Getting metadata from video stream

[Sebastian Dröge]

On Mi, 2013-11-06 at 13:59 +0200, Mohammed Sameer wrote:
> On Mon, Nov 04, 2013 at 09:50:50AM +0100, Sebastian Dröge wrote:
> > On Sa, 2013-11-02 at 15:20 +0200, Mohammed Sameer wrote:
> > > On Tue, Oct 29, 2013 at 08:41:05AM +0000, Sebastian Dröge wrote:
> > > > On Mo, 2013-10-28 at 03:51 -0700, Blazej wrote:
> > > > > Hello,
> > > > > 
> > > > > Thanks for suggestion!:) I cannot see this parameter in the output of
> > > > > gst-discoverer, but maybe it's because I am limited to 0.10 version of
> > > > > gstreamer. 
> > > > > 
> > > > > Also, I did some research and found out that this kind of information is
> > > > > stored in 'Atoms', which are part of MPEG-4 standard. In such case maybe it
> > > > > is not supposed to be displayed by gst-discoverer, since it seems to display
> > > > > only the generic information about a file. But on the other hand, if ffprobe
> > > > > can detect this...
> > > > > Maybe these parameters should be accesible via qtdemux somehow?
> > > > 
> > > > I think extracting that information is currently not supported and
> > > > support for that has to be added to qtdemux. It should use the
> > > > image-orientation tag probably.
> > > 
> > > I think this is the rotation extracted from tkhd Atom transformation matrix.
> > > 
> > > There is a bug https://bugzilla.gnome.org/show_bug.cgi?id=679522 about that
> > > with a patch that extracts the info but it doesn't yet export it.
> > > 
> > > I'm personally interested in that issue but I'm not sure how should the data
> > > be exported.
> > 
> > See my comment in that bug :) For simple things we can export it via the
> > image-orientation tag, but additionally the complete matrix should
> > probably be exported as a GstMeta for the general case.
> 
> Thank you Sebastian for the reply.
> 
> I suggest we move the discussion to bugzilla then ;-)
> 
> image-orientation tag could be used indeed but we also need the GstMeta bits so sinks
> like xvimagesink can rotate the video automatically.

Yeah, or videoflip could handle it (which it already does in git
master). Needs some magic integration in playbin probably :)

> The matrix also have width and height "adjustments". I am not sure how the GstMeta API bits
> should look like. I can try to implement but we need an API draft I guess?
> 
> I think we also need a way to hand over such a matrix to mp4mux while we are encoding.

I think having the implementation of that GstMeta as an API proposal
would be best. Ideally with additionally patches to use it in several
plugins, so one gets a better idea if it's suitable.

But you're right, let's better handle that in the bug report :)

-- 
Sebastian Dröge <sebastian at centricular.com>
Centricular Ltd - http://www.centricular.com
Expertise, Straight from the Source
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