The following is to download a only a particular part of a video from YouTube
ffmpeg -i $(youtube-dl -f 22 --get-url https://www.youtube.com/watch?v=cmne_rokrs4) -ss 00:10:10 -to 00:12:52 -c:v copy -c:a copy happy.mp4
Or you can download all the video first and then cut some parts following the instructions here.
If you want to concatenate MP4 videos (you can prepare an script):
echo file input1.mp4 > mylist.txt
echo file input2.mp4 >> mylist.txt
ffmpeg -f concat -i mylist.txt -c copy output.mp4
To list all subs for a video:
youtube-dl --list-subs URL
To download all subs, but not the video:
youtube-dl --all-subs --skip-download URL
Or you can only download one subtitle
youtube-dl --write-sub --sub-lang en --skip-download URL
Or for downloading the automatically generated subtitles
youtube-dl --write-auto-sub --skip-download URL
If you want to convert the subtitles do:
ffmpeg -i input.vtt output.srt
The following is to convert videos to a higher speed. For instance, if you want to multiply by 1.15, the command is:
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.87*PTS[v];[0:a]atempo=1.15[a]" -map "[v]" -map "[a]" output.mkv
#The "setpts" corresponds to the inversed speed (in this case 100/1.25 = 0.8)
#while the "atempo" corresponds to the desired direct speed of the video.
#Those values are proportionally inversed.
#For a 25% higher speed output video the values
#would be "setpts=0.8*PTS" and "atempo=1.25"
100/1.25 = 0.8
