Editing Compression artifact (section)

=== Video artifact reduction ===
{{Main article|Deblocking filter}}

The artifacts at block boundaries can be reduced by applying a [[deblocking filter]]. As in still image coding, it is possible to apply a deblocking filter to the decoder output as post-processing.

In motion-predicted video coding with a closed prediction loop, the encoder uses the decoder output as the prediction reference from which future frames are predicted. To that end, the encoder conceptually integrates a decoder. If this "decoder" performs a deblocking, the deblocked picture is then used as a reference picture for motion compensation, which improves coding efficiency by preventing a propagation of block artifacts across frames. This is referred to as an in-loop deblocking filter. Standards which specify an in-loop deblocking filter include [[VC-1]], [[H.263]] Annex J, [[H.264/AVC]], and [[H.265/HEVC]].