opencv - video looks good but frames are rotated 90 degrees

Question

We save a video on a mobile client and send it to a server. On the server, I use the following code to save the frames:>

import skvideo.io
import cv2

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Answer 1

there was a glitch in skvideo, it was not reading the available metadata. For videos taken in mobile are rotated, but metadata includes such parameter. The skvideo team committed a fix, and current skvideo version 1.1.7 reads metadata from mobile, that indicates that video should be rorated. skvideo.io.vread then rotates the file:

1) use newer skvideo version, 1.1.7 which can be cloned at https://github.com/scikit-video/scikit-video

2) You can use following code to read all frames in the video, most likely metadata will be read

import skvideo.io
videogen = skvideo.io.vread(f.name)

That will rotate the video automatically if it was taken in portrait mode.

3) Created an issue on skvideo repo, take a look for further reference: https://github.com/scikit-video/scikit-video/issues/40

Answer 2

It looks like OpenCV does not record the rotation metadata of the video file with VideoCapture() as you can see by the propIds that it stores.

I'm not sure if scikit-video does. It looks like they have a metadata puller called ffprobe which might be able to pull the rotation. See here for an example of how to call and see the output. This shows a hefty list of metadata---no rotation---but that might just be because it's not set or of a movie type which doesn't have rotation metadata.

Another way to grab it would be to read the metadata directly from ffmpeg. I found an old StackOverflow answer that wrote a little python code to extract specifically the rotation metadata from a video using ffmpeg.