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

[Alex Xu]

Thanks for your feedback, I tried your command but added a frame counter:

ffmpeg -i detelecine_input.mkv -vf
"fieldmatch=order=tff:combmatch=none,decimate,drawtext=fontfile=Arial.ttf:
text='%{frame_num}': start_number=0: x=(w-tw)/2: y=h-(2*lh):
fontcolor=black: fontsize=20: box=1: boxcolor=white: boxborderw=5" -c:v
libx264 -crf 18 -c:a aac -b:a 192k -pix_fmt yuv420p -r 24
fieldmatch_decimate_frames.mkv

I also adjusted my original command to add a frame counter:

ffmpeg -i detelecine_input.mkv -c:v libx264 -crf 18 -c:a aac -b:a 192k
-pix_fmt yuv420p -vf
"detelecine=start_frame=3:pattern=2332,drawtext=fontfile=Arial.ttf:
text='%{frame_num}': start_number=0: x=(w-tw)/2: y=h-(2*lh):
fontcolor=black: fontsize=20: box=1: boxcolor=white: boxborderw=5"
 detelecine_2332.mkv;

In my original command, the final result has every video frame being
unique, but your command has some duplicated and dropped frames. The
overall video does look smooth though apart from that.
For example, using fieldmatch+decimate, frames 174+175 are duplicated. And
the original frame 173 is missing.

So maybe detelecine has a bug where I need to use wrong params to get the
correct result?

anyways, thanks for looking into it, maybe this is a filter bug? Ultimately
I did get the correct result (with the wrong params?)

Alex

On Thu, May 22, 2025 at 7:27 PM Huspnet <llee040 at sbcglobal.net> wrote:

>
>
> > On May 22, 2025, at 9:04 PM, Huspnet <llee040 at sbcglobal.net> wrote:
> >
> > Here's a detelecine alternative method that might be worth trying.
> >
> > ffmpeg -i detelecine_input.mkv -map 0:0 -vf
> fieldmatch=order=tff:combmatch=none,decimate,crop=640:480:0:0 -c:v
> h264_videotoolbox -b:v 2800k -color_primaries:v bt709 -color_trc:v bt709
> -colorspace:v bt709 -metadata:s:v "title=" -disposition:v default -map 0:1
> -c:a:0 copy -metadata:s:a:0 "title=" -disposition:a:0 default -metadata:g
> "title=" -r 24 -movflags disable_chpl detelecine_output.mkv
> >
> > L. Lee
>
> Oops, sorry about that Mac stuff. Here's a different example. The filter
> chain (maybe rate setting, too) is what matters, I hope. Detelecined the
> provided example anyway.
>
> ffmpeg -i detelecine_input.mkv -vf
> fieldmatch=order=tff:combmatch=none,decimate,crop=640:480:0:0 -c:v libx265
> -b:v 3000k -c:a:0 copy -r 24 detelecine_output.mkv
>
> L. Lee
>
>
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