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

[Lynne]

Jul 2, 2023, 20:41 by tmundt75 at gmail.com:

> Am So., 2. Juli 2023 um 18:57 Uhr schrieb Lynne <dev at lynne.ee>:
>
>> 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.
>>
>
> I developed the bwdif to achieve the best possible balance between speed
> and quality of all different image contents from the broadcast point of
> view. This includes moving video as well as moving and static graphic
> elements. Unfortunately, the improvement of one image content often leads
> to the degradation of another. The code you removed fundamentally
> stabilizes the static graphic elements. This outweighs the slightly more
> frequent artifacts in moving video considering the general purpose of the
> filter.
>

Could you post examples? I've been unable to find any that look worse
with the patch.