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

[edit 'B]

> On 17 May 2025, at 16:44, Alex Xu <alexkurosakimh3 at gmail.com> wrote:
> 
> The video is telecined, not interlaced.

Telecined IS ALWAYS interlaced. The whole idea is to create something to reduce doubling frames as much as possible.
Having said this, de-interlacing is NOT reverse telecine, and should not be used to show telecine on progressive displays.

Bouke 

> 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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