How to split a video using FFMPEG so that each chunk starts with a key frame?

Question

We need to split a large live WMV video feed in small chunks all of the same size. We made a script that works fine doing this, except for one thing: the video chunks don't start with a key frame, so when playing most video chunks they don't display any image until a key frame from the original video is eventually reached.

Isn't there a way to tell ffmpeg to make the output video to start with a key frame?

Here is how our command lines look right now:

ffmpeg.exe -i "C:\test.wmv" -ss 00:00:00 -t 00:00:05 -acodec copy -vcodec copy -async 1 -y  "0000.wmv"
ffmpeg.exe -i "C:\test.wmv" -ss 00:00:05 -t 00:00:05 -acodec copy -vcodec copy -async 1 -y  "0001.wmv"

and so on...

Answer 1

The latest builds of FFMPEG include a new option "segment" which does exactly what I think you need.

ffmpeg -i INPUT.mp4 -acodec copy -f segment -vcodec copy -reset_timestamps 1 -map 0 OUTPUT%d.mp4

This produces a series of numbered output files which are split into segments based on Key Frames. In my own testing, it's worked well, although I haven't used it on anything longer than a few minutes and only in MP4 format.