FFmpeg

resize

$ ffmpeg -i input.mp4 -c:v libx265 -vtag hvc1 -vf scale=1920:1080 -crf 20 -c:a copy output.mp4

cut video

$ ffmpeg -ss 00:01:00 -to 00:02:00 -i input.mp4 -c copy output.mp4

merge video and audio

$ ffmpeg -i video.mp4 -i audio.wav -c copy output.mkv

concat multi videos

$ -af silenceremove=start_periods=1:start_duration=0:start_threshold=-50dB:detection=peak,areverse,silenceremove=start_periods=1:start_duration=0:start_threshold=-50dB:detection=peak,areverse

concat audio

code:bash

# convertion to pcm

for f in *.m4a

do

ffmpeg -i ${f%.*}.m4a -c:a pcm_s16le -ac 2 -ar 48000 -f s16le ${f%.*}.pcm

done

# concatenate files

cat blank.pcm part1.pcm blank.pcm part2c.pcm part2f.pcm blank.pcm part3.pcm blank.pcm part4.pcm blank.pcm > final.pcm

# back to .m4a

ffmpeg -f s16le -ac 2 -ar 48000 -i final.pcm -c:a aac -b:a 192K -ac 2 final.m4a