[gmpi] Re: on mutliple sample types (OT, but let's finish?)

  • From: Steve Harris <S.W.Harris@xxxxxxxxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Wed, 17 Dec 2003 10:24:55 +0000

On Tue, Dec 16, 2003 at 05:59:30 -0800, Chris Grigg wrote:
> >It's a GMPI plugin which hosts DSP-accelerated plugin(s).  The GMPI host
> >(the user app) passes buffers to the GMPI plugin.  The GMPI plugin converts
> >the data to the DSP accelerated data type, then runs all the contained
> >plugins.  When they are all done (it could be 1 or more plugins) the GMPI
> >plugin converts back to the GMPI native type (float?) and the GMPI host
> >continues.  Follow?  That could be done for each accelerated plugin, and
> >that is the easiest way to imagine it, but the sub-graph is a nice
> >optimization, I think.
> 
> I follow... but then the plugs in the sub-graph aren't GMPI any more. 
> (Which I guess you allow below.)  Don't care for that, seems 
> incomplete.

Agreed - and its outside/irrelevant to the spec anyway.

[OT] FWIW, I dont think we did reach consensus that dynamic port lists are
neccesary.
 
> >Efficiency IS a concern.  How does a native VST host run Powercore plugins
> >now?  My understanding was it does almost exactly this same thing, but on a
> >single-plugin at a time.
> 
> AFAIK that's right, but also unnecessarily inefficient since 
> float/fixed/float conversion, plus 2-way buffer passing across the 
> host/card bus, would have to happen at every single plug boundary.

IIUC it's not the float<->fixed conversion thats the burdon (relaisiticly
you have to do some kind of conversion there, but it will be pretty
quick, especially if its done by the DSP), its the extra bus traffic.
c.f.
http://www.techonline.com/community/tech_group/embedded/feature_article/7101

Doing some back-of-the-envelope maths, you can get something like 200
96k audio streams between a host and DSP card - assuming the bus is
otherwise unused. OTOH PCI-X is due to appear in PCs next year.

- Steve

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