[FFmpeg-user] Specific interlacing issue

[Paul B Mahol]

On Mon, Apr 11, 2022 at 2:40 PM Ivo Noorlander via ffmpeg-user <
ffmpeg-user at ffmpeg.org> wrote:

> Hi there
>
> I run into an issue with the interlaced output of concatenated sources.


Very creative usage of telecine filter, I must admit.


>
>
> ffmpeg -i colours.mov -vf
> telecine=pattern=223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322223222232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323,setfield=tff
> "-r" "30000/1001" "-pix_fmt" "yuv422p10le" "-c:v" "prores_ks" "-profile:v"
> "3" "-vendor" "apl0" "-fla
>  gs" "+ilme+ildct" -top 1 -an colours_pulldown.mov
>
> This command creates a 29.97i version of a 25p source with pulldown that
> keeps the same length in 29.97. When a cut lands on the split frame, the
> top field is the shot before the cut and the bottom field the shot after
> the cut as checked by
> ffmpeg -ss 0.3003 -i colours_pulldown.mov -frames 1 -vf field=top
> top.png;ffmpeg -ss 0.3003 -i colours_pulldown.mov -frames 1 -vf
> field=bottom bottom.png
>
> However when another source processed before the pulldown, the resulting
> output has interleaved fields. The cuts that are on the split frame now
> have lines from one another which shows as colour casts, as can be seen
> when extracting the top.png and bottom.png.
>
> The command for concatenating the sources was
>
> ffmpeg -f lavfi -i smptebars=s=1920x1080:r=60000/1001:d=5 -i colours.mov
> -filter_complex
> "[0]interlace[int];[int]setfield=tff[v1];[1]telecine=pattern=223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322223222232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323223232232322323[telecin
>  e];[telecine]setfield=tff[v2];[v1][v2]concat=n=2:v=1:a=0[v]" -map "[v]"
> -pix_fmt yuv422p10le -r 30000/1001 -c:v prores_ks -profile:v 3 -vendor apl0
> -flags +ilme+ildct -top 1 -an -y colours_pulldown.mov
>
> Adding the -field_order tt command does not change this.
>
> Is this a prores_ks issue or am I not understanding interlacing correcty?
>

Interlacing removes half of information. I really dunno what is your end
goal.

Have you checked with lossless video encoders too?

-r 30000/1001 will insert somewhere fps filter, so you are on your own then.

Also make sure that at concat point everything is as intended.



> Hope you can help
>
> Thanks
> Ivo
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