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

[Lynne <dev@lynne.ee>]

Jul 2, 2023, 21:38 by onemda@gmail.com:

> On Sun, Jul 2, 2023 at 9:13 PM Lynne <dev@lynne.ee> wrote:
>
>> Jul 2, 2023, 20:48 by onemda@gmail.com:
>>
>> > On Sun, Jul 2, 2023 at 6:57 PM Lynne <dev@lynne.ee> wrote:
>> >
>> >> Jul 2, 2023, 18:54 by dev@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.
>> >
>>
>> I posted samples and instructions. Enough for a discussion.
>> I'm not posting gigabytes of uncompressed samples.
>> PSNR is irrelevant if there are visible artifacts.
>>
>
> Nope, you havent.
>
> Some strange samples.
> PSNR is relevant as also SSIM and VMAF.
>

Fair enough, on a 4k60 game recording, with lots of text and movement,
ffmpeg -i game_4k60test.mkv -filter_complex "[0:0] split [t1] [t2] ; [t2] interlace [t2] ; [t2] bwdif=mode=send_field [t2] ; [t1] [t2] ssim [t3]" -map "[t3]" -f null -

Before:
0.990397 (20.175775)
After:
0.990417 (20.184970)
Slightly higher, but not really significant.

PSNR (average):
32.711758
vs
32.704465
Slightly lower, but not really significant.


> Ignoring this does not help project, but just force tyrannic behavior.
>

Relax, I'm not going to make you write a stablediffusion filter source :)
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