[LAD] ALSA doumentation

Hannu Savolainen hannu at opensound.com
Sun Nov 16 22:14:32 UTC 2008

Fons Adriaensen wrote:
> On Sun, Nov 16, 2008 at 11:51:12AM -0500, nescivi wrote:
>> He needs to make this system autorecover from any accidental loss of 
>> external sync, since he will not be able to watch the control panel 
>> of one computer, let alone 16 or so. And he needs other people to be 
>> able to use and run the system, when he takes a break, or has more 
>> important things to do.
> That's correct, but only part of the picture. The system
> will be used in two roles, as a permanent installation
> in a museum, and as a research tool.
> In the first role it has to work unattended day after day,
> surviving power and network interruptions and everything
> else that could go wrong. All the museum staff will see
> is a 'player' like telecommand GUI on a computer at the
> reception desk. The system is on its own, and not only
> when I'm taking a break.
> In the second role it has to be completely flexible and
> reconfigurable. It should be able to resume the 'museum
> mode' with a single mouse click when the researchers are
> done using it. For this reason, they are not allowed to
> modify any physical wiring, and all signal routing
> including clock distribution must be under software
> control.
> In the future the system may be connected (by optical
> links) to other installations in the same building and
> also to a concert hall or recording studio a few km away.
> This again has to be remotely controlled, and of course
> may involves switching, among other things, some clock
> sources.
I see.

The original discussion was about how hardware features like MADI sync 
source selection should be exposed to applications. My answer was that 
it should not be exposed. It should be managed by the sound subsystem 
and the tools related with it. If this kind of "safe sync" feature is 
necessary in real life situations then it should not be business of the 
application to do it.

So the Wave Field Synthesis application should not care about where the 
sync comes. It must just assume there will be proper sync all the time.

Instead this kind of monitoring can be given to a dedicated program (if 
a simple shell script cannot do it). This keeps the actual application 
clean and reduces the risk that it doesn't work with a MADI card from 
some other manufacturer.

Best regards,


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