Video Decoding with Reduced Complexity Deblocking
A method and apparatus for decoding a video comprising a plurality of frames. Each frame was encoded in a plurality of blocks of pixels, using a predictive algorithm with deblocking inside the prediction loop. A first deblocking filter was applied by the encoder at boundaries between adjacent blocks, and the output of the deblocking filter was used to provide a reference frame for the predictive algorithm. The decoding comprises: reconstructing a frame of the video, to produce a reconstructed frame; applying a second deblocking filter at some block-boundaries in the reconstructed frame; and skipping deblocking-filtering at other block-boundaries in the reconstructed frame, even though deblocking was applied at those block-boundaries by the encoder.
1 . A method of decoding a video comprising a plurality of frames, each of which was encoded in a plurality of blocks of pixels, which encoding used a predictive algorithm with deblocking inside the prediction loop, wherein a first deblocking filter was applied by the encoder at boundaries between adjacent blocks, and the output of the deblocking filter was used to provide a reference frame for the predictive algorithm,
the decoding method comprising:
reconstructing a frame of the video, to produce a reconstructed frame;
applying a second deblocking filter at some block-boundaries in the reconstructed frame; and
skipping deblocking-filtering at other block-boundaries in the reconstructed frame, even though deblocking was applied at those block-boundaries by the encoder.
2 . The method of claim 1 , wherein the reconstructed frame is a reference frame, and the decoding method further comprises using the reconstructed reference frame in the predictive algorithm to reconstruct another frame.
3 . The method of claim 1 , wherein the second deblocking filter is applied at a boundary between two macroblocks and deblocking-filtering is skipped for block-boundaries within at least one of the macroblocks.
4 . The method of claim 1 , comprising applying deblocking to a greater proportion of the block-boundaries when reconstructing the luminance component of a frame, compared with reconstructing the chrominance component of the frame.
5 . The method of claim 1 , comprising:
counting the number of successive reference frames for which deblocking has been skipped at some or all of the block-boundaries;
detecting when this number exceeds a threshold; and
in response, increasing the proportion of block-boundaries to which deblocking is applied when reconstructing a subsequent frame.
6 . The method of claim 1 , comprising applying deblocking to a greater proportion of the block-boundaries when reconstructing an intra-coded macroblock, compared with reconstructing an inter-coded macroblock.
7 . The method of claim 1 , wherein the video is encoded in conformance with the H.264 standard.
8 . The method of claim 1 , wherein the first deblocking filter and the second deblocking filter are identical.
9 . A method of decoding a video encoded in conformance with the H.264 standard, comprising:
applying a deblocking filter at some block-boundaries in a reconstructed frame; and
skipping deblocking for some other block-boundaries in the reconstructed frame, even though deblocking was applied at those block-boundaries by the encoder.
10 . The method of claim 9 , comprising applying deblocking to a greater proportion of the block-boundaries when reconstructing the luminance component of a frame, compared with reconstructing the chrominance component of the frame.
11 . The method of claim 9 , comprising:
counting the number of successive reference frames for which deblocking has been skipped at some or all of the block-boundaries;
detecting when this number exceeds a threshold; and
in response, increasing the proportion of block-boundaries to which deblocking is applied when reconstructing a subsequent frame.
12 . The method of claim 9 , comprising applying deblocking to a greater proportion of the block boundaries when reconstructing an intra-coded macroblock, compared with reconstructing an inter-coded macroblock.
13 . A computer program comprising computer program code means adapted to perform all the steps of claim 1 when said program is run on a physical computing device.
14 . A computer program as claimed in claim 13 embodied on a non-transitory computer readable medium.
15 . Video decoding apparatus adapted to decode a video comprising a plurality of frames, each of which was encoded in a plurality of blocks of pixels, which encoding used a predictive algorithm with deblocking inside the prediction loop, wherein a first deblocking filter was applied by the encoder at boundaries between adjacent blocks, and the output of the deblocking filter was used to provide a reference frame for the predictive algorithm,
the video decoding apparatus comprising:
a frame reconstruction unit, adapted to reconstruct a frame of the video, to produce a reconstructed frame; and
a deblocking-filter unit, adapted to:
apply a second deblocking filter at some block-boundaries in the reconstructed frame; and
skip deblocking-filtering at other block-boundaries in the reconstructed frame, even though deblocking was applied at those block-boundaries by the encoder.