On Wed, 27 Nov 2002, Paul Davis wrote:
> i see this as more promising than the approach i think you are
> thinking of. you can't avoid the context switching - they *have* to
> happen so that the apps can run!! the question is *when* does it
> happen ... in JACK, they are initiated in a chain when the interface
> interrupts us. in the mserver model and/or the shared mmap'ed buffer
> approach, they just have to happen sometime between interrupts
> (otherwise the buffers are not handled in time). so there is no
> avoiding them, its just a matter of when they happen. the point of
> JACK's design is to force sample sync and to minimize latency - always
> generating and processing audio as close to when it is handled by the
> hardware as possible (hence the default 2 period setting). a model
> that allows the context switching to occur "sometime" between
> interrupts is more relaxed, but loses sample sync and slightly
Note that "sometime" means in same time as jack invokes the clients. The
r/w applications blocks at the r/w or poll point, so they will be
activated when the condition for the ring buffer is matched. Thus for 2
periods - conditions are same as for jack.
Anyway, as Kai stated, we are reaching a consensus that both ways are
useful for some cases.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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