Cut and speed-up videos

ffmpeg_magic.sh

#!/bin/bash

# This script take a video as a command line argument
# dividing it in three parts, then speeds up the middle part,
# and finally joins the parts into a final `output.mp4` video.

# First section of the video to cut
T1="00:00:10"
T1HALF="00:00:05"
# Second section duration
T2="00:00:30"
# Third section that last until the end
# (it's T1 + T2)
T3="00:00:40"

# Speed (1 = 100%)
SPEED=0.3

if [[ $1 != "" ]];then
    ffmpeg -i $1 -t $T1 part-1.mp4
    ffmpeg -ss $T1HALF -i $1 -ss $T1HALF -t $T2  slow.mp4
    ffmpeg -i $1 -ss $T3 part-3.mp4

    ffmpeg -i slow.mp4 -filter:v "setpts=$SPEED*PTS" part-2.mp4

    for f in $PWD/part-*.mp4;
        do echo "file '$f'" >> myvideos.txt
    done
    ffmpeg -f concat -safe 0 -i myvideos.txt -c copy output.mp4

    # Removing temporary files
    rm -f part-*.mp4 slow.mp4 myvideos.txt
else
    echo "Usage:\n\tspeed_up_videos VIDEO"
fi