IAX inbound calls and intermittent audio in VM recordings

We’re experiencing severe audio problems with voicemail recordings on our Asterisk servers: when inbound calls comes from an IAX trunk, the recorded files are missing the audio signal in a range of fractions of a second up to several seconds. All the others system communications are crystal clear…

Tested with 1.4.19 and 1.4.21…(I’ve used wav and wav49 alone, then the two formats together…)

Call comes from SIP trunk (alaw/g729) -> voicemail sound OK
Call comes from IAX trunk (alaw/g729, trunk=yes/no) -> voicemail unhearable

I’ve made a “top” to see if the load was two important…everything OK.

I’ve made a “iax set debug jb” to see if packets were lost…no packets lost

I’ve noticed that when we put a continuous sound in the recording (like the music on hold) there is no blank…so I’m suspecting something like the voice activity detection. How can I disable it in IAX.conf, or have you some clues?


Update : it seems that my providers uses v1.2 asterisk client!

Could it be a bug from the 1.2 version?

It seems that the silencethreshold parameter of voicemail.conf is involved…

When I talk quietly, the problem occurs…when I talk loudly or if I put music on hold, sound gets recorded fine.

What is the max value for the silencethreshold parameter and how can I solve this kind of problems? Thanks…