[FFmpeg-user] Decimation with ppsrc=1 malfunctions

Paul B Mahol onemda at gmail.com
Sun Dec 27 20:37:25 EET 2020

On Sun, Dec 27, 2020 at 7:33 PM pdr0 <pdr0 at shaw.ca> wrote:

> One issue is scene change is still active. When you crop to a region of
> interest, a small change is effectively a larger % change. eg. The delta
> between 1020 and 1021 is large when head is going up. If you disable scene
> change, you get set intervals, it's no longer adaptive by scene change.
> -filter_complex "[0:0][1:0]decimate='ppsrc=1':scthresh=0"
> Drops become regular 1012,1017,1022,1027,1032
> Other differences are preprocessed.mkv is a lossy version and encoded
> progressively instead of interlaced or mbaff. There are motion vectors that
> cross fields that shouldn't, so you get motion when you shouldn't when you
> examine individual fields. ie. Fields are "muddied" in preprocessed.mkv .
> Also the chroma encoding is different when you encode progressively. You
> can
> see the colored edges are different on some fields. You can set chroma=0 to
> disable, or use a proper prepreprocessed version (Lossless and encoded with
> mbaff)
> These latter two aren't the explanation in this specific case, but you
> should test with original source, or lossless versions

Exactly I completely overlooked this fact.

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