[asterisk-users] G729/MOH Quality

[Steve Underwood]

Darryl Dunkin wrote:
> Does anyone have any opinions on the music on hold quality over G729?
> The stock files seem to sound terrible over it, this is enhanced further
> by calls coming from the PSTN via a Zaptel gateway. I am only using the
> stock wav files and have not attempted to use much else so far.
>
> I've ruled out timing issues on the system generating the MOH itself
> (ztdummy on the PBX itself, our Zaptel gateway is a separate Asterisk
> server). There is no transcoding going on in the middle except via our
> Zaptel/T1 gateway. When using G711 it sounds fine of course, but this
> doesn't work well for remote sites with lower bandwidth connections.
>
> As of now, I'm torn between getting complaints from end users about the
> music or killing it entirely (leaving people waiting in queues with dead
> silence).
>   

Music over G.729, or any other similarly low bit rate codec sounds 
bloody awful. The only thing you can do to mitigate this is choose 
simpler music. A single voice singing sounds OK - that's what the codec 
is optimsed for. A singer with a guitar doesn't usually sounds too bad. 
As the music gets more complex it goes horribly downhill from there.

Steve