На 27.05.11 07:46, Kertesz Laszlo написа:
I have a few questions regarding the audio/video codecs used in
1. How does the codec negotiation work between 2 jitsi clients if
they have different codec order?
We would most likely end up using the first codec from the answer as
recommended by RFC 3264. Your experience may vary from one application
to the other though as it is generally recommended for an answerer not
to change the order from the offer unless they really need to.
Keep in mind that situations where each party streams in a different
codec are also perfectly valid so you may also end up with something
2. There are many codecs there, is there a detailed list about them?
All the codecs we support are listed in the audio and video preferences.
3. Why do some codecs not support zrtp?
They don't. ZRTP is completely codec agnostic.
For example, the GSM codec
(that by the way has the lowest bandwidth usage,3-4 KB/s) does not
support it it seems (ilbc, speex, dvi/4, pcmu/pcma supports zrtp).
Is it possible that because of the codec your SIP server made you use a
different media path? Do you reproduce the issue with XMPP?
4. Why telephone-event is listed as a codec? Or is it a codec?
It is not, in the sense that it does not allow encoding or decoding
media. It is however one of the RTP payloads that we may end up
streaming if the user sends DTMF events.
Because i had to disable it in order to be able to use certain IVRs,
if it was enabled, those IVRs (most of them) did not work. (My SIP
account has dtmf info set from the server.)
This happened to me once too. Some IVRs return telephone-event as their
highest preference codec. Jitsi tries to use it and fails. It's a bug
with simple workarounds. It would probably be best to open a ticket
5. What is the purpose of the h263-1998 codec? It produces very
blurry images, it seems unusable.
Some devices only support h.263 and some users prefer low quality rather
than no video at all.
Hope this helps,