Enhanced intra prediction with bilateral filter
A method of video decoding includes receiving a bitstream that comprises coded information of one or more pictures. The coded information indicates an intra prediction of a current block. The method also includes: enabling a reference sample filtering with a bilateral filter when the current block satisfies one or more conditions associated with the reference sample filtering; applying the reference sample filtering with the bilateral filter on reference samples of the current block to obtain filtered reference samples when the reference sample filtering with the bilateral filter is enabled; and reconstructing one or more samples of the current block according to the intra prediction using the filtered reference samples.
1 . A method of video decoding, comprising:
receiving a bitstream that comprises coded information of one or more pictures, the coded information indicating an intra prediction of a current block;
determining whether a reference sample filtering is enabled for the current block based on one or more conditions associated with the reference sample filtering;
applying the reference sample filtering with a bilateral filter on reference samples of the current block to obtain filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) a block content variance of the current block is equal to or greater than a first threshold value; and
reconstructing one or more samples of the current block according to the intra prediction using the filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) the block content variance of the current block is equal to or greater than the first threshold value.
2 . The method of claim 1 , wherein when the current block fails to satisfy the one or more conditions, the method further comprises:
reconstructing the one or more samples of the current block according to the intra prediction using the reference samples without filtering.
3 . The method of claim 1 , wherein the one or more conditions comprise at least one of:
a prediction mode of the intra prediction is not a vertical mode;
the prediction mode of the intra prediction is not a horizontal mode;
the prediction mode uses integer position reference samples;
no multiple reference line intra prediction is applied;
no sub-partition prediction is applied;
a block size of the current block is larger than a threshold;
the current block is a prediction block within luma component; and/or
a flag associated with the current block is decoded from the bitstream and indicates a use of the bilateral filter.
4 . The method of claim 1 , wherein the reference sample filtering includes a single filtering stage of the bilateral filter.
5 . The method of claim 1 , wherein the reference sample filtering uses the bilateral filter and a predefined filter that are connected in series.
6 . The method of claim 1 , wherein the reference sample filtering uses the bilateral filter and a predefined filter that are connected in parallel.
7 . The method of claim 6 , wherein the applying comprises:
applying the predefined filter when a block size of the current block is less than a second threshold value; and
applying the bilateral filter in the reference sample filtering when the block size of the current block is equal to or greater than the second threshold value.
8 . The method of claim 6 , wherein the applying comprises:
applying the predefined filter when the block content variance of the current block is less than the first threshold value; and
applying the bilateral filter when the block content variance of the current block is equal to or greater than the first threshold value.
9 . The method of claim 1 , wherein the reference sample filtering includes the bilateral filter and/or a predefined filter, and the method comprises:
applying the bilateral filter on the reference samples to obtain the filtered reference samples when the current block fails to satisfy the one or more conditions; and
applying the predefined filter on the reference samples to obtain the filtered reference samples when the current block satisfies the one or more conditions.
10 . The method of claim 1 , wherein the reference sample filtering includes the bilateral filter and/or a predefined filter, and the method comprises:
applying the bilateral filter on the reference samples to obtain first filtered reference samples;
reconstructing the one or more samples of the current block according to the intra prediction using the first filtered reference samples when the current block fails to satisfy the one or more conditions; and
reconstructing the one or more samples of the current block according to the intra prediction using second filtered reference samples when the current block satisfies the one or more conditions, the second filtered reference samples being obtained by applying the predefined filter on the first filtered reference samples.
11 . The method of claim 1 , wherein the reference sample filtering includes the bilateral filter and/or a predefined filter, and the method comprises:
applying the predefined filter on the reference samples to obtain intermediate filtered reference samples when the current block satisfies the one or more conditions;
copying the reference samples to be the intermediate filtered reference samples when the current block fails to satisfy the one or more conditions;
applying the bilateral filter on the intermediate filtered reference samples to obtain the filtered reference samples; and
reconstructing the current block according to the intra prediction using the filtered reference samples.
12 . The method of claim 1 , further comprising:
checking whether at least one of a decoder side intra mode derivation, a template-based intra mode derivation, and a gradient position dependent intra prediction is enabled; and
when at least one of the decoder side intra mode derivation, the template-based intra mode derivation, and the gradient position dependent intra prediction is enabled, determining whether the current block satisfies the one or more conditions associated with the reference sample filtering including the bilateral filter.
13 . The method of claim 1 , further comprising:
decoding a flag from the bitstream, the flag being one of a sequence parameter set (SPS) level, a video parameter set (VPS) level, a picture parameter set (PPS) level, an adaptation parameter set (APS) level, a picture header level, a slice header level and/or a block level; and
applying the reference sample filtering with the bilateral filter on the reference samples to obtain the filtered reference samples when the flag indicates a usage of the reference sample filtering with the bilateral filter.
14 . A method of video encoding, comprising:
determining to encode a current block using an intra prediction;
determining whether a reference sample filtering is enabled for the current block based on one or more conditions associated with the reference sample filtering;
applying the reference sample filtering with a bilateral filter on reference samples of the current block to obtain filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) a block content variance of the current block is equal to or greater than a first threshold value; and
encoding, using the intra prediction, the current block into coded information in a bitstream according to the filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) the block content variance of the current block is equal to or greater than the first threshold value.
15 . The method of claim 14 , wherein when the current block fails to satisfy the one or more conditions, the method further comprises:
encoding, using the intra prediction, the current block according to the reference samples without filtering.
16 . The method of claim 14 , wherein the one or more conditions comprise at least one of:
a prediction mode of the intra prediction is not a vertical mode;
the prediction mode of the intra prediction is not a horizontal mode;
the prediction mode uses integer position reference samples;
no multiple reference line intra prediction is applied;
no sub-partition prediction is applied;
a block size of the current block is larger than a threshold; and/or
the current block is a prediction block within luma component.
17 . The method of claim 14 , wherein the reference sample filtering includes a single filtering stage of the bilateral filter.
18 . The method of claim 14 , wherein the reference sample filtering uses the bilateral filter and a predefined filter that are connected in series.
19 . The method of claim 14 , wherein the reference sample filtering uses the bilateral filter and a predefined filter that are connected in parallel.
20 . A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform a method of encoding a bitstream comprising:
determining to encode a current block using an intra prediction;
determining whether a reference sample filtering is enabled for the current block based on one or more conditions associated with the reference sample filtering;
applying the reference sample filtering with a bilateral filter on reference samples of the current block to obtain filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) a block content variance of the current block is equal to or greater than a first threshold value;
encoding, using the intra prediction, the current block in the bitstream according to the filtered reference samples when (i) the one or more conditions indicate that the reference sample filtering is enabled and (ii) the block content variance of the current block is equal to or greater than the first threshold value; and
transmitting the encoded bitstream.