Le 24/03/2017 à 23:01, Matt Fredrickson a écrit :
On Fri, Mar 24, 2017 at 7:43 AM, Jean Aunis <[email protected]> wrote:
Hello,
I need to add support for a new audio format in Asterisk. It will be
actually a very limited support : I just need to take the audio from one
side and transmit it to the other side. No decoding / transcoding will be
involved. One side will be a DAHDI endpoint, the other one a SIP endpoint.
What's the new audio format, if you don't mind me asking? (/me wonders
if it's CLEARMODE)
As far as I know it will be a home-made codec which I know nothing
about. But it's a good thing you mentioned CLEARMODE : I had not heard
about it before, but it seems perfectly fit for what I'm trying to achieve.
So maybe I will implement this by adding support for CLEARMODE.
Let's put aside for the moment the modifications which may have to be done
on the channels drivers to handle the codec negotiation. If I focus on
Asterisk's core and RTP handling, it seems I could achieve this simply by
registering a new format in codec_builtin.c. Two questions then :
- firstly, is this really the only thing to do, or am I missing something ?
I forget every time I've had to do this, and end up relearning it
every time. Here are some other places that you'll need to modify:
main/rtp_engine.c: Some work here to work with SDP based protocols, like SIP.
include/asterisk/format_cache.h: To declare the new format in a header file.
main/format_cache.c: Also need to define the format here.
channels/chan_dahdi.c: It needs modified for support for any new
codecs that it needs to work with.
Thank you for these points. I originally thought that adding a new line
"CODEC_REGISTER_AND_CACHE" would magically do everything required, but
now I see there is some more work to do. Still, it seems to remain quite
easy.
- secondly, is there a more "pluggable" way to do this ? Maybe with a shared
object which would be loaded on startup ?
Good question. I don't think that there's a great way to add a
completely new codec (not previously described in Asterisk at all)
without patching Asterisk. Perhaps Josh Colp or Kevin Harwell can
correct me if I'm wrong :-)
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