On 3 Oct 2007, at 10:16, Mark Quitoriano wrote:
>
>
> On 10/3/07, Tilghman Lesher <[EMAIL PROTECTED]>
> wrote: On Tuesday 02 October 2007 16:55:52 Brian West wrote:
> > On Oct 2, 2007, at 4:42 PM, Mark Quitoriano wrote:
> > > anyway still if there's a hack for meetme to work with g729 codec
> > > this won't be an issue. So is there a hack or patch that i can use
> > > any codec for meetme? tnx
> >
> > You still do not understand. It doesn't matter if the call
> coming in
> > is g729 you must transcode it to signed linear, mix the frames and
> > then code it back into g729 you end up with quality loss doing that.
>
> Or, in other words, you cannot mix compressed data. You must first
> decompress the data for mixing, then recompress it for transmission.
> During both operations, there is a potential for signal degradation.
>
>
> yeah i still don't understand. this is what i want to do. I want
> asterisk not to compress and decompress codecs. so either i can use
> SLIN as my codec for my SIP or IAX. or i can remove SLIN codec in
> meetme and change it to g729a so there's is no compression and
> decompression.
>
> do you get what i want to do? Thanks!
Not exactly.
Here are the facts:
meetme mixes in SLIN.
Any data arriving in anything other than slin will get transcoded
twice,
once on the way in and again on the way out.
Now some opinions:
The more efficient the compression of the codec, the less well it
copes with
decoding and re-encoding. Ulaw and Alaw are simple and not that
efficient,
but you don't lose any more by re-encoding than you did by decoding
in the first place.
Tighter codecs like 729 and GSM you will definitely hear the
difference.
Theory:
If you have a conference where there is only _ever_ one speaker
at a time, you could (in theory) optimize meetme to do without
mixing, and if all
the participants were using the same codec, you could get away with
not re-encoding
by sending out the appropriate incomming packet to all (other) members.
I'm guessing that isn't the case for you.
Advice:
use Ulaw - it's a decent tradeoff for this sort of thing.
Tim.
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