Currently, the audio delay in BigBlueButton 0.71a is caused by the
Java-based transcoding of audio packets from nellymoser <-> mlaw
within red5phone. See FAQ.
http://code.google.com/p/bigbluebutton/wiki/FAQ#Why_is_there_a_delay_in_the_audio_when_I_use_VoIP?
This means, even when a BigBlueButton server running is running within
a LAN environment (no network latency, no packet loss), with only two
people on the server, the audio delay is still about 1.5 seconds.
We’ve been thinking about our approach to audio and realize we’re
trying to solve two problems at once: (1) quality and (2) scalability.
But the feedback from many is “what good is scalability if the audio
lag is still 2 seconds for small groups?” For many -- especially
when doing small collaboration or one-to-one sessions -- low latency
is the key.
Flash supports both nellymoser and speex. Recently, we’ve been
working on optimizing the use of 16 kHz wide-band speex within
BigBlueButton. Turns out, this significantly reduces the lag in
audio. Why? When using speex, red5phone does *no* transcoding.
None. It passes the packets straight through to FreeSWITCH, which
encodes/decodes the speex packets in native code.
We have setup a test server for you to try out the audio in
BigBlueButton using speex. This server is running an internal build
of BigBlueButton.
http://test.blindsidenetworks.com/
So, grab a set of headphone, login to the server, and give us your feedback.
A good way to determine the latency is to login *twice* (use two
browser tabs), mute yourself in one session, then speak. Your audio
packets will go to the server in one session and come back to you in
the other. The difference between your speaking and hearing is the
latency.
There are still more problems to solve, and there is no free lunch.
Encoding speex is CPU intensive, so you’ll find FreeSWITCH taking more
CPU as the number of users increase. The Flash client is still using
restricted to transmit using TCP, which means if there are corrupted
packets, the user’s client will resend corrupted packets, and these
resent packets may arrive too late and be discarded as FreeSWITCH
attempts to keep the user in sync.
We look forward to your feedback as we keep exploring ways to improve the audio.
Regards,... Fred
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Not at the moment.
The good folks at Generic Conferencing paid an external consultant to
add speex support to app_konference, the conference module used by
BigBlueButton in Asterisk, but we've not tested our changes with
Asterisk yet.
Regards,... Fred
Our plan is to schedule a specific time in the near future, invite
everyone on the mailing list to join at that time, and watch the
server load.
We're thinking Tuesday, March 22, at 9-10am EST.
Regards,.. Fred
Vittorio Scarano
--
_____________________________________________________________________________
Vittorio Scarano
Dipartimento di Informatica,
Università di Salerno, Fisciano (SA) -- 84084 ITALY
E-mail: vit...@dia.unisa.it
Homepage: http://www.dia.unisa.it/professori/vitsca
ISISLab: http://www.isislab.it
Phone : +39 089 96 9733 (office), 9308 (ISISLab 1), 9307 (ISISLab 2)
Fax: +39 089 96 9600
We don't give out estimates for delivery dates. We release on
quality, not dates.
However, you'll know when we're getting closer to a delivery for 0.8
when we start our testing cycle. During the testing cycle, we shift
our focus to stability and bug fixing. For an overview of our
development and testing process, see
http://groups.google.com/group/bigbluebutton-dev/browse_thread/thread/8fc2360646bc6a09
We're not there yet for the testing cycle for BigBlueButton 0.8, but
working hard towards it.
Regards,... Fred
I confirm a very positive test in the last few minutes, with 4 people.
No noticeable audio lag.
Congratulations to all involved!
Best regards,
M ;-)