[FFmpeg-user] Source v210.mov has no interlacement info, ffv1 transcode is listed as progressive

[Jerome Martinez]

Le 28/07/2016 à 10:38, Kieran O Leary a écrit :
> Hi,
>
> My  input file was generated from Avid Media Composer 8.
> Link: https://www.dropbox.com/s/yed44wj5lq9jg8h/2fr.mov?dl=0
>
> If I use -c copy to remux to mov or mkv, then the lack of
> interlacement info is maintained. When I encode with FFV1, using
> either MKV or MOV, the file is listed as progressive in mediainfo.
>
> However, the issue may not be specific to FFV1 as progressive values
> appear in mediainfo when using -c:v prores (in mov container) and
> libx264 in mov and mkv.

The difficulty here is to define "progressive": is it how it is coded or 
how it should be displayed?
your input is coded progressively (one v210 frame) despite the fact (you 
affirm it) your ingest is TFF (there is no info about it in the input file).
I guess that FFmpeg considers by default that v210 is always to be 
displayed progressive and sets the FFV1 encoder to progressive (value 3) 
instead of "unknown" (value 0) in the FFV1 bitstream.

You can force FFmpeg to configure the encoder with interlacement.
ffmpeg -i 2fr.mov -vf "interlace=lowpass=0:scan=tff"  -c:v ffv1 -level 3 
out.mkv
https://ffmpeg.org/ffmpeg-all.html#interlace

and your FFV1 stream is coded as interlaced (with an improvement about 
file size)
(note: the result is interlaced but looks like there is only 1 frame 
instead of 2, please double-check the command line; I am not a FFmpeg 
expert so a better command line would be appreciated)

But please use it only if you are sure about your input because other 
people will rely on this information.

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