[Arm-netbook] Sorry state of Linux hardware video decoder libraries / lack of single API

[Roman Mamedov]

On Mon, 25 Jun 2012 15:03:52 +0100
Gordan Bobic <gordan at bobich.net> wrote:

> > In other words: GNU/Linux O.S has too many multi-media frameworks,
> > which makes it difficult to develop decoder drivers for various
> > low-power chips (including ARM SoCs).
> > This is not a problem for the powerful Intel x86 CPUs, as they can run
> > HD video in software, so having dozens of MM-frameworks  works for
> > them.
> 
> I'm not convinced it works for them, either. Scaling HD video (e.g. if 
> you have a 1080p video and blow it up to full screen on a 2560x1600 
> monitor) without accelerated GPU drivers even on x86 doesn't produce 
> passable results.

Don't confuse hardware video decoding(e.g. feeding the GPU with H264 data and
having them decoded) with just simple Xv support, which accelerates the
scaling you mentioned.
http://en.wikipedia.org/wiki/X_video_extension
http://www.x.org/releases/X11R7.5/doc/videoproto/xv-protocol-v2.txt

On x86 there's no problem having working Xv on almost any video card, and with
it the video scaling is offloaded from the CPU to the video chip (I am not
even saying "GPU", because many videocards from even before that term was
coined do support Xv).

We don't have Xv support on most/all ARM SoCs, in fact from what I see many of
them are even limited to using the fbdev driver while in X11. And without Xv,
even SD videos will play like a slideshow, because a lot of basic things like
scaling have to be done in software.

Of course it can be argued that maybe Xv is not even needed and an OpenGL
output should be used to accelerate things like scaling. Maybe this is indeed
the right approach, but from the x86 experience OpenGL output in video players
typically is clunkier and slower than Xv and puts more load on the CPU. Not to
mention that there's probably a lot of apps which will expect Xv support and
not something else to be present, to play videos in a reasonably fast manner.

-- 
With respect,
Roman

~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Stallman had a printer,
with code he could not see.
So he began to tinker,
and set the software free."
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