[gst-devel] colorspace conversion

[Thomas Vander Stichele]

On Tue, 2004-02-17 at 18:30, Ronald Bultje wrote:
> Hi,
> 
> On Tue, 17 Feb 2004, Thomas Vander Stichele wrote:
> > Is there someone who has some documentation on our handling of
> > colorspaces ?
> 
> docs/random/mimetypes or the plugin writer's guide, the 'types' section in
> advanced. I'd suggest the latests, it looks better.
> 
> > Second, any recommendations on what to do to have an RGB-to-YUV
> > element ? I found some simple formulas on the net to do the
> > conversion, and it seems to me that it would be wiser to have a
> > separate element for YUV-to-RGB so as to not make the code for, for
> > example gstcolorspace, more complicated.  I'm assuming we currently
> > don't handle the case very well were an element can handle A(x) ->
> > B(y) and B(x) -> A(y), but not B(x) -> B(y), since that would expose
> > A(x) and B(x) as pad templates on sink and A(y) and B(y) on src, while
> > the element itself only handles some conversions internally.
> 
> I'm seriously gonna cry if you even consider doing this.

Me too :) That's why I'm asking.

> * ffmpeg is highly optimized for many architectures
> * ffmpeg is well maintained by lots of people
> * ffmpeg receives a lot of testing and has been thoroughly bugfixed
> * ffmpeg does pretty much all formats except some uncommon RGB formats
> which are handled by hermes
> * ffmpeg works
> * we need ffmpeg for decoding pretty much any movie type anyway

I agree with all your points.  You are still, however, missing one - 
ffmpeg cannot be distributed by either GNOME (in source form) or by any
distribution (in binary form).  We need our player to work, however few
the formats it handles, from a distribution.

> Don't. Please. Don't. Please. I'll seriously cry and not send you
> christmas presents if you do this.

What exactly do you mean with "this" ? Write a colorspace convertor to
do rgb->yuv ?

> If you really want to, I wrote a bunch of CSP conv. routines which are in
> a libcolorspace-related bug in GStreamer/GNOME bugzilla. You could use
> that as a starting point. It includes patches for our LCS plugin to work
> with it, too. You need those two patches, latest LCS CVS (from codecs.org)
> and some more.
> 
> Bad things:
> * it's slow
> * I think RGB on LE is inverted because I misinterpreted masks by then. I
> never bothered to fix this.
> * no optimizations whatsoever, and it'll probably require some slight
> changes to use liboil or so to do this (Dave?)
> 
> Good things:
> * it handles very many formats already (any RGB format, plus +/- 5 YUV
> formats) ecause it's very generic
> * it's easily extendable

Any chance we could get you to finish your work on that ? :)

Thomas

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