[FFmpeg-user] minterpolate ...for Paul

[Paul B Mahol]

On Fri, Jan 29, 2021 at 2:01 AM pdr0 <pdr0 at shaw.ca> wrote:

> Mark Filipak (ffmpeg) wrote
> > I've never heard of "optical flow errors". What could they be? (Got any
> > links to
> > explanations?)
>
> The artifacts in your video are optical flow errors :)
>
> If you've ever used it - you'd recognize these artifacts. There are very
> common
>
>
>
> There are about a dozen prototypical "fail" categories or common errors
> that
> plague all types of optical flow
>
> These are errors either of motion vectors, or object flow (object
> boundaries
> or "masks"), occlusion errors.
>
> Internet is full of examples, explanations. The topic is rather large, just
> search google, there is lots of info. If you have a specific question then
> ask.
>
> Sometimes you get clean interpolated frame results;  but sometimes there
> are
> massive distracting errors. It varies by situation and sources.
>
> Your example has one of the common categories of "fail" where there are
> repeating patterns and textures. It falls under the "Picket Fence" fail . A
> prototypical tracking or dolly shot by a picket fence, or brick wall will
> come up with interpolation errors
>
> The peripheral edges error are common because there is less data beyond the
> periphery of the frame, for n-1, n+1 and the motion vectors are less
> accurate compared to the center of the frame
>
> Another common one is when objects pass over another. The flow masks aren't
> perfect and you end up with blobby edge artifacts around objects
>
>
>
>
>
>
>
> >>...For artifacts around frame edges, letterbox edges usually some form
> >> of padding is used. I don't think ffmpeg minterpolate has those.
> >
> > I've done that. The result was just okay. The slight riffling on the
> frame
> > boundaries during camera
> > panning isn't all that objectionable to me. It occurs to me that
> > minterpolute could queue frames and
> > look 'forward' to later frames in order to resolve boundary macroblock
> > artifacts -- afterall, it has
> > the motion vectors, eh?
>
> Some algorithms can use N-3, N-2, N-1, N, N+1, N+2, N+3, I don't think
> minterpolate can.  More is not always better. Often you get more
> contamination with a larger "window"
>
> Sometimes just changing the blocksize can produce better (or worse)
> results.
> The problem is ffmpeg minterpolate is soooo slow, and you have no usable
> preview. Some of the other methods mentioned earlier do have previews -  so
> you can tweak settings, preview, readjust etc....
>
>
Why you ignore fact that libavfilter also allows usable preview and
readjust of parameters.

Amount of false information propagation here is astounding.


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