Re: Word synchronization of multiple PowerMACs audio outputs
Re: Word synchronization of multiple PowerMACs audio outputs
- Subject: Re: Word synchronization of multiple PowerMACs audio outputs
- From: Matthew Xavier Mora <email@hidden>
- Date: Thu, 24 Jul 2008 13:21:30 -0700
On Jul 24, 2008, at 12:03 PM, Jeff Moore wrote:
My expectation was that the clock for the outputs would be derived
from the digital input, and this will keep the outputs in sync
(some sort of switch would occur in the h/w that would use the
input word clock instead of the internal one).
It does not seem to be working, there is drift, the same drift as
with decoupled machines.
Setting the master device for the aggregate device doesn't change
the hardware clock the underlying device is using.
At any rate, my understanding of the built-in digital ins and
digital outs on our devices is that the inputs will always lock to
the incoming clock. Generally, the digital outs are self clocked,
but there may be specific models where they are able to be driven by
the clock on the input. I can't remember any off the top of my head,
but I'd have to ask to be sure.
The HDA codecs do not have the ability to lock the audio output
(either analog or digital) to the incoming digital in clock. You would
need to use PowerPC macs to do what you want. PowerPC macs used I2S
codecs and a custom ASIC which allowed clocking the entire audio
system off the recovered incoming Digital In clock. Or you can add an
external audio card or use USB or FireWire device with word clock/
digital in. A plug for MOTU's driver here, MOTU's FireWire drivers
will allow you to run their FireWire interfaces locked to any audio
source on a Mac.
Hope this helps,
Matt
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