[Asterisk-Users] IAX voice distortion with full upload channel / SIP ok

[Koopmann, Jan-Peter]

Hi,

this is the scenario:

One * is placed in a central location with more than enough up/down
bandwidth. One * is placed behind a DSL 3000/384. Both * are linked via
IAX trunking. Everything is fine until the upload channel of the remote
site is filled with a download, then heavy voice distortion starts. Well
of course this is expected. So I fooled around with HFSC QoS scheduling
on the remote site Linux machine. The scheduling seems to work as the
TOS marked traffic is put in the correct queue and the upload bandwith
for other applications is going down.

BUT: The voice quality problems definatly stay when using IAX. The funny
part: Doing the same with SIP shows no big problems. SIP calls to
T-Online work nicely and even if I change the * <-> * link from IAX to
SIP everything is fine even with full up-/downloads on the remote DSL
connection.

My conclusion would be that this depends on the IAX implementation
somehow. I tried different settings for jitterbuffer, trunk and
trunktimestamp all with the same result. This currently means we go back
to SIP for *<->* linkage.

Any ideas? If I should rather post this over in -dev please let me know!



Kind regards,
  JP