synchronizing sound cards in a cluster

[Jim Lux]

Anybody have any good ideas on how to synchronize the sampling from 
multiple sound cards in a cluster using Ethernet as the interconnect. The 
application would grab data from the sound card (notionally at 100 
ksamples/second total, for two channels) and do a ton of signal 
processing.  At some point in the processing, the streams of data need to 
be shared between processors (i.e. to do beamforming), and so, needs to be 
time registered.
The bandwidth isn't a real challenge here (with, say, 16 processors, that's 
only about 32 Mbps total), nor is latency, but synchronization is.

One can fairly easily synchronize to a millisecond over Ethernet, but this 
application needs sync to, at worst, 1 sample time (20 microseconds) 
although order of a microsecond would be nice.



James Lux, P.E.
Spacecraft Telecommunications Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875