ffmpeg converts double length on MacOS

ffmpeg creates double length of mp3 from mp4 on MacOS ======================================================= Symptom -------- When you try to extract a sound file from a video file on MacOS, ```bash $ ffmpeg -i video.mp4 sound.mp3 ``` you'll get a sound file but it has double the length of the video, e.g. 10' in a video to 20' in a sound. Solution -------- You'd better put an option (`-write_xing 0`) to evade automatic treatment on a command line ```bash $ ffmpeg -i video.mp4 -write_xing 0 sound.mp3 ```

How to rotate a video file?

You may have done this

$ ffmpeg -vfilter "rotate=90" -i input.mp4 output.mp4

but you would have

unrecognized option 'vfilters'.

Error splitting the argument list: Option not found

So you should run:

$ ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

then input.mp4 will be rotated at 90 degrees to output.mp4.