Re: [linux-audio-dev] XAP spec - early scribbles

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Subject: Re: [linux-audio-dev] XAP spec - early scribbles
From: torbenh_AT_gmx.de
Date: Sat Mar 01 2003 - 13:13:21 EET


On Fri, Feb 28, 2003 at 09:01:21PM +0000, Dave Griffiths wrote:
> On Fri, 28 Feb 2003 19:05:19 +0100
> David Olofson <david_AT_olofson.net> wrote:
>
> > On Friday 28 February 2003 09.20, torbenh_AT_gmx.de wrote:
> > [...]
> > > random latency ? how do you mean that ?
> >
> > Latency depends on how you happen to construct the net (order of
> > instantiation, connections etc) and/or the actual layout of the net,
> > in "non-obvious" ways.
>
> In ssm I sort the network each time a connection is made/destroyed, and generate a ordered list of modules to process from the root up to the leaves. It has to cope with circular sections, which unavoidably introduce latency, but it works. It also automatically means unconnected modules don't get processed, which is nice.

how does ssm find out the latency it should impose ?

and at which position does it impose latency ?

>
> > > see current implementation...
> > [...]
> > > one advantage is with silent sub nets....
> >
> > I'm not sure it's that easy. What about plugins with tails and/or
> > internal state? (Delay, reverbs, most filters, ...) You can't just
> > stopp running these when they get no input, or when you don't need
> > their output.
>
> I must admit I haven't followed this discussion too closely, so you've probably covered all this before, but I think all this work to figure out if you are processing silent data is not really as much a win to be worth the hassle - as it won't ever make the worst case faster.

I would like to give as much control to the galan programmer as possible.
if all my plugins would be able to handle the silence case...
(i just noticed they dont when writing the last mail :)

with some event logic it is possible have mutually exclusive gains.
effectively making the worst case (subnet X running OR subnet Y running)

well but i think i would not consider this an argument if i were on your side :)

> Time would probably be better spent finding actual bottlenecks and optimising them.

i guess you are right...
we are all somewhat locked to our designs, i think...

Another problem i have with moving to the graph ordering side
is the opengl stuff in galan which requires the pull model for
the data.

It would get somewhat inconsistent if gl data was pulled and
audio data not... but this is also cosmetic...

-- 
torben Hohn
http://galan.sourceforge.net -- The graphical Audio language


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