[Asterisk-Users] zaptel: [rx|tx]gain on E1/PRI/isdn audio quality problems

[Lele Forzani]

Hello,
i'm using a TE410P on some E1/PRI with EuroISDN and experiencing a few audio 
quality problems with current CVS (both zaptel and asterisk) and the 
following network

ISDN public                                                   SIP/zaptel
network ---- pri --- ASTERISK GW --- iax --- ASTERISK PBX --- PHONES
                                 w/ any codec


the rx (public network to local phone) audio channel is audibly too loud and 
peaks are clipped as if something in the path is increasing the level of 
about 3dB on both SIP and zaptel phones.
Prompts on ASTERISK GW are unaffected, only audio coming from the PRI is 
distorted. Also, ASTERISK PBX has a chan_capi device, which has good audio as 
well.

Setting 'rxgain=-3.0' on the ASTERISK GW fixes the problem[1] but it looks to 
me there must be something wrong if alaw digital voice coming from the ISDN 
network is clipped when going through an iax channel.

thanks,
lele


[1] incidentally, when trying to fix this problem I discovered that _at least 
in my setup_ chan_zap is not correctly setting the rxgain/txgain for outgoing 
calls. I nedeed to add a call to set_actual_gain() in zt_call().

--- chan_zap.c  14 Oct 2003 09:56:46 -0000      1.111
+++ chan_zap.c  17 Oct 2003 23:29:31 -0000
@@ -1305,6 +1311,8 @@
        if (res)
                ast_log(LOG_WARNING, "Unable to flush input on channel %d\n", 
p->channel);
        p->outgoing = 1;
+
+       set_actual_gain(p->subs[SUB_REAL].zfd, 0, p->rxgain, p->txgain, 
p->law);

        switch(p->sig) {
        case SIG_FXOLS: