[asterisk-users] Jitterbuffer issues

When initiating a call from a SIP phone to another SIP phone through Asterisk 1.4 (latest SVN), I get the following:

 

[Nov  2 10:08:55] WARNING[7292] abstract_jb.c: Failed to put first frame in the jitterbuffer on channel 'SIP/5001-08266108'

[Nov  2 10:08:55] WARNING[7292] abstract_jb.c: Failed to put first frame in the jitterbuffer on channel 'SIP/5000-08299448'

[Nov  2 10:08:55] WARNING[7292] chan_iax2.c: Resyncing the jb. last_delay 0, this delay -309029745, threshold 1000, new offset 309029745

[Nov  2 10:08:55] WARNING[7292] chan_iax2.c: Resyncing the jb. last_delay 0, this delay -374875680, threshold 1000, new offset 374875680

 

First is a question about why, when the channel is initially created, does the jitterbuffer fail to put in the first frame.  Here is the output from the console that shows more detail:

 

    -- Called 5000

    -- SIP/5000-08299448 is ringing

 Extension Changed 5000 new state InUse for Notify User 5002

    -- SIP/5000-08299448 answered SIP/5001-08266108

[Nov  2 10:08:55] WARNING[7292]: abstract_jb.c:469 create_jb: Failed to put first frame in the jitterbuffer on channel 'SIP/5001-08266108'

    -- adaptive jitterbuffer created on channel SIP/5001-08266108

[Nov  2 10:08:55] WARNING[7292]: abstract_jb.c:469 create_jb: Failed to put first frame in the jitterbuffer on channel 'SIP/5000-08299448'

    -- adaptive jitterbuffer created on channel SIP/5000-08299448

[Nov  2 10:08:55] WARNING[7292]: chan_iax2.c:794 jb_warning_output: Resyncing the jb. last_delay 0, this delay -309029745, threshold 1000, new offset 309029745

[Nov  2 10:08:55] WARNING[7292]: chan_iax2.c:794 jb_warning_output: Resyncing the jb. last_delay 0, this delay -374875680, threshold 1000, new offset 374875680

 Extension Changed 5001 new state Idle for Notify User 5004

 Extension Changed 5001 new state Idle for Notify User 5002

 Extension Changed 5001 new state Idle for Notify User 5000

    -- adaptive jitterbuffer destroyed on channel SIP/5000-08299448

  == Spawn extension (macro-stdexten, s, 8) exited non-zero on 'SIP/5001-08266108' in macro 'stdexten'

  == Spawn extension (macro-stdexten, s, 8) exited non-zero on 'SIP/5001-08266108'

    -- adaptive jitterbuffer destroyed on channel SIP/5001-08266108

 

 

As can be seen, the jitterbuffer is created after the first failure.

 

Second question, why is chan_iax2 involved in a SIP to SIP connection?  Is chan_iax2 required for the new jitterbuffer?