[Asterisk-Dev] Early media in H.323 driver

[Paul Cadach]

Hello,

Chih-Wei Huang wrote:
> Hello all,
> I encountered another problem about H.323 channel driver.
> The scenario is, A calls Asterisk PBX, and then dials B.
> B then sends ringback tone by early media (via faststart or so).
> However, PBX said
>
> chan_h323.c:703 oh323_write: Asked to transmit frame type 4, while
> native formats is 1 (read/write = 1/1)
>
> and hangup the call.

This is because:
1) H.323 allows different codec negotiated for opposite voice path while Asterisk have single codec for channel;
2) There is missed codec negotiation (???, not verified) between OpenH323 stack and Asterisk, so translation couldn't be
set up correctly.
3) Asterisk currently isn't have codec preferences, so it could interfere with 1) and 2).

Usage of translation within oh323_write is complicated because state of the locks is unknown (sometime it calls with
locks held, sometime without ones).

WBR,
Paul.