[pjsip] Strange RTP receive issue in PJ-MEDIA

Benny Prijono bennylp at pjsip.org
Fri Apr 11 10:20:24 EDT 2008


On Thu, Apr 10, 2008 at 10:41 PM, Jeremy King
<jerry.ipe.thomas at gmail.com> wrote:
> Thanks for the RTP header tip! What was being printed wasn't making any
> sense!
>
> After my temporary timestamp generation patch, I can hear audio playback,
> which is great, but quality is bad. I tried the same call with X-Lite as
> well as SJPhone and audio was good. Is there something I need to or can
> change/tweak to improve PJ audio quality?

There is a problem if you use sequence number instead of timestamp to
feed the frame to jitter buffer, namely that you won't be able to
handle multiple frames inside one RTP packet. With G.711 codec, this
will happen all the time as the definition of G.711 frame is 10ms,
while normally an RTP packet contains 20ms worth of frame. So half of
the audio is lost!

As you said remote is sending RTP with timestamp equal to zero (all
the time). This is just wrong, and you must fix that instead of fixing
PJSIP. Frankly I don't care if any other softphones handle this, I'm
not bothered. :)

> I have attached the audio capture files for PJ, SJPhone and X-Lite
> annoucement playback for the same announcement. The attachment,
> 20080411014500_TS1.tar.bz2, is ~1.63 MB. I hope it doesn't get blocked.
>

It does. It's too big for this list.

Cheers
 Benny




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