Subject: Re: [linux-audio-dev] LADMEA Prototype
From: Paul Davis (pbd_AT_Op.Net)
Date: Fri Aug 10 2001 - 01:16:27 EEST
I'm in a tremendous rush to get out the door, but I can't help
commenting on 2 very basic ideas.
>clients). I should not be too hard to build exchange links using GStreamer,
>LAAGA, ATM and aRts. It should be easy to write new clients or wrap existing
If LAAGA/JACK is not the inter-process media exchange/sync API that
takes off, I will see zero point in pursuing it.
>real time and offline processing. All of this should be possible without
>either the client or exchange knowing what they are connected to. Hopefully
>it should be possible for the exchange to be in-process, in an external
>process or on a remote machine and exchanges do not need to know what data
>they are handling (although this can help).
In casting a glance over the API *massively* complex for no particular
reason I can discern), I notice this idea of an "exchange" being
central.
As I understand it, LADMEA is still driven by the same kinds of ideas
that GStreamer and GLAME use: a network in which various components
asynchronously push and pull data around. In LADMEA a client calls the
"sendToExchange" callback on an exchange, and in all probability, the
exchange will call various "sendToClient" callbacks. This is how data
is moved from A to B.
If I've misunderstood the proposal, excellent. Otherwise, I don't
believe that such a system can work for the proposed cases of
real-time/low latency applications inter-operating with sample sync. I
believe this for all the reasons that arose during the discussion
Richard and I had about GLAME's model.
Summarised, thats because to work in the way expected by users (and
quite reasonably so IMHO), the "network" needs to be driven by a
uniform, overarching "clock" that ticks universally for every node. A
node may choose to do nothing on a tick, but it must be "called" and
return synchronously at each tick. Any system based on a model like
"sendToExchange" and "sendToClient" will, I think, be susceptible to
the same kind of network halting problems that GLAME can encounter,
though within GLAME, this is arguably a feature rather than a problem.
In LADMEA, the problem is slightly the reverse of the one in GLAME,
since LADMEA appears to use a push-to-whoever model, rather
than a pull-to-me model. But the same basic issue still applies. I
think.
Did I misunderstand something?
--p (back on monday, august 13th)
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