Summary:ASTERISK-04538: Capi
Reporter:Marco Löwl (mloewl)Labels:
Date Opened:2005-07-08 03:44:39Date Closed:2011-06-07 14:02:52
Versions:Frequency of
Environment:Attachments:( 0) CxEcho.pdf
Description:there are two general issues with Asterisk at a first glance:
- the tiny issue is that facility selector 6 is used to switch on the
echo canceller. Facility selector 8 should be used instead. In our
procucts we implemented the LEC as facility selector 6 first, but the
CAPI association approved 8 because the 6 was allocated by the CAPI
Broadband Extension. We adapted it meanwhile.

- it seems that Asterisk doesn't make use of the delivery confirmation
for transparent data (see DATA_B3_REQ, delivery confirmation flag). This
delivery confirmation is a way to control the queue size for outgoing
data and thus to keep a short delay on a connection. For links between
ISDN cards this is no issue since they all follow the ISDN clock. But as
soon as data from another clock source is involved the ISDN card would
buffer data and cause long delays. The delivery confirmation bit just
causes the DATA_B3_CONF to be indicated when the last byte of the data
block has been sent to the line. The queue size then corresponds to the
DATA_B3_REQ's pending at that moment.
Comments:By: Marco Löwl (mloewl) 2005-07-08 03:49:12

0:00:36.827 CAPI20_PUT(021)
 0x0000  01 00 80 80  3D 04 01 04  07 00 06 00  06 01 00 02  ....=...........
 0x0010  00 40 00                                            .@.
 FACILITY REQ             AppID 0x0001 MsgNr 0x043d NCCI: 0x00070401
   Facility selector: 0x6 Broadband Extensions/Echo Cancellation
   Facility parameter (0x6):
     Function: Enable line echo canceller operation
     Echo Canceller parameter (0x2):

By: Michael Jerris (mikej) 2005-07-08 09:09:44

Can you provide a patch for either of these issues?

By: Russell Bryant (russell) 2005-07-08 09:22:58

chan_capi is not a part of Asterisk.  Please submit any issues you have with it to their developers.  Here is the project web page.