[FFmpeg-user] Questions about w3fdif deinterlacing

Christian Ebert blacktrash at gmx.net
Sun Jan 19 23:08:35 CET 2014

* Andy Furniss on Sunday, January 19, 2014 at 20:35:39 +0000
> Christian Ebert wrote:
>> ffmpeg -y -v quiet -i prog-int.ts -an -vf yadif=1 test.mp4
>> ffprobe -show_frames test.mp4 2>/dev/null | grep -c video
>> 2356
>> ffmpeg -y -v quiet -i prog-int.ts -an -vf yadif=1:deint=interlaced test.mp4
>> ffprobe -show_frames test.mp4 2>/dev/null | grep -c video
>> 2356
>> ffmpeg -y -v quiet -i prog-int.ts -an -vf idet,yadif=1 test.mp4
>> ffprobe -show_frames test.mp4 2>/dev/null | grep -c video
>> 2348
>> ffmpeg -y -v quiet -i prog-int.ts -an -vf idet,yadif=1:deint=interlaced test.mp4
>> ffprobe -show_frames test.mp4 2>/dev/null | grep -c video
>> 2348
> It seems this is because you are muxing to mp4 - I assume, but don't
> know that it can't handle the different framerates that result from
> using yadif=1.

You are so right.

> The output of your commands without the -v quiet shows eg.
> frame= 2356 fps= 17 q=-1.0 Lsize=   66806kB time=00:00:47.08
> bitrate=11624.3kbits/s dup=432 drop=0
> So 432 frames have been duplicated these look to be the progressive ones.
> The difference in number between those flagged as progressive (408)
> are all the first frame duped, though slightly strange because of the
> -an the explanation is probably that the sound is 1 sec ahead of the
> video in the prog-int.ts stream.
> This does not happen if you change mp4 to mkv - the container will
> show 50fps, but the pts timestamps vary to give 25 fps then 50 fps.
> I don't know how compatible this is with players generally, but it
> works with mplayer.

Thank you for taking the time to explain.

>> And I don't understand why deinterlacing takes place in the
>> following case:
>> [Parsed_idet_0 @ 0x7f9c24000000] Single frame detection: TFF:0 BFF:0 Progressive:928 Undetermined:303
>> [Parsed_idet_0 @ 0x7f9c24000000] Multi frame detection: TFF:0 BFF:0 Progressive:1210 Undetermined:21
>> ffprobe -select_streams v -show_frames test.vob 2>/dev/null | grep -c video
>> 1232
>> ffmpeg -y -v quiet -i test.vob -vf idet,yadif=1 test.mp4
> This should be -vf idet,yadif=1:deint=interlaced for yadif to honor
> what idet detects.

Indeed converting to mkv shows the difference.

Thanks again.

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