FFMPEG Command to Cut or Trim Videos By Exact Frames of Video Timestamp on Command Line



timecode_frame_start does not work like this.

Seeking based on frame numbers is not possible. The only way to start at specific frames is to convert a number of frames to ss.ms syntax, or hh:mm:ss.ms. So, if your video is at 25 fps, and you want to start at 133 frames, you would need to first calculate the timestamp:

133 / 25 = 5.32

Then run:

Note that cutting on exact frames with bitstream copy (-c:v copy) is not possible, since not all frames are intra-coded (“keyframes”). A video must begin with a keyframe to be decoded properly. You will therefore have to re-encode the video, e.g. to H.264 using -c:v libx264 as shown above. You can also choose a lossless codec like -c:v ffv1 which preserves the quality of the input video.

To summarize, -ss will always be frame-accurate when performing re-encoding.

If you further want to encode a specific number of frames, use -frames:v, for example:

Note that you you also have the choice to use the select/aselect filters to select frames/audio samples.

This, however, is slower than the -ss option shown above, since the entire video will be decoded.


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