[asterisk-dev] DAHDI-analog: Unmuting backward audio path when dialing ?

[Martin Harriss]

On 09/12/2012 02:18 AM, Pavel Troller wrote:
> Hi!
>    I'm writing a custom signalling mode for DAHDI analog. One of things, which
> I would like to achieve, is to be able to permanently listen to the channel
> audio even in the dialling (especially pulse mode) state, to hear the dial
> clicks and the cooperating switch responses (in interdigit pauses).
>    I've found, that there is the "dialing" member of the private channel
> structure, which, when set, causes the backward audio path to be blocked.
> It is used for dialing control as well, so it's not possible just to prevent
> it being set.
>    I tried to patch __dahdi_process_putaudio_chunk() in dahdi-base.c driver:
>
>
> static inline void __dahdi_process_putaudio_chunk(struct dahdi_chan *ss, unsigned char *rxb)
> {
>          /* We transmit data from our master channel */
>          /* Called with ss->lock held */
>          struct dahdi_chan *ms = ss->master;
>          /* Linear version of received data */
>          short putlin[DAHDI_CHUNKSIZE],k[DAHDI_CHUNKSIZE];
>          int x,r;
>                          vvvvvvvvvvvvvvvvvvvvvvvvvvvvv
> --->     if (ms->dialing&&  (ms->sig != DAHDI_SIG_UNI)) ms->afterdialingtimer = 50;
>          else if (ms->afterdialingtimer) ms->afterdialingtimer--;
>          if (ms->afterdialingtimer&&  !is_pseudo_chan(ms)) {
>                  /* Be careful since memset is likely a macro */
>                  rxb[0] = DAHDI_LIN2X(0, ms);
>                  memset(&rxb[1], rxb[0], DAHDI_CHUNKSIZE - 1);  /* receive as silence if dialing */
>          }
> ...
>
> where DAHDI_SIG_UNI is my private signalling being implemented. When the
> patch is not there, I'm getting the silent code on the channel (which is
> exactly what the routine is doing). But when it is there, I'm still not
> getting the audio, I'm getting no data instead (the difference is, that
> for example the SIP phone starts to play its own comfort noise because
> it's not getting RTP data).
>
> I'm pretty sure that the hardware and driver can send data even during the
> dialling - when I forcibly clear the dialing variable, I can hear the audio
> including dial clicks etc., but the dialling logic is disturbed and dialing
> stops after the first digit is sent.
>
> I'm unable to find another place, which probably either stops reading audio
> from the channel or stops bridging them to the originating channel - I
> scanned chan_dahdi.c, sig_analog.c and physical DAHDI card driver, but
> to no avail.
>
> With regards,
>    Pavel
>
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Pavel,

You might also like to look at this page:

http://octothorpe.info/site/asterisk-cnet

The patches there are for use by those of us who like to interface 
asterisk to antique electromechanical switches.  I'm curious to know 
what your application is!

Martin