[Freeswitch-users] How to inspect the jitterbuffer?
Holger Freyther
holger at freyther.de
Sat Feb 11 02:31:33 MSK 2012
Anthony Minessale <anthony.minessale at ...> writes:
> You are pushing RTP up against TDM, RTP can start and stop, TDM
> cannot, When there is no RTP the TDM will carry on sending the
> IDLE_FLAG byte over the wire.
>
> I made both the RTP stack and the TDM endpoint from scratch so you
> should assume I may have some insight.
What I am arguing with... is that if I say a word like 'two' and
RTP looks a bit like this.
RTP:
Wall Time Seq.No Time 'Sound'
0.0 1 0 'T'
20ms* 2 160 'W'
40ms* 3 320 'O'
...
some skew 100 100*160 'T'
+20ms 101 101*160 'W'
+20ms 102 102*160 'O'
and on the remote it arrives as:
'TW(?)O'..'T'..'O'
something is wrong with the playback speed/queue/buffer of the
audio stack. All I ask for is (because I didn't see anything
in the wiki about that):
1.) How do I check if the jitter buffer is enabled on a call.
2.) How do I check if arriving RTP packets arrived too late for
the speed of the FreeTDM voice queue.
More details:
I started with a setup like this:
RTP/AMR -> FreeSWITCH (sangoma transcoder) -> FreeTDM..
For debugging I changed it to:
AMR -> FreeSWITCH -> RTP/PCMA -> FreeSWITCH -> FreeTDM.
(SIP on 5060) (SIP on 5062)
The idea was that the first FreeSWITCH has to deal with
the jitter and the second receives a clean linear in wall
clock time RTP stream. My sofia sip profile includes these
params:
<param name="rtp-timer-name" value="soft"/>
<param name="manual-rtp-bugs"
value="SEND_LINEAR_TIMESTAMPS|NEVER_SEND_MARKER|\n
IGNORE_DTMF_DURATION" />
<param name="rtp-rewrite-timestamps" value="true"/>
The resulting output of the frontend FreeSWITCH is not
linear though (so no idea what rtp-timer-name soft should
do):
But the resulting stream has packets like this:
P.No Wall Time Codec
723 12.761045 G.711 PCMA, Seq=18533, Time=90720
731 12.841107 G.711 PCMA, Seq=18534, Time=90880
so somehow the expected arrival time was 17.78 but it
ended up being 12.84 and I think FreeSWITCH/FreeTDM/STFU
do not deal well with that.
any ideas?
holger
* add a little jitter
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