Position dependent intra prediction combination extended with angular modes

Patent metadata

Field	Value
Publication number	US-11611757-B2
Application number	US-201916371638-A
Country	US
Kind code	B2
Filing date	Apr 1, 2019
Priority date	Apr 2, 2018
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

Techniques are described of using Position Dependent Intra Prediction Combination (PDPC). A video coder such as a video encoder or a video decoder utilizes PDPC in cases where a current block intra mode predicted using an angular intra prediction mode.

First claim

What is claimed is:

1. A method of decoding video data, the method comprising:
determining a prediction block, which includes a plurality of prediction samples, for a current block based on an angular intra prediction mode that is not a DC, planar, horizontal, or vertical intra prediction mode;
modifying a prediction sample of the plurality of prediction samples of the prediction block to generate a modified prediction sample using Position Dependent Intra Prediction Combination (PDPC), wherein modifying the prediction sample comprises:
determining one or more reference samples that are external to the current block based on an angle of the angular intra prediction mode; and
modifying the prediction sample to generate the modified prediction sample based on the determined one or more reference samples; and

reconstructing a sample of the current block based on the modified prediction sample and a residual value,
wherein determining one or more reference samples that are external to the current block comprises:
determining, as part of using PDPC, a row that is above the current block;
determining, as part of using PDPC, an x-coordinate in the determined row,

wherein the x-coordinate in the determined row is based on the angle of the angular intra prediction mode; and
determining, as part of using PDPC, a reference sample of the one or more reference samples based on the determined row and the determined x-coordinate,

wherein determining, as part of using PDPC, the x-coordinate in the determined row comprises:
determining, as part of using PDPC, one of a cotangent or tangent of the angle of the angular intra prediction mode; and
determining, as part of using PDPC, the x-coordinate in the determined row based on one of the cotangent or tangent of the angle of the angular intra prediction mode, an x-coordinate of the prediction sample, and a y-coordinate of the prediction sample.

2. The method of claim 1 , wherein determining one or more reference samples that are external to the current block comprises determining the one or more reference samples having at least one of an x-coordinate and a y-coordinate that is different than at least one of the respective x-coordinate and y-coordinate of the prediction sample in the prediction block.

3. The method of claim 1 , wherein the x-coordinate in the determined row is based on an x-coordinate of the prediction sample and a y-coordinate of the prediction sample plus 1.

4. The method of claim 1 , wherein the reference sample is a first reference sample of the one or more reference samples, and wherein determining one or more reference samples that are external to the current block further comprises:
determining a column that is left of the current block;
determining a y-coordinate in the determined column, wherein the y-coordinate in the determined column is based on an x-coordinate of the prediction sample and a y-coordinate of the prediction sample plus 1; and
determining a second reference sample of the one or more reference samples based on the determined column and the determined y-coordinate.

5. A method of decoding video data, the method comprising:
determining a prediction block, which includes a plurality of prediction samples, for a current block based on an angular intra prediction mode that is not a DC, planar, horizontal, or vertical intra prediction mode;
modifying a prediction sample of the plurality of prediction samples of the prediction block to generate a modified prediction sample using Position Dependent Intra Prediction Combination (PDPC), wherein modifying the prediction sample comprises:
determining one or more reference samples that are external to the current block based on an angle of the angular intra prediction mode; and
modifying the prediction sample to generate the modified prediction sample based on the determined one or more reference samples; and

reconstructing a sample of the current block based on the modified prediction sample and a residual value,
wherein determining one or more reference samples that are external to the current block comprises:
determining, as part of using PDPC, a column that is left of the current block;
determining, as part of using PDPC, a y-coordinate in the determined column,

wherein the y-coordinate in the determined column is based on the angle of the angular intra prediction mode; and
determining, as part of using PDPC, a reference sample of the one or more reference samples based on the determined column and the determined y-coordinate; and

wherein determining, as part of using PDPC, the y-coordinate in the determined column comprises:
determining, as part of using PDPC, one of a cotangent or tangent of the angle of the angular intra prediction mode; and
determining, as part of using PDPC, the y-coordinate in the determined column based on one of the cotangent or tangent of the angle of the angular intra prediction mode, an x-coordinate of the prediction sample, and a y-coordinate of the prediction sample.

6. The method of claim 1 , wherein determining one or more reference samples that are external to the current block based on the angular intra prediction mode comprises:
determining a set of one or more samples based on the angular intra prediction mode; and
at least one of interpolating, rounding with offset, or rounding without offset the set of one or more samples to generate the one or more reference samples.

7. The method of claim 1 , wherein determining one or more reference samples that are external to the current block based on the angular intra prediction mode comprises:
determining that one or more samples external to the current block identified based on the angular intra prediction mode are not stored in a reference line buffer; and
determining the one or more reference samples based on a last reference sample stored in the reference line buffer.

8. The method of claim 1 , wherein modifying the prediction sample of the prediction block comprises modifying a first prediction sample of the prediction block, and wherein the one or more reference samples comprise a first set of one or more reference samples, the method further comprising:
determining, for a second prediction sample of the same prediction block, that at least one reference sample of a second set of one or more reference samples for the second prediction sample are not stored in a reference line buffer; and
one of not applying PDPC to the second prediction sample or applying PDPC using only reference samples available in reference line buffer.

9. The method of claim 1 , further comprising:
determining a plurality of weights based on at least one of the x- and y-coordinates of the prediction sample,
wherein modifying the prediction sample comprises modifying the prediction sample to generate the modified prediction sample based on the determined one or more reference samples, the determined weights, and the prediction sample.

10. A method of encoding video data, the method comprising:
determining a prediction block, which includes a plurality of prediction samples, for a current block based on an angular intra prediction mode that is not a DC, planar, horizontal, or vertical intra prediction mode;
modifying a prediction sample of the plurality of prediction samples of the prediction block to generate a modified prediction sample using Position Dependent Intra Prediction Combination (PDPC), wherein modifying the prediction sample comprises:
determining one or more reference samples that are external to the current block based on an angle of the angular intra prediction mode; and
modifying the prediction sample to generate the modified prediction sample based on the determined one or

Assignees

• Qualcomm Inc
• Qualcomm Incorproated

Inventors

• Van Der Auwera Geert
• Seregin Vadim
• Said Amir
• Karczewicz Marta

Classifications

• H04N19/59

  involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution · CPC title

• H04N19/132

  Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking · CPC title

• H04N19/139

  Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability · CPC title

• H04N19/105

  Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction · CPC title

• H04N19/176

  the region being a block, e.g. a macroblock · CPC title