[FFmpeg-user] Pullup filter is introducing chroma lag

[Paul B Mahol]

On 3/8/22, llee040 <llee040 at sbcglobal.net> wrote:
>
>
>> On Mar 8, 2022, at 11:32 AM, morgan holly via ffmpeg-user
>> <ffmpeg-user at ffmpeg.org> wrote:
>>
>> Hi,
>>
>> I’m trying to remove telecine from a prores mov file using the pullup
>> filter:
>>
>> Source file:
>> Video: prores (LT), top coded first (swapped)), 720x480, 29.97 fps, 29.97
>> tbr, 30k tbn, 30k tbc (default)
>>
>> Command:
>> ffmpeg -i pullup_test.mov -an -vf pullup -r 24000/1001 -pix_fmt yuv420p -y
>> pullup_test1.mov
>>
>> Result:
>> Every fourth frame on the 23.976 output has chroma lag (3/2 removed from
>> luma, but chroma is still interlaced). Dejudder doesn’t fix it and
>> fieldmatch+decimate does worse things.
>>
>> Test sources:
>> I’ve seen the artifact on both live action and clean animation sources. I
>> cannot share the sources but created a short example that can be used to
>> recreate the issue:
>>
>> Test source with 3/2:
>> http://videopress.s3.amazonaws.com/misc/pullup_test.mov
>> <http://videopress.s3.amazonaws.com/misc/pullup_test.mov>
>>
>> Test pullup 23.976 output:
>> http://videopress.s3.amazonaws.com/misc/pullup_test_1.mov
>> <http://videopress.s3.amazonaws.com/misc/pullup_test_1.mov>
>>
>> Thanks for any help!
>>
>
> Not sure if this will help but it seemed to create slightly better output
> for your test movie when substituted for “pullup”:
>
> detelecine=first_field=b:start_frame=0,yadif=deint=interlaced

If it still use yuv420p as first format in chain, it is wrong and not
correct approach.

>
> ffmpeg -i pullup_test.mov -an -vf
> detelecine=first_field=b:start_frame=0,yadif=deint=interlaced -r 24000/1001
> -pix_fmt yuv420p -y pullup_test1.mov
>
> L. Lee
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