[Asterisk-Dev] chan_zap.c:4409 my_zt_write Major Probs

[Andrew Kohlsmith]

On May 11, 2005 11:13 pm, Russell Bryant wrote:
> Yes, exactly.  It IS a debug level message.  It was changed to an error
> by mistake.

I've been following this and doing some of my own testing as well, and I'm 
curious about several things.

> The conditions that make this message come up are not a sign of problems
> with your Zap stuff.  It can happen when there is jitter on your
> network, and given that you were using a WiFi phone, I'm sure that is
> the case.  Also, note that the "audio may have been lost" part was a
> part of the change to be a warning, not the original debug message.

my_zt_write() attempts to send audio data to the zaptel hardware to get it out 
to the PSTN.  Now there are (by default) 4 buffers to which pending data can 
be written.  Increasing the number of buffers by adding "jitterbuffers=8" to 
zaptel.conf seems to help (by allowing the driver to queue up more audio, 
which can cause increased latency), but the failure is still curious.

If there is network jitter or delays in getting data from the network in a 
timely fashion, then that means that zaptel already played blank audio out to 
the PSTN, and the data that came in late will have been discarded.  I don't 
believe that "audio may have been lost" is incorrect at all.

While I don't think that this message belongs in DEBUG land, perhaps it would 
be a better compromise to have a proper reporting layer which can help people 
see where problems may be.  IAX2 already has the new jitter buffer and iax2 
network statistics reporting, perhaps something similar for zaptel 
(statistics) would be a good thing.

Please feel free to correct me on any of this.

Regards,
Andrew