Re: [Jack-Devel] About ALSA drivers for Firewire sound devices

On Wed, Jan 29, 2014 at 10:22:59AM -0500, Paul Davis wrote:
> On Wed, Jan 29, 2014 at 10:06 AM, Takashi Sakamoto
> > 1. Daisy-caining
> > With FFADO backend, jackd can handle some firewire devices. But with
> > ALSA backend, jack can't. This rule is still applied to the new drivers.
> >
> > When users want to use several ALSA PCM devices for firewire sound
> > devices, they must write ALSA configuration with 'multi' plugin. See in
> > detail:
> >
> > http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html#pcm_plugins_multi
> 
> With non-clock-synced devices these days, it is better to use JACK's own
> capability for handling multiple devices. But since all the firewire
> devices on a chain share the same clock, this seems right.

While the firewire bus provides a synchronous bus clock (primarily used for
timing data transfers), very few firewire audio devices can make use of this
to derive an audio clock.  In a vast majority of cases, to achieve clock
sync two firewire interfaces on the same firewire bus still need to be
synced either via wordclock (best) or optical ports (the fallback in the
absence of wordclock I/O).

jonathan

1391034165.32551_0.ltw:2,a <20140129222215.GA2763 at marvin dot atrad dot com dot au>