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

[Nicolas George]

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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