable medium having stored thereon a computer program with a program code for performing a method according to claim 16 .

Assignees

• Hirschfeld Jens
• Schuller Gerald
• Lutzky Manfred
• Kraemer Ulrich
• Wabnik Stefan
• Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E V

Inventors

• Hirschfeld Jens
• Schuller Gerald
• Lutzky Manfred
• Kraemer Ulrich
• Wabnik Stefan

Classifications

• G10L19/035

  Scalar quantisation · CPC title

• G10L19/0017 Primary

  Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error (G10L19/24 takes precedence) · CPC title

• G10L19/06 Primary

  Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients · CPC title

• G10L19/032

  Quantisation or dequantisation of spectral components · CPC title

• H04N19/80

  Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation (H04N19/635, H04N19/86 take precedence) · CPC title