On November 28, 2004 12:28 pm, Peter Svensson wrote: > One problem that has been / is being discussed in another mail thread is > that the cards are in fact not synchronized. After a while the internal > clocks on the cards will diverge a large enough fraction of a ms. If I > remember correctly there is only on ms worth of buffering where at least > two would be needed to handle all possible phase shifts between the > interrupts on two cards. > > Even if the two (or more) cards were made to drive their clocks at exactly > the same frequency they can still end up in different phases. Of course, a > more advanced clock servo loop can keep the 1kHz timer phase. This, I > feel, is where things get tricky.
Hmm -- So I suppose there is no mechanism to say "start collecting TDM data *now*" and then let the clock go at the whatever rate it's going at on the local card, picking it up whenever the interrupt occurs on the "master" clock card -- okay there will be some skew but I wonder how noticeable it really will be. This is, of course, all just generic hand-waving at this stage. :-) Similarly I'm curious as to what it would sound like if the cards did all run free and you just collected the 8 bytes of data when the master card was picking up its data -- you'd have some initial skew but after the first data 'pull' it shouldn't matter... they're all crystal-driven so the actual discrepancy between cards in the same case (i.e. at the same ambient and with the same power) would be on the order of a few (hundred maybe?) ppm -- hardly anything you'd notice in real life. -A. _______________________________________________ Asterisk-Dev mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
