To double the speed of audio:įfmpeg -i input.mkv -filter:a 'atempo=2.0' -vn output.mkv You can speed up or slow down audio with the atempo audio filter. Other options include slowmoVideo and Butterflow. This is also known as 'motion interpolation' or 'optical flow'.įfmpeg -i input.mkv -filter:v 'minterpolate='mi_mode=mci:mc_mode=aobmc:vsbmc=1:fps=120'' output.mkv You can smooth out slow/fast video with the minterpolate video filter. To slow down your video, you have to use a multiplier greater than 1:įfmpeg -i input.mkv -filter:v 'setpts=2.0*PTS' output.mkv For example, to go from an input of 4 FPS to one that is sped up to 4x that (16 FPS):įfmpeg -i input.mkv -r 16 -filter:v 'setpts=0.25*PTS' output.mkv You can avoid dropped frames by specifying a higher output frame rate than the input. Note that this method will drop frames to achieve the desired speed. For example, if there are two succesive frames shown at timestamps 1 and 2, and you want to speed up the video, those timestamps need to become 0.5 and 1, respectively. The filter works by changing the presentation timestamp (PTS) of each video frame. To double the speed of the video with the setpts filter, you can use:įfmpeg -i input.mkv -filter:v 'setpts=0.5*PTS' output.mkv Then generate new timestamps while muxing to a container:įfmpeg -fflags +genpts -r 30 -i raw.h264 -c:v copy output.mp4Ĭhange the value of -r to the desired playback frame rate. Use this if you require no other changes to your input video.įirst, copy the video to a raw bitstream format.įfmpeg -i input.mp4 -map 0:v -c:v copy -bsf:v h264_mp4toannexb raw.h264įfmpeg -i input.mp4 -map 0:v -c:v copy -bsf:v hevc_mp4toannexb raw.h265 This method is lossless and apart from changing the timestamps, copies the video stream as-is. Note that in the following examples, the audio stream is not changed, so it should ideally be disabled with -an. This can be done via two methods: using the setpts video filter (which requires re-encoding) or by erasing the timestamps by exporting the video to a raw bitstream format and muxing to a container while creating new timestamps.

The speed of a video stream can be changed by changing the presentation timestamp (PTS) of each video frame.

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