Rotating Videos from iPhone on Linux

iPhone is nice to take videos. However, one headache is the video may be rotated by 90 degree if you play it with non-Apple software such as MPlayer on Linux or Windows. This tutorial will introduce how to rotate the video taken from iPhone or other sources on Linux by 90 degree.

The tool we choose to use is ffmpeg which can rotate video with video filters.

ffmpeg supports several “transpositions”:

0 = 90CounterCLockwise and Vertical Flip (default)
1 = 90Clockwise
2 = 90CounterClockwise
3 = 90Clockwise and Vertical Flip

To rotate 90 clockwise, we will choose “1” like:

ffmpeg -i in.mov -vf "transpose=1" -strict -2 out.mov

However, this can work but still has problems: 1) the video aspects are wrong. 2) the quality is relatively low.

To solve the problems, we can do it by one single shot: setting the aspect during rotating the video by specifying -s to ffmpeg. Now, the problem is how to get the video aspect. MPlayer can help here.

mplayer -frames 0 -identify ./in.mov 2>/dev/null | grep ^VIDEO

It will print out the aspect of the video like:

VIDEO:  [H264]  1920x1080  24bpp  29.970 fps  21551.4 kbps (2630.8 kbyte/s)

After it is rotated, it should be “1080×1920”. It may be quite large and usually can be reduced to some smaller one like “540×960” respectively if you like.

The ffmpeg command will be like:

ffmpeg -i in.mov -vf "transpose=1" -s 540x960 -strict -2 out.mov

Bonus: MPlayer can also rotate the video during playing:

mplayer -vf-add rotate=1 in.mov

It has the same problem as ffmpeg: it does not know the new aspect and you will need to set it manually. Making the video fullscreen and then turn it back will usually set the correct video aspect.

Eric Zhiqiang Ma

Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.

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