Skipping a frame without re-encoding H.264 video

Question

I have an mp4/h.264 video which only contains I-Frames. I want to skip one of those I-frame without re-encoding the entire video. I tried this:

ffmpeg -i "file.mp4" -vf select='not(eq(n\,10))' "out.mp4"

But of course this actually does a re-encoding.

I would prefer if the solution will use ffmpeg, but any program which runs on Linux is fine.

Just to be clear: the video does not contain any P or B frame.

Answer 1

If you want to remove a single I-frame, you have to extract the bitstream to an Annex B format (e.g. ffmpeg -i input.mp4 -c:v copy -an output.h264, and then find the bytes that represent the NAL unit(s) containing the frame(s) you want to remove. Remove those bytes until the next start code, and save the stream.

Or, you could splice the video by using the -frames:v option to extract the first n frames:

ffmpeg -i input.h264 -c:v copy -frames:v n output.h264

Then, using the -ss parameter, you could seek to the position where you want to start again, and cut from there the same way. You could find out the position by multiplying n+1 times the framerate.

There is no simpler way I know of if you do not want to re-encode.