FFmpeg speed up video

Speed up and smaller:
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

Speed up and bigger:
ffmpeg -i in.mp4 -vf "setpts=0.5*PTS" -r 50 -c:v mpeg4 -b:v 1500k -af "atempo=2" out.mp4



For .bat in folder on Windows:
for %%* in (.) do set DirName=%%~nx*
mkdir "%DirName%"
for %%i IN (*.mp4) DO ffmpeg -i "%%i" -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" "%DirName%/%%i"
pause



If you want to convert other-format video to .mp4 on Windows:
for %%a in ("*.flv") do ffmpeg -i "%%a" -codec copy "%%~na.mp4"
for %%a in ("*.flv") do del "%%a"

If you want to convert other-format to .mp4 on linux:
for file in *.mkv; do sudo ffmpeg -i "$file" -codec copy "${file%.mkv}".mp4; done
rm -fr *.mkv
(
sudo mkdir done
for file in *.mp4; do sudo ffmpeg -i "$file" "done/${file%.mp4}".mp3; done
)



Left channel to mono:
ffmpeg -i video.mp4 -map_channel 0.1.0 -c:v copy mono.mp4

If you want to use the right channel, write 0.1.1 instead of 0.1.0.