[gst-devel] Re: gstreamer 0.2 and colorspace filter?

[Erik Walthinsen]

On Tue, 12 Jun 2001, Ryan Drake wrote:

> We were checking out gstreamer 0.2 and noticed that the colorspace plugin
> (required for mpeg playback) will not build without a library called
> "Hermes".  None of us have ever heard of this library, although it was
> easy to find on freshmeat.
>
> Just a suggestion:  Something like MPEG playback should probably work "out
> of the box".  Maybe it would be good to use whatever filter was in 0.1,
> and include it with 0.2, because if I recall MPEG playback worked fine
> without this library.
Yeah, I'm not too happy with this dependency either.  I'd much rather have
the core functionality work without any libs behind it, but then again my
preferred solution kinda does the same ;-(  The colorspace filter is only
needed if you don't have the Xv extension (XFree86 4.x and a card that
supports it), and thus has to be fast because it's doing what the hardware
normally does.  Now, there's a trick here.  Hermes only does RGB -> RGB
conversions, whereas MPEG video is in the YUV colorspace.  So what's
happening is that the colorspace filter is doing a software yuv->rgb
conversion, except I just confirmed with Wim that the colorspace filter
doesn't built at all if Hermes isn't there.  Whoops.  We'll fix that...

The longer term solution IMO is to utilize a library I'm building, or an
offshoot of it.  It's called libcodec right now, and contains highly
hand-tuned kernels for various codec-related operations, mostly focusing
on MPEG motion compensation, iDCT, and colorspace conversion.  It's got
many versions of each routines, hand optimized for different processors
(P5, MMX, SSE, etc.).  That's what I want to replace Hermes with
eventually, or even fold Hermes into that lib.

> Otherwise, gstreamer looks like it's coming along really nice!
Thanks ;-)

      Erik Walthinsen <omega at temple-baptist.com> - System Administrator
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