[gst-devel] TI OMAP DSP support

[g]

Stefan, Kalle, Felipe

Thank you all for your help.

So it is as I expected re. DSP support in GStreamer.
Someone in another group had said that GStreamer
supported the DSP for the N810 and then I found the TI
article on the GStreamer site so I was seeking
confirmation.

The information about bandwidth to the screen is
useful.

I think the N810 is a bit more powerful than the N800.
I guess the next steps for me will be to write a
simple test that simply refreshes the screen as
quickly as possible to confirm the screen bottleneck.
Next will be to try and implement iDCT on the DSP.

g.

--- Stefan Kost <ensonic at hora-obscura.de> wrote:

> hi,
> 
> Quoting g <the_ether2 at yahoo.co.uk>:
> > --- Josep Torra Valles <j.torra at telefonica.net>
> wrote:
> >> First I think that you should get more knowledge
> >> about the N8x0
> >> architecture and the OMAP SoC in order to be able
> to
> >> understand the
> >> scenario for your project.
> >
> > My "project" is simply to decode MPEG video. As
> stated
> > previously the core elements I intend to use are
> > already available as plug-ins to GStreamer.
> >
> > My questions have been whether GStreamer already
> has
> > implemented any DSP acceleration and if not, what
> the
> > performance hit of their absence is compared to
> the
> > potential stated by TI.
> >
> GStreamer itself does not implement any for of
> hardware specific acceleration.
> A few elements use liboil which helps to benefit
> from usinf vector  
> operations of CPUs (MMX, SSE2, ...)
> 
> If you want to benefit from a DSP, you have to
> rewrite the codecs  
> using DSP nstructions. You cannot just recompile it
> for a DSP and you  
> cannot just runs some parts easily on a DSP. So
> nothing Gstreamer can  
> do here. You have to get codec implementations for
> the DSP in question  
> by yourself. Thats why using a DSP is so difficult
> and often projects  
> decide to better use the CPU and invest in good
> compilers.
> 
> Stefan
> >
> >> > ffmpeg and xvid are available as plug-ins for
> >> > GStreamer and presumably work on Maemo 2008.
> What
> >
> >> If just crosscompile you will have something
> >> working, but it doesn't
> >> mean that the performance will be enough to get
> VGA
> >> at 30 fps.
> >
> > As stated above, the MPEG decoders ffmpeg and xvid
> are
> > already available as plug-ins for GStreamer. I
> have
> > merely asked what the performance is. Maybe
> someone
> > has already optimised one or both of these for ARM
> and
> > / or the DSP portion of the OMAP2420.
> >
> > As previously mentioned, a TI article specifically
> > states that there is a GStreamer plug-in that uses
> the
> > DSP and yet I cannot find any mention of its
> existance
> > on the GStreamer site.
> >
> >> I also wrote some assembly to accelerate video
> >> decoding on ARM5e and
> >> ARM6 cores and I think that probably on ARM6(400
> >> MHz) you can achieve
> >> more video decoding speed than using the DSP(133
> >> MHz).
> >
> > The clock frequency isn't the only part. What
> matters
> > is what work is done per cycle. The DSP obviously
> has
> > an important part to play. That's why it's there
> in
> > the first place. Given the choice, doing all the
> > processing purely on the ARM core and not using
> the
> > DSP for any task is silly - especially for video
> > decoding.
> >
> > g.
> >
> >
> >      
>
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