I'm trying to cut a video (a debate on TV) with FFmpeg without re-encoding, and I need to cut between 2 sentences a guy pronounce. I think the precise moment is between two keyframes, because whatever the timestamp I try to cut at, I always get too much sound (and video) or too few. Here is my ffmpeg command line :

ffmpeg -i video.mp4 -ss 0:0:0.9 -vcodec copy -acodec copy videoB.mp4 -y

I'm aware that the position of the -ss option in the command line matters: here, it is supposed to give me all the accuracy FFmpeg can offer. I know I'm probably trying to cut my video neither on a I-frame, nor on P- or B-frames.

So is there a way to get the closest (P- or B-) frame, doing some calculations with the preceding I-frame to generate a new I-frame, then start the video with this brand new I-frame and no sound, until the correct timestamp is reached. Then the video could go on normally.

I really don't want to bother me with re-encoding (which is an use of FFmpeg I don't master on command line). I'm using FFmpeg version 2.5.8-0ubuntu0.15.04.1.


  • You only wish to re-encode the split GOPs - that's called smart rendering. AFAIK, that's tricky to do manually with ffmpeg. Try SolveigMM Video Splitter - videohelp.com/software/SolveigMM-Video-Splitter
    – Gyan
    Nov 1, 2015 at 13:06
  • 1
    Thanks but I'm under Linux. Any other tool which would be more suitable to my environment ?
    – natsirt
    Nov 1, 2015 at 17:08
  • 2
    Also SolveigMM video splitter seems to not be free anymore ;D Nov 2, 2015 at 13:59
  • "without re-encoding". Not going to happen on any keyframe based file type, with any tool. Only possible on non-keyframe based files. Just re-encode with high fidelity. If you do this a lot, reconsider your workflow to include non-keyframe based files, or port directly from your source files to your end-user file with a single encode (difficult to create a workflow like that, but well worth it if you can).
    – user3643
    Jun 20, 2019 at 18:56

2 Answers 2


You can't do it simply, but here's a pretty good work around.

First, cut near the desired position (at keyframes) with stream copy and then re-encode the frame-exact part of the video. Let's say:

ffmpeg -ss 120 -t 40 -i input.mp4 -c copy -y temp.mp4
ffmpeg -i temp.mp4 -vcodec h264 -crf 21 -acodec mp3 -ss 1.080 -t 38.480 -y final.mp4

Thus, temp.mp4 starts before 120 sec and has a duration of at least 40 seconds and final.mp4 has a duration of exactly 38.48 seconds.

When processing my home videos and stuff recorded from television, I use (-2s) for the desired start position and (+4s) for the duration. During re-encoding, I use milliseconds.



There is no way to precisely cut a video with FFmpeg if you need to cut outside an I-frame without re-encoding.

You could try software that can handle "smart rendering", but I am not aware of any such software for Linux. On Windows, you could use "TMPGEnc MPEG Smart Renderer" or SolveigMM Video Splitter. The latter has serious performance issues. I highly recommend TMPGEnc, but it is not free.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.