Here is another FFmpeg-related blog post, this time to explain how to rotate a video using the command-line tool FFmpeg. There are two ways of doing this, and I will explain both in the following.
Rotation in metadata
The best first try could be to make the rotation by only modifying the metadata in the file. This does not work for all file types, but should work for some (including .mp4) files.
ffmpeg -i input.mp4 -metadata:s:v rotate="-90" -codec copy output.mp4
The nice thing here is that it is superfast and also non-destructive.
Rotation with compression
If the above does not work, you will need to recompress the file. That is not ideal, but will do the trick. To rotate a movie by 90 degrees, you can do:
ffmpeg -i input.mp4 -vf "transpose=1" -c:a copy output.mp4
The trick here is to use the rotation value:
- 0 – Rotate by 90 degrees counter-clockwise and flip vertically. This is the default.
- 1 – Rotate by 90 degrees clockwise.
- 2 – Rotate by 90 degrees counter-clockwise.
- 3 – Rotate by 90 degrees clockwise and flip vertically.
I often record with cameras hanging upside down. Then I want to rotate 180 degrees, which can be done like this:
ffmpeg -i input.mp4 -vf "transpose=2,transpose=2" output.mp4
Even though the video is re-compressed using this method, you can force the audio to be copied without compression by adding the -c:a copy tag:
ffmpeg -i input.mp4 -vf "transpose=1" -c:a copy output.mp4
Of course, these commands can also be included in a chain of other FFmpeg-commands.