[FFmpeg-devel] [PATCH v2 2/2] fftools/ffmpeg: Add stream metadata from first frame's metadata

[Jun Li]

On Thu, May 9, 2019 at 1:52 AM Nicolas George <george at nsup.org> wrote:

> Jun Li (12019-05-06):
> > I agree with it that the patch can't solve the case that "not all frames
> > have the same orientation".
> > The only way I can think of (correct me if I am wrong) is a filter that
> > dynamic do tranformation per frame.
> >
> > From a technical perspective, this kind of media is absolutely possible.
> > For example motion jpeg consists of jpg with different orientations.
> > But I assume it is rare with my limited knowledge. What do you think?
>
> I think they can be quite common: imagine somebody trying to make a
> slideshow from vacation photos.
>
> A filter that applies the transform on each frame based on the metadata
> would be my first idea too. We already have the filter: the one that
> does the transform right now. It needs to be adapter to change the
> transform on a per-frame basis. That should be easy.
>
> But it is a bit harder than that: lavfi does not support real
> reconfiguration of the stream properties. Therefore, this filter must be
> added to the small list of "temporary" exceptions in the framework. And
> the user will need to insert scale/pad/crop to normalize the output.
> That needs to be documented.
>
> Regards,
>
> --
>   Nicolas George
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Hi Nicolas,
Thanks for the input, I will take a look at the transform filter.

The image's exif ("orientation") info is kept inside of frame metadata,
maybe the filter can
directly read from frame, instead of re-config the stream level metadata ?
How about that ?

Best Regards,
Jun