[FFmpeg-user] Detelecine: I got the right result from the wrong command?

[Alex Xu]

The video is telecined, not interlaced.

On Fri, May 16, 2025 at 11:39 PM Richard Bartczak via ffmpeg-user <
ffmpeg-user at ffmpeg.org> wrote:

> Am 17.05.25 um 06:03 schrieb Alex Xu:
> > Hi everyone,
> >
> > I'm working to detelecine a video, attached here (12 MB, first 32 seconds
> > truncated):
> > https://www.mediafire.com/file/x4ly6moqb8ayfyy/detelecine_input.mkv/file
> >
> > I wasn't sure what was the right command to get the result I wanted so I
> > looped over all possible combos like so:
> >
> > for i in 0 1 2 3 4; do
> > for j in 23 2332; do
> > ffmpeg -i detelecine_input.mkv -c:v libx264 -crf 18 -c:a aac -b:a 192k
> > -pix_fmt yuv420p -vf "detelecine=start_frame=$i:pattern=$j"  $i$j.mkv;
> > done
> > done
> >
> > It was very clear which option was correct, since the correct option
> > encoded the best and had a significantly smaller file size. I visually
> > verified it too. In the source, every set of 5 frames had 3 clear frames
> > and 2 interleaved frames. In the final output, it preserved those 3 clear
> > frames and combines the 2 interleaved frames into 1, going from 30i to
> 24p.
> >
> > But I'm just not sure why the correct result was
> start_frame=3:pattern=2332.
> >
> > Examining the video, it seems pretty clear to me the pattern should be
> 23.
> > Since it has two interleaved frames. I learned about 23 from
> > https://en.wikipedia.org/wiki/Telecine#2:3_pulldown
> >
> > Could someone explain the gap in my knowledge?
> >
> > Alex
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>
> If you want to get the progressive mode :
>
> ffmpeg -i "interlacevideo.mkv" -vcodec libx264 -crf 18 -preset slow -vf
> yadif -c:a copy "progressivevideo.mkv"
>
> Richard
>
>
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