On 02/09/2011 12:09 AM, Steven Ayre wrote:
> Annex A is just an alternative way of encoding the data, using less
> processing power but at poorer quality. They generate compatible data
> - decoders both with and without annex a support decode both G729 and
> G729A encoded data. The difference is purely in the implementation of
> the encoder/decoder. If your device uses G729A in the SDP, it's broken.

This is correct, but there are still quite a few things around that have
broken SDP that says g729a. The last time I looked, Freeswitch had a
fudge in the source code to tolerate that.

>
> Annex B uses the same PT & name. It does work in passthrough mode, as
> does plain G729.

There is supplementary info in the SDP to say whether AnnexB is enabled,
like so:

a=fmtp:18 annexb=yes

> -Steve
>
>
> On 8 February 2011 15:31, curriegrad2004 <curriegrad2004@gmail.com

> <mailto:curriegrad2004@gmail.com>> wrote:
>
>     G729 only. No A's or AB.
>
>     If you want to pass through other variants of G.729, you can simply
>     modify mod_g729.c to include additional variants of G729
>
>     Which by the way, I've pasted the area of the code you might want to
>     modify. I've done this on mine and it worked fine as pass through.
>
>     00217         SWITCH_ADD_CODEC(codec_interface, "G.729A");
>     00218         for (count = 12; count > 0; count--) {
>     00219                 switch_core_codec_add_implementation(pool,
>     codec_interface,
>     00220
>                            SWITCH_CODEC_TYPE_AUDIO, 18, "G729A", NULL,
>     8000, 8000, 8000,
>     00221
>                            mpf * count, spf * count, bpf * count, ebpf *
>     count, 1, count * 10,
>     00222
>                            switch_g729_init, switch_g729_encode,
>     switch_g729_decode, switch_g729_destroy);
>     00223         }
>
>
>     On Tue, Feb 8, 2011 at 7:02 AM, Sam <u2nsam@gmail.com

>     <mailto:u2nsam@gmail.com>> wrote:
>     > Hi,
>     >
>     > Which type of  G.729 codec does freeswitch uses in passthrough
>     mode ?
>     > Is it g729a or g729b or g729ab .
>     >
>     > Regards
>     > Sam
>

Steve

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