[vlc-devel] [PATCH 3/3] swscale: scale the aspect-ratio of the output format

Rémi Denis-Courmont remi at remlab.net
Mon Mar 3 19:06:51 CET 2014


Le mardi 25 février 2014, 11:14:50 Felix Abecassis a écrit :
> 2014-02-23 15:44 GMT+01:00 Rémi Denis-Courmont <remi at remlab.net>:
> > By convention, conversion filters accept the format if they can do the
> > conversion and otherwise fail. Post-processing filters can modify their
> > input and output formats as they see fit. It really boils down to the
> > assumptions made by the different call sites: whether they take the
> > conversion for granted, or can add further conversion filters if the
> > output format is modified.
> I don't see when additional conversion filters would be needed if only
> the aspect ratio was changed.

With a given source resolution, source aspect ratio and target resolution, the 
target aspect ratio is mathematically fixed. So a mismatch sounds like a bug 
somewhere else.

Well in principles, a mismatching aspect could mean that cropping is 
necessary. But a well-behaving video output display should never request such 
an video format, as it could involve in black bars in *both* dimensions. The 
video output should instead place the picture correctly.

So I would guess either the video output is not computing the picture 
placement correctly, or the aspect ratio gets corrupted at some point while 
setting up the pipeline.

Rémi Denis-Courmont

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