[LAU] synchronization of two RME MADI cards

[Giso Grimm]

Dear linux-multichannel-audio-users,

we are running a setup with two RME MADI cards to drive a system with
approx. 100 playback channels. We are using jack2 and zita-j2a to
achieve a sufficient number of playback channels. The sample clocks are
synchronized via word clock, therefor the resampling is deactivated in
zita-j2a.

On a similar setup (with two different card types) I noticed that the
latency between the cards is fixed as long as jack/zita-j2a is running,
however, the latency differs between starts of jack. This seems also be
the case in the setup with two MADI cards.

Is there a way on the software side to solve this problem? Or is there a
way to measure the latency without access to the analog I/O (knowing the
latency every time would be sufficient)? How are other people solving
synchronized playback of >64 channels?

Best,

Giso