[vlc-devel] yuv<->rgb conversion in video filters

[Kaarlo Räihä]

http://mailman.videolan.org/pipermail/vlc-devel/2007-August/033423.html

Someone already has done something like that, but I don't if it will work.

Branko Kokanovic kirjoitti 08.08.2009 kello 13:24:
> Greetings,
> I wanted to write simple filter - posterize (idea from VLC wiki that
> points to http://www.movavi.com/videoeditor/filters.html)
> 
> Anyway, I need to work in RGB domain to achieve this effect and I don't
> want to write my own yuv<->rgb convertions. I looked at several places
> and it all ended without answer, so I had to ask here. Short question
> is: what is best practices for this? Long questions are:
> * should I convert pixel by pixel or whole frame?
> * can I use filters in modules/video_chroma/ and how (references to any
> existing code should be enough) or we're not supposed to directly access
> these filters?
> * Is image_Convert function way to do it? (I looked where it is used and
> those are mostly some filters that doesn't need it for chroma
> conversion, but for some other purposes - resizing, croping, so -
> although tempting, I'm left wondering should I use it)
> * Finally, maybe filter developers shouldn't try to convert pixels to
> RGB domain at all (I don't see any filter that does/need that?) and I
> should try to implement posterize logic directly in YUV domain (maybe
> offtopic, but, mathematically speaking, even if I know minimum and
> maximum of YUV components, I will not be able (without conversion to RGB
> domain) to reproduce exactly same effect as in, for example GIMP).
> 
> P.S. Should I write this filter at all? Maybe it already can be achieved
> with some combination of existing filters that I'm unaware of?
> 
> Thanks for replies, Kokan
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