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Rotation Metadata

Metadata iphone rotate rotation

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#1 cyberjaws



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Posted 02 December 2014 - 04:14 AM

I know that quicktime and vlc check for the rotation flag in the meta data to properly orient video.  Would it be possible to detect this flag and pass the rotate command to FFMPEG when transcoding/streaming to ensure that video is oriented correctly?  I noticed this when I attempted to steam some movies I had taken on my iPhone.  Thanks for your efforts, I have converted most of my friends and family to your product and we are all very happy customers!

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#2 admin



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Posted 02 December 2014 - 04:21 PM

This is actually quite tricky to do. I'm aware of the issue but the problem is that there are 3 different ways MP4 with rotate flags can be played and we can't support it in every way.


1. Direct Streaming - this should work (once we fix the renderer to account for the flag), however we disabled mp4 direct streaming by default because many mp4 files out there cause various issue for iOS mediaserverd (which decodes and plays the video).


2. MP4 playback with transcoding. We can do anything we want here, including rotation, but that would mean that H.264 stream inside mp4 file is transcoded when it doesn't have to, which is something we usually don't (it's much faster to preserve the original stream and the original quality is preserved)


3. MP4 playback with remuxing. This is what we do by default. We don't serve the file as MP4, bit we keep the original video stream so that no transcoding is necessary. This means that we don't encounter the problems with direct MP4 playback (i.e. buffering issues, etc), but it is also very fast and there is very little CPU usage. The downside is that there is no way to pass the rotation flag to player. We could rotate the rendering surface, but even then it would not work on Apple TV.


So this is something that needs to be addressed, but to do it properly it needs quite a bit of work.

#3 cyberjaws



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Posted 03 December 2014 - 03:37 AM

Thank you for the thorough response!  I figured if it was something low hanging you would have already incorporated the feature :).  Too bad they don't give you more flexibility on the client side to leverage the device's GPU to perform the translation.  Appreciate your efforts, thanks again!

#4 mick



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Posted 06 March 2015 - 10:22 PM

Another request for this feature. Seems like it's not trivial to address but it would make the app much more useful to those of us that store our iOS created movies remotely.


Cheers and thanks for the great work.

Also tagged with one or more of these keywords: Metadata, iphone, rotate, rotation

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