FFmpeg

1. brew tap varenc/ffmpeg
2. brew install varenc/ffmpeg/ffmpeg –with-fdk-aac

ffmpeg -i input.mp4 -ss 00:02:39 -to 00:03:05 -c:v copy -c:a copy output.mp4

for i in 0 30 60 90 120 150 180 210 240 270 300;ffmpeg -i dragon4.mix\ -\ Amateur\ Teikyou\ CD-ROM\ \(Japan\)\ \(NEC\ PC-FXGA\)-pBJu9J-Jw98.mp4 -ss $i -t 30 dragon_$i.mp4

ffmpeg -i video.mp4 -i audio.m4a -c copy output.mp4

ffmpeg -i “concat:input1.mp4|input2.mp4|input3.mp4|input4.mp4” -c copy output.mp4

ffmpeg -i $i -codec copy -map 0 ${i/.mkv}.mp4

1. Check which tracks are present and which IDs they have.
   ffprobe -v error -show_entries stream=index,codec_name,codec_type input.mkv
2. For the main conversion command, note that the first audio track in the source file is 0:a:0, the second is 0:a:1, etc. Here is an example for a batch one-line:
   exportdir=/yoko/share/export; for i in *.mp4;ffmpeg -i $i -map 0:a:0 -c copy $exportdir/${i/mp4}deutsch.m4a -map 0:a:1 -c copy $exportdir/${i/mp4}english.m4a

ffmpeg -v trace -i file.mp4 2>&1 | grep -e type:'mdat' -e type:'moov'

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5576c36880] type:'moov' parent:'root' sz: 9919011 40 1603822784
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5576c36880] type:'mdat' parent:'root' sz: 1593903733 9919059 1603822784

ffmpeg -i original.mp4 -movflags faststart -c copy new.mp4

ffmpeg -itsoffset 23.5 -i input.srt -c copy output.srt

for i in *.srt;do ffmpeg -itsoffset 23.5 -i $i -c copy ${i/srt/shifted.srt};done

lsmedia () {
        ls -1rt $@ | while read -r line
        do
                echo \"$line\"
                mediainfo --Inform="Video;%CodecID%" $line
                mediainfo --Inform="Audio;%CodecID%" $line
        done | sed 'N;N;s/\n/\; /g' | column -t -s ";"
}