[TriLUG] IP Phone

[Rob Lockhart]

Jon I meant to ask you a question at the last meeting, but it is perhaps
a bit technical in nature.

How does the VoIP system handle POTS sample rate recovery and NTR for
sampling over an IP network without such capabilities?  Otherwise, I
would assume that things like Tivos and such (you have to have a land
line for unhacked DirecTivo) that require POTS modem access for
pay-per-view and other such things would not work reliably (due to a
high connect rate causing a high bit-per-symbol allocation) the QAM
signalling getting screwed up by the irregularly-arriving packets.  I
could even imagine that, say, network latency being very low and
consistent during training, and then a few seconds later having
different latency (or jitter) characteristics than during training, that
this may cause the CPE modem to train up at a higher rate than the VoIP
system can compensate for, thus it may cause the narrowband modem link
to drop and attempt retrain.

Just curious....

Of course this is very hard to detect with your ear and the right
decoding/encoding techniques but I doubt they'll work very well for a
33.6kbps or higher connect rate (due to the density of the constellation).

Regards,
  -Rob