Hi,

thanks for all the ideas and suggestions. I think the amount of
possibilities got more and my blind spot got smaller.

I have to sort things out, but first I need to start some tests to get
real numbers. I will measure latencies and will check synchronicity
(if there is any).

In addition I will have to define some realtime constraints.
Fons, you wrote, that the delay should be within 0.5ms. Is this a good
value to stay away from the Haas effect? Maybe within 0.5ms precedence
the localisation is going to "smear"? Does anybody know anything about
it or is it a naive idea?

Thanks,
Sven Thebert

On Mon, Jan 28, 2013 at 3:23 PM, Fons Adriaensen <[email protected]> wrote:
> On Mon, Jan 28, 2013 at 10:14:48AM +0000, Dave Malham wrote:
>
>> On 28 January 2013 02:53, Ross Bencina <[email protected]> wrote:
>>
>> >
>> > How about deriving word clock from the AC power line? :)
>>
>>     That's probably the simplest solution for something that could use
>> local SD card players, though not for real time work. Keep the average
>> sample rate over a long period of time synced to the AC frequency
>> (doesn't matter if there is some drift due to distribution grid
>> loading, as all units should see this the same) and start time
>> controlled by a simple RF remote control system. They'll all stay in
>> sync and so long as the inter-unit delays are minimal (see Fons'
>> earlier email) it'll be fine for pretty well anything except perhaps
>> wfs
>
> Syncing to the power line would require relatively simple electronics
> (a simple very low BW PLL) and do the job nicely. If the sound card
> has software clock offset controls almost no extra HW would be required.
>
> The remove any remaining constant delay differences a simple solution
> would be to measure them, e.g. using a short linear sweep, and then
> send a correction to each unit. This could be entirely automated.
> Once done, all units would stay in perfect sync as long as they have
> power.
>
> Ciao,
>
>
> --
> FA
>
> A world of exhaustive, reliable metadata would be an utopia.
> It's also a pipe-dream, founded on self-delusion, nerd hubris
> and hysterically inflated market opportunities. (Cory Doctorow)
>
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