[Freeswitch-users] Codecs and things

[Steve Underwood]

On 12/23/2009 04:55 AM, Ahmed Naji wrote:
> Hello people,
>
> Can someone please clear the following ambiguities with codecs:
>
>    1. Are we definitively able to run pass-through codecs (e.g. G.729)
>       in Proxy Media mode, or does FS need to be running in
>       bypass-media ? the Wiki is not clear in this regard
>    2. When an A-leg has negotiated a pass-through media codec, can the
>       B-leg be transcoded into a non-pass-through codec, and
>       vice-versa ? think A-leg incoming with a G.729 codec, and target
>       for B-leg needs to be setup with a GSM-codec, say
>    3. Where in the developer's set of documentation are codecs
>       discussed ? I would like to start porting some code of mine for
>       G.729a/b/ab form a ti DSP platform to FS. FS lacking full G.729
>       support is proving quite a hindrance, and there is no clear
>       direction from the dev community as to when the same will be
>       available. Incidentally, any news on this effort ? where are we
>       with code, and what's an ETA for a Beta ?
>    4. On the same lines as (3) above, there is a codec dev template in
>       the source tree. Again, where can I find documentation relating
>       to this ? the template has hardly any docs at all.
>
> Best regards and warm wishes for a Merry Christmas and a great New 
> Year to one and all.
The G.729 codec for FS is in testing, and should be out so. If you 
really want to implement your own, TI DSP code is unlikely to be a good 
starting point. I assume that code is fixed point. You really need a 
floating point codec to get any decent speed on a PC. Pentiums and 
Athlons lack saturating arithmetic (MMX actually has partial saturating 
arithmetic, but it isn't much use for anything but image processing), so 
a fixed point implementation ends up very slow.

Steve