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I have a video in mp4 with frame rate of .33 (i frame for 3 seconds). I want to increase the frame rate to 5 frames/sec. I have tried the below command but it does not do any thing...

ffmpeg -i <input.mp4> -r 5 <output.mp4>

Any idea why ffmpeg is ignoring -r option.

thank you

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migrated from Aug 7 '11 at 8:40

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If you're trying to speed up / slow down a video, instead of duplicate / drop frames, see… and/or… – Peter Cordes Mar 1 at 2:50

2 Answers 2

If the input file doesn't have a valid frame rate you might have to set it explicitly

ffmpeg -r 1 -i input.mp4 -r 24 output.mp4
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I could only get the changed framerate to take effect if the input file was classed as a "raw" file:

ffmpeg -r 5 -f h264 -i input.h264 -vcodec copy -an output.mkv

Without specifying -f h264 it would default to 25 fps and it could not be changed. Apparently this was because the stream lacked any framerate information at all and this is ffmpeg's default framerate.

Apparently when you use -r as an output option it duplicates or drops frames so the video plays at the same speed - in this case, not what you want! But changing the input framerate as above will cause the video to speed up or slow down, with no frames lost or duplicated.

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