[FFmpeg-devel] [PATCH]Reset rotation information when using the transpose filter

Reimar Döffinger Reimar.Doeffinger at gmx.de
Thu Nov 15 19:52:34 CET 2012

On Thu, Nov 15, 2012 at 11:31:07AM +0100, Clément Bœsch wrote:
> On Thu, Nov 15, 2012 at 10:07:14AM +0000, Carl Eugen Hoyos wrote:
> > Clément Bœsch <ubitux <at> gmail.com> writes:
> > 
> > >  - the user has a player honoring correctly the metadata, but he wants to
> > >    rotate the video even more (without even knowing there is already a
> > >    soft rotation done). So he will just add naively a vf transpose: this
> > >    will still work for him, except if you decided to drop the rotate
> > >    metadata from the filter: the transmux/transcode needs to keep a
> > >    maximum of information from the input.
> > 
> > I don't think this is the use-case we should care about.
> > (It sounds like "undefined behaviour" to me.)
> > 
> I don't know, I think it's better to make a clear distinction between soft
> and hard rotation. One does not imply the other, they are independent.

Well, I think there is rarely (never?) a use case for both.
So _ideally_ I would say the best thing would be to have these possible
1) -vf rotate=n:hard : read in the metadata rotate from the input,
remove it on the output, rotate by n + previous metadata rotate
2) -vf rotate=n:soft : do not do any processing, update or add
rotate metadata to correspond to the previous value + n.

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