[Asterisk-Dev] MELP and MELPe (1.2kbps) codecs for Asterisk

[Steve Kann]

Daniel Pocock wrote:

>
> Has anyone tried either of these codecs on Asterisk?
>
> There is a 2.4kbps (regular MELP) non-real time demo application (ANSI 
> C) here:
>
>    http://maya.arcon.com/ddvpc/melp.htm
>
> There are some MELPe specs and audio samples here:
>
>    http://www.compandent.com/products_melpe.htm
>
> Does anyone think this would be worthwhile or are there better 
> alternatives?
>
> The docs I've read so far claim that this codec is better than LPC10 
> in sound quality, uses less bandwidth, and approximately the same CPU 
> usage.

It does sound much better than LPC10, but:

1) It's patented and copyrighted: http://maya.arcon.com/ddvpc/melpread.htm

2) Presently, even IAX2 with 20ms frames has about 12kbps of overhead 
(IP,UDP,IAX2).  So for GSM you have about 25kbps.  Even using the 
magical 0bps codec, you still end up using 12kbps on the wire, unless 
you use larger frame sizes.  [IAX2 trunking, of course, helps a _lot_ 
where trunking is viable].

3) It's quality is probably not acceptable for commercial use;  It 
certainly does not approach uLaw quality..  sounds more like speex at 4kbps.

-SteveK