[FFmpeg-devel] [PATCH] lavfi/bwdif: remove interpolated sample clipping

[Paul B Mahol]

On Sun, Jul 2, 2023 at 6:57 PM Lynne <dev at lynne.ee> wrote:

> Jul 2, 2023, 18:54 by dev at lynne.ee:
>
> > The issue is that clipping the interpolated temporal sample against
> > the spatially predicted sample causes artifacts to appear.
> >
> > Discovered while writing the Vulkan version (where I omitted the
> > same check).
> >
> > The clipping in the code is carried over from yadif. Removing the
> > same code in yadif does not make any difference to the output.
> > I think that the check was simply ill-adapted to the new prediction
> > code and does more harm.
> >
> > I tested replacing the range clip with only an FFMAX, and only an
> > FFMIN, but in both cases, artifacts still appeared.
> >
> > Test sample 1:
> https://files.lynne.ee/testsamples/mbaff_1080i60_idx.mkvTest sample 2:
> https://files.lynne.ee/testsamples/mbaff_bdmv_1080i60_8slice.mkv
> >
> > Command line:
> > ./ffmpeg_g -cpuflags 0 -i <INPUT> -vf bwdif=mode=send_field -c:v
> rawvideo -y <OUTPUT>.nut
> > Make sure to disable the assembly.
> >
> > Comparisons:
> > https://files.lynne.ee/bwdif_01_before.png
> > https://files.lynne.ee/bwdif_01_after.png
> > Generated from sample 1 via:
> > ffmpeg -ss 00:00:00.184 -i <INPUT>.nut -vf
> crop=w=420:h=240:x=700:y=300,scale=iw*2:ih*2 -y <OUTPUT>.png
> >
> > https://files.lynne.ee/bwdif_02_before.png
> > https://files.lynne.ee/bwdif_02_after.pngffmpeg -ss 00:00:00.417 -i
> <INPUT>.nut -vf crop=w=420:h=240:x=1100:y=200,scale=iw*2:ih*2 -y
> <OUTPUT>.png
> >
>
> Corrected links for the second sample:
>
> https://files.lynne.ee/bwdif_02_before.png
> https://files.lynne.ee/bwdif_02_after.png
> ffmpeg -ss 00:00:00.417 -i <INPUT>.nut -vf
> crop=w=420:h=240:x=1100:y=200,scale=iw*2:ih*2 -y <OUTPUT>.png
>
> I'm sure I hit a newline. The artifacts are a lot more noticeable in the
> second sample.
>

Single png images are not way to prove something.

Please provide videos and not just single file that exhibit this issue.
(Keep showing same file over and over is not going to help show that it
helps)

Also how PSNR/SSIM/VMAF changes before after not just in single sample but
in more samples.



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