[Ffmpeg-devel] v4l2 arbitrary field order support

Richard Khoury richiek
Wed May 31 02:31:50 CEST 2006


> I am all for this change; I just need to test it on some other
> distribution and then I'll commit it (it seems that every linux
> distribution likes to break v4l2 compilation in new ways :).
> I tried to answer your first mail about this subject, but my mail
> bounced; sorry for the delayed answer
> 
Awesome, thanks Luca.

> Yes, I did that because I expect PAL or NTSC video to be always
> interlaced.
> Of course the situation can be improved and if there is some way to make
> this flag configurable, I'll be happy to commit the necessary changes.
> 
> > I can't quite see a nice way to add arbitrary
> > field order support without adding an extra field to the
> > AVFormatParamaters structure. Is there another way I can be doing
> > this?
> Well, adding an extra field to AVFormatParamaters is the only way I can
> see... Maybe someone who knows the libavformat API better than me can
> suggest another way?
> 
AVFormatParameters looks like the only interface we can use, so the
question is what is the best way to do it. I'm trying to think of a
generic way that could be beneficial to other format users and the
only thing I can think of is using a bunch of "user" void pointers at
the end of the AVFormatParameters structure that each individual
format can interpret in their own way. A new configuration structure
could be defined within v4l2.c that we can populate and assign to the
void pointer and that the device_init() function can accept as an
argument.
 ... it's that or we add one varaible specific for v4l2 grabbing to
the AVFormatParameters structure (not generic or extensible).

What do you think?


RichieK.





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