[Asterisk-Dev] codec configuration thoughts

[James Golovich]

I've been trying to come up with a way to pass config options to specific
codecs (see bug #149) and I haven't run across anything that strikes me as
the best way to do it.  So I thought I'd share some of my thoughts and
maybe someone else will have some thoughts as well.

One idea I had was to allow the setup of codec classes, setup in something
like codecs.conf.  Each codec could have a numbered priority, or they
could be listed in order of priority.  Hopefully this would make it
possible to keep the existing way of handling things, but just add another
option.

[lowbandwidth]
disallow => ulaw
disallow => alaw
allow => gsm
allow => ilbc
allow => speex,B8V1a1D1
allow => speex,B15

The options would hopefully be similar between all codecs, but if its just
a string to be passed to the codec then it might make it easy.

My hypothetical options:
B6 = bitrate of 6kbits/sec (B2, B4, B6, B8, B11, B15, B18, B24 would be
valid for speex)
v1 = enable variable bit rate
a1 = enable average bit rate
c2 = set complexity (cpu usage) default is 2 (1-10 is valid)
V1 = enable VAD
D1 = enable discontinuous transmission
p1 = enable perceptual enhancement

Then in a user/peers configuration (in iax.conf,sip.conf,etc.) it could
have an option like codecclass => lowbandwidth.  In theory there could
also be a SetCodecClass application so the class could be changed by
extensions.conf

I really don't like the way this looks like it would work, but its the
best I could come up with.  Hopefully someone will have a better idea
about this

James