Codec g729

[Giordano]

Hello everyone,

I am a fresh BBB user, I'm trying to customize it a bit to adapt it to
the needs of my company.
I must say that it is an amazing piece of software, very well
organized and very well documented. Kudos to the developers :)

I was wondering if it was possible to make BBB to use the g729 codec
for audio encoding.
I found this guide http://asterisk.hosting.lv/#bin and I used it for
installing the codec and enabling it in Asterisk.
The codec seems to be loaded correctly by the software (I checked with
the command "core show translation recalc 10") however the audio does
not work, namely if I enable the "headset" when using the flex client,
I can hear no sound :|

I checked google some more and I found this message in this same group
http://groups.google.com/group/bigbluebutton-dev/msg/09fd03d2f031fcee
Quote: "We can, but there is more work that needs to be done on the
red5 voice app to support it. " (about enabling g729)

My questions for you are:
1) has something changed since January, namely is now possible to use
g729? What do I need to do to use g729 instead of ulaw?
2) Is there any other codec with better compression(=less bandwidth
used) alternative to g729 and ulaw that I can use?

Thanks in advance!

Giordano

[Fred Dixon]

Hi There,

At the moment, Flash doesn't support g729 codec for encoding/decoding
audio. You can see the list of supported codecs here:

http://en.wikipedia.org/wiki/Adobe_Flash#Flash_Audio

Flash supports speex. As of BigBlueButton 0.71, we added support for
the speex codec; that is, you can specify in the BigBlueButton server
to accept audio in speex format from the Flash client.

However, we found that while the bandwidth is lower, there is a much
larger CPU requirement on the FreeSWITCH/Asterisk server to
decode/encode speex. It turns out that the audio and scalability is
better using nellymoser instead of speex.

Of course, as Flash supports other audio codecs in future versions,
there will be more options for BigBlueButton.

Regards,... Fred

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[Giordano]

Thank you for the thorough explanation.
we have some bandwidth issues, thus I'll give speex a try :)
Have a nice day!

Giordano

[Giordano]

Hi, one more thing ^^

I'm trying out speex. I proceeded as follows:

1) Switched to freeswitch instead of asterisk:
# bbb-conf --conference freeswitch

2) I modified the file /opt/freeswitch/conf/vars.xml and changed the
lines (as suggested in the comments in the file) in the sequel from:
<X-PRE-PROCESS cmd="set"
data="global_codec_prefs=PCMU,G722,PCMA,GSM"/>
<X-PRE-PROCESS cmd="set"
data="outbound_codec_prefs=PCMU,G722,PCMA,GSM"/>
to:
<X-PRE-PROCESS cmd="set"
data="global_codec_prefs=speex@16000h@20i,speex@8000h@20i,G7221@32000h,G7221@16000h,G722,PCMU,PCMA,GSM"/
>
<X-PRE-PROCESS cmd="set"
data="outbound_codec_prefs=speex@16000h@20i,PCMU,PCMA,GSM"/>

3) restarted BBB

Can you confirm that this is all I have to do? How can I be sure that
BBB is using speex (apart from the CPU usage jumping up eh eh :P) and
not another codec?

Thanks :)

Giordano

[Richard Alam]

You should see in the /usr/share/red5/log/sip.log that it is using
SPEEX and also in the client log.

Regarding G729, there is code in BBB that will transcode Nelly to G279
and back. However, there's a little bit of work to make use of it as
right now it assumes that is will only work with PCMU/PCMA and SPEEX
WB. And I think G729 needs a license in Asterisk/FreeSWITCH.

Currently we are working on improving voice delays. We have identified
a few areas that introduce the delays and are trying implement ways to
reduce them.

Richard

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BigBlueButton
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http://code.google.com/p/bigbluebutton

[Giordano]

Ok thanks for the helpful information :)

Giordano