[linux-audio-user] Outputting same sound source to multiple cards simultaneously

[Paul Davis]

On Wed, 2007-01-10 at 08:38 -0800, reuben firmin wrote:
> On 1/10/07, Sampo Savolainen <v2 at iki.fi> wrote:

>         Just imagine two wall-clocks. Can you really expect them to
>         keep the exact
>         same time over years of continuous running without anyone
>         re-setting them?
> 
> 
> If they were hardware being run by the same software on the same PC
> then, yes, I would expect them to (be made to) stay in sync,
> regardless of their mechanical quirks. 

but the audio interfaces are not "being run by the same software".
control over how they see time belongs to the clocks on each interface.
the PC cannot control the clocks in anyway. this is why if you want
things to stay in sync, you must share a clock.

note: one of the very first tasks in designing any kind of digital audio
installation that involves multiple devices (of any kind) is to
determine what the clock sharing network will look like. getting it
right is critical. the fact that these cards share slots on the same bus
doesn't remove the issue.

--p