[FFmpeg-user] Framerate Question

Andrey Utkin andrey.krieger.utkin at gmail.com
Mon Mar 5 11:47:01 CET 2012

2012/3/5 Jared McIntyre <jmcintyre at dfsoftware.com>:
> I'm re-encodeing broadcast video. The source was apparently 720 30fps, but is being broadcast 60fps where every frame appears twice. I thought I'd try to save some space by re-encoding and using 30fps to cut out every other frame. I used the following command:

I believe x264 encoder is able to compress efficiently in this case,
without such a hack.

> ffmpeg -i in.mpg -acodec libfaac -ab 160k -crf 23.1 -vcodec libx264 -tune animation -preset faster -profile baseline -f mp4 -r 29.97 out.mp4
> I was a bit surprised to find out that if I used -r 29.97 I would get a file with half the frames, but a larger size than if I hadn't done so. I'm sure I'm misunderstanding something, but is this the expected behavior? Here is the log data in case about the encodeing:

What's the intention of -tune animation flag?
To get video of desired bitrate, give that bitrate as a parameter.

I'd suggest to not change framerate, and just tune encoder options to
have satisfying output size or quality.
Start from simply transcoding it without any options, just setting
desired bitrate.

Andrey Utkin

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