Subject: Re: [linux-audio-dev] LADSPA/parameter updating?
From: Paul Davis (pbd_AT_Op.Net)
Date: Sat Jul 14 2001 - 16:05:23 EEST
>>however, you can only access port buffers during your client's
>>process() callback - access at any other time is either "undefined" or
>
>How the control thread is launched and at what time?
>How and when it is run? And with what priorities/scheduler?
Which control thread? The one you create to monitor (for example) MIDI
I/O ? If so, then its up to you. LAAGA doesn't care about it in any
way (unless you give it higher sched priority than the LAAGA
engine/server - that would be bad, probably, perhaps).
Or are you talking about the thread that the LAAGA library creates on
your behalf? If so, then its created when you call laaga_activate(),
and its scheduling characteristics are controlled by the LAAGA
server/engine (since it must essentially act on its behalf). In a
low-latency situation, the thread would be running with SCHED_FIFO
scheduling; in other situations, it would have normal scheduling. In
both cases, it runs with a priority at least 1 less than the LAAGA
server/engine's audio thread. The thread is woken by the LAAGA
server/engine, either directly or indirectly, currently via a FIFO. It
spend most of its time asleep, waiting for data on the FIFO, and when
its done, it writes data to a second FIFO (which drives the next node
in the processing graph).
The operation of this thread is intended to be transparent to you,
except that its where your process() callback will be executed from.
>I cannot give examples now because I have not yet got the whole
>picture of LAAGA.
Unless you need to be involved in the implementation of a LAAGA
engine, thats the idea :) It doesn't include an "S" for simple, but
its intended to more or less opaque to an application developer, who
needs only a very simple API to use it.
But more seriously, I do need to draw some pictures of the current
design/implementation.
--p
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