Just use what is built into ffmpeg to do exactly this.
ffmpeg -i invid.mp4 -threads 3 \
-vcodec copy -f segment -segment_time 10:00 \
-reset_timestamps 1 \
cam_out_h264_%02d.mp4
This will split it into roughly 10-minute chunks, split at the
relevant keyframes, and will output to the files cam_out_h264_01.mp4, cam_out_h264_02.mp4,
etc.