Refined block-based predictive coding and decoding of a picture
The refinement of block-based predictive coding and decoding of pictures as applicable in, e.g., hybrid video codecs, using additional reconstructed samples or residuals is described. An apparatus for block-based predictive decoding of a picture is described. The apparatus includes a combiner configured to combine a residual signal a predetermined block of the picture and a reference signal for the predetermined block so as to obtain a first spectrum, the residual signal correcting a prediction error of a prediction of the predetermined block of the picture; a reducer configured to perform thresholding on the first spectrum to obtain a second spectrum so that coefficients below a threshold value are set to a predefined value; an extractor configured to obtain from the second spectrum a modified version of the residual signal; and a reconstructor block configured to decode the predetermined block of the picture from the data stream on the basis of the modified version of the residual signal.
1. An apparatus for block-based predictive decoding of a picture, the apparatus comprising:
a processor and memory, the processor configured to:
decode, from a data stream, an index and a residual signal for a current block of the picture, the index indicating a threshold value for the current block, the residual signal for correcting a prediction error of a prediction signal that is derived for the current block;
modify an employed signal comprising at least one of the prediction signal and the residual signal, wherein the modified employed signal is obtained by:
comparing, for each coefficient position within a reference signal for the current block, a respective reference signal coefficient against the threshold value, and
when the respective reference signal coefficient is below the threshold value, setting a coefficient of the employed signal at that coefficient position to a predefined value; and
decode the current block from the data stream based on the modified employed signal.
2. The apparatus of claim 1 , wherein the processor is further configured to:
combine the employed signal and the reference signal so as to obtain a first set of coefficients;
set, at the corresponding coefficient position within the first set of coefficients, the coefficient to the predefined value, to obtain a modified first set of coefficients; and
obtain from the modified first set of coefficients the modified employed signal.
3. The apparatus of claim 2 , wherein the processor is further configured to:
perform a transform on a region composed of the prediction signal and the reference signal so as to obtain a first set of coefficients of the region; and
subject the modified first set of coefficients to a re-transform so as to obtain a modified version of the region including the modified prediction signal.
4. The apparatus of claim 1 , wherein the reference signal comprises a neighboring reconstructed residual.
5. The apparatus of claim 1 , wherein the threshold value is based on a quantization parameter associated with the residual signal.
6. A method for block-based predictive decoding of a picture, comprising:
decoding, from a data stream, an index indicating a threshold value and a residual signal for a current block of the picture, the residual signal correcting a prediction error of a prediction signal that is derived for the current block of the picture;
modifying an employed signal comprising at least one of the prediction signal and the residual signal, wherein the modified employed signal is obtained by:
comparing, for each coefficient position within a reference signal for the current block, a respective reference signal coefficient against the threshold value, and
when the respective reference signal coefficient is below the threshold value, setting a coefficient of the employed signal at that coefficient position to a predefined value; and
decoding the current block from the data stream based on the modified employed signal.
7. The method of claim 6 , wherein the reference signal comprises a neighboring reconstructed residual.
8. The method of claim 6 , wherein the threshold value is based on a quantization parameter associated with the residual signal.
9. An apparatus for block-based predictive encoding of a picture, the apparatus comprising:
a processor and memory, the processor configured to:
encode a residual signal for a current block of the picture and an index indicating a threshold value for the current block into a data stream, the residual signal for correcting a prediction error of a prediction signal for the current block;
modify an employed signal comprising at least one of the prediction signal and the residual signal, wherein the modified employed signal is obtained by:
comparing, for each coefficient position within a reference signal for the current block, a respective reference signal coefficient against the threshold value, and
when the respective reference signal coefficient is below the threshold value, setting a coefficient of the employed signal at that coefficient position to a predefined value; and
encode the current block to the data stream based on the modified employed signal.
10. The apparatus of claim 9 , wherein the processor is further configured to:
combine the employed signal and the reference signal so as to obtain a first set of coefficients;
set, at the corresponding coefficient position within the first set of coefficients, the coefficient to the predefined value, to obtain a modified first set of coefficients; and
obtain from the modified first set of coefficients the modified employed signal.
11. The apparatus of claim 10 , wherein the processor is further configured to:
perform a transform on a region composed of the prediction signal and the reference signal so as to obtain a first set of coefficients of the region; and
subject the modified first set of coefficients to a re-transform so as to obtain a modified version of the region including the modified prediction signal.
12. The apparatus of claim 9 , wherein the threshold value is based on a quantization parameter associated with the residual signal.
13. A method for block-based predictive encoding of a picture, comprising:
encoding a residual signal for a current block of the picture and an index indicating a threshold value for the current block into a data stream, the residual signal for correcting a prediction error of a prediction signal for the current block of the picture;
modifying an employed signal comprising at least one of the prediction signal and the residual signal, wherein the modified employed signal is obtained by:
comparing, for each coefficient position within a reference signal for the current block, a respective reference signal coefficient against the threshold value, and
when the respective reference signal coefficient is below the threshold value, setting a coefficient of the employed signal at that coefficient position to a predefined value; and
encoding the current block to the data stream based on the modified employed signal.
14. The method of claim 13 , wherein the threshold value is based on a quantization parameter associated with the residual signal.