Summary:ASTERISK-03339: ISDN4Linux driven devices only present a lot of noise.
Reporter:unnet (unnet)Labels:
Date Opened:2005-01-24 06:00:18.000-0600Date Closed:2008-01-15 15:23:08.000-0600
Versions:Frequency of
Environment:Attachments:( 0) asterisk.i4l-law.diff
Description:If a call is made where an ISDN4Linux device is in the path it will only generate scatter/gather/noise and misc debris as audio. It seems it has something to do with the removal of the duplicate alaw implementation (chan_modem_i4l.so 1.21)

****** STEPS TO REPRODUCE ******

Upgrade asterisk to CVS-HEAD 24-01-2005 12:23 and call using a ISDN4Linux card. You will hear the noise.


A CVS HEAD checkout from 21-01-2005 00:00 will work correctly.
Comments:By: Mark Spencer (markster) 2005-01-24 07:55:13.000-0600

In which direction does the audio sound bad?

By: Mark Spencer (markster) 2005-01-24 07:58:09.000-0600

Also please try latest CVS (version 1.22) which may fix the problem.

By: unnet (unnet) 2005-01-24 08:08:18.000-0600

It sounds bad in both directions.Version 1.22 of chan_modem_i4l.c does not fix this problem. The sound is so bad that it's total static and nothing else looks like a codec issue.

By: Paul Cadach (pcadach) 2005-01-24 14:09:13.000-0600

Asterisk's A-law and I4L's one have different (reversed) bit order. mu-law looks like have equivalent translation tables. Please, verify attached patch (just move from A-law to mu-law). Thanks.

By: unnet (unnet) 2005-01-24 14:39:02.000-0600

Attached patch works here. I'm now running last CVS (24-01-2005 21:37 CET) with the attached patch and ISDN4Linux works flawlessly.

Audio works on both sides.

By: Paul Cadach (pcadach) 2005-01-24 15:01:08.000-0600

I don't know why A-law and mu-law uses different (reversed) bit orders between Asterisk and ISDN4Linux. Currently, mu-law is the same between Asterisk and I4L, but A-law is reversed at I4L (A-law's "idle" codes is 0x55/0xD5 but for ISDN4Linux this is 0xAA/0xAB respectively).

Moving I4L part to mu-law should fix all compatibility issues between Asterisk and ISDN4Linux parts, what was done by attached patch.

By: Mark Spencer (markster) 2005-01-24 15:41:20.000-0600

Fixed in CVS head, thanks!

By: Russell Bryant (russell) 2005-01-27 18:20:20.000-0600

only an issue in head

By: Digium Subversion (svnbot) 2008-01-15 15:23:07.000-0600

Repository: asterisk
Revision: 4886

U   trunk/channels/chan_modem_i4l.c

r4886 | markster | 2008-01-15 15:23:06 -0600 (Tue, 15 Jan 2008) | 2 lines

Fix chan_modem_i4l to be sure we use unsigned (bug ASTERISK-3339)



By: Digium Subversion (svnbot) 2008-01-15 15:23:08.000-0600

Repository: asterisk
Revision: 4887

U   trunk/channels/chan_modem_i4l.c

r4887 | markster | 2008-01-15 15:23:07 -0600 (Tue, 15 Jan 2008) | 2 lines

Fix law table (i4l) (bug ASTERISK-3339)