[FFmpeg-user] Confusion about fieldmatch, decimate and framerate (now with yadif)
nickrobbins at yahoo.com
Sun Nov 10 17:20:59 CET 2013
On Sat, 11/9/13, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
Subject: Re: [FFmpeg-user] Confusion about fieldmatch, decimate and framerate (now with yadif)
To: ffmpeg-user at ffmpeg.org
Date: Saturday, November 9, 2013, 11:52 PM
>Nicholas Robbins <nickrobbins <at> yahoo.com> writes:
> > Ok, on my current sample. I checked the length and
> > framecount using ffmpeg, getting: Frames: 169698
> > Duration: 1:34:19.29 for a frame rate of 29.97.
> I apparently miscalculated, sorry.
No problem. Good to know that this is the right way to determine framerate.
> > In the encode, I get this quite a bit:
> > "Frame #328307 at 10954.5 is still interlaced" So I think,
> > I should add> in yadif=deint=interlaced as per
> > http://ffmpeg.org/ffmpeg-filters.html#Examples-37 between
> > the fieldmatch and the decimate.
> Sounds correct and reasonable to me.
> Did you extract the offending frame as fieldmatch outputs
> it and compared it with the same frame as output by
> fieldmatch,yadif=deint=interlaced ?
> Every other test is meaningless.
I have done so now. They appear almost identical (as far as I can tell using gimp). The commands I used were:
ffmpeg -i start.mkv -map 0 -c copy -c:v libx264 -vf "fps=30000/1001,fieldmatch,yadif=deint=interlace" -crf 17 -preset veryfast fieldmatch-yadif.mkv
ffmpeg -i start.mkv -map 0 -c copy -c:v libx264 -vf "fps=30000/1001,fieldmatch" -crf 17 -preset veryfast fieldmatch.mkv
both of which produced:
Frame #8158 at 272.239 is still interlaced time=00:04:32.25 bitrate=2560.3kbits/s
[Parsed_fieldmatch_1 @ 0x6c7357b3e0] Frame #8159 at 272.272 is still interlaced
[Parsed_fieldmatch_1 @ 0x6c7357b3e0] Frame #8160 at 272.305 is still interlaced
among many other similar lines in their output. I picked this run because it was the longest. Most were 2 frames.
Then I used
ffmpeg -i fieldmatch-yadif.mkv -frames 8170 /var/srv/media/videos/Testing/Postal/jpegs/fieldmatch-yadif-%d.bmp (and without the -yadif)
To get the relevant frames.
> ( This tests something else which is 100% unrelated
> (and which you should really ignore / forget if
> you are interested in inverse telecine, there is
> no real world stream that sets this the way you
> test it.)
Ok, I'll ignore that flag.
> > I guess fieldmatch doesn't mark the frames it can't
> > deal with. It just leaves them where they are.
> This would be a serious bug, if you can actually reproduce
> it, please upload the five-ten relevant frames.
Done. I've put them in robbins-fieldmatch-yadif.tgz in incoming.
> Carl Eugen
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