You can use mkvtoolnix, then go to -> output, and -> splitting -> by parts based on timestamps -> and there you can write the beginning and the end of the part you want extract (without spaces: like 1:02:07-1:04:40, for example).
linux. how to get images from a (short) video
You can use this code:
ffmpeg -i [nameofthevideo] -r 10 -f image2 image-%3d.jpeg
where 10 after -r is the number of images per second. So you can change it, according to your needs.
avidemux too slow
It’s better use (one of) the following codecs for encoding
-
x264
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libavcodec MPEG-1/MPEG-2
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libavcodec MPEG-4
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Xvid
so Avidemux will be able to optizmize the CPU usage and will be much faster. And the CPU temperature will be lower.
Cfr.here.