[Asterisk-Users] feature - VM gain adjust?

[John Todd]

At 5:00 PM -0600 on 7/11/04, Rich Adamson wrote:
>I'm toying with adding a feature request to provide some sort of
>gain setting for voicemail when accessed from "certain" interfaces.
>Maybe something like voicemail=6.0 (db) within a specific channel
>section of zapata.conf corresponding to a pstn line.
>
>Situation:
>1. Someone calls into asterisk and leaves a voicemail. The sound
>is recorded at some volume well below 0 db, and is directly related
>to the distance asterisk is from the central office (pstn cable
>loss) plus whatever distance the user placing the call is from
>his/her central office.
>2. I receive a text message that a voicemail was left.
>3. I call into asterisk remotely (assume from a cell phone) and
>retreive the voicemail. My location creates another xx db of loss
>between myself and asterisk, and voicemail can hardly be heard.
>
>Actual Measured Values:
>1. Asterisk is 5.6 db from the central office. Called from one
>pstn line, through the central office, to asterisk and sending a
>1004 hz tone at 0db. Recorded the tone into voicemail. (Tone should
>have been recorded at about 11.2db, two times the cable loss)
>2. Called into asterisk again, this time to retreive the voicemail
>and measured the 1004 hz tone from voicemail. It was -36db "actual".
>This retreival added another 11.2db of loss due to pstn interfaces
>and plant loss.
>3. The calls were through a TDM FXO module with rx and tx gains
>set to 0. (Changing rx and tx gain to +3 db and repeating the test
>resulted in a measured -30.5db signal, but these settings create
>unwanted echo issues. Therefore adjusting channel gain is not an
>option.)
>
>The end result is that retreiving any voicemail message left from
>a distant location and retreived from a distant location can hardly
>be heard. By adding the proposed voicemail=6.0 statement to the
>appropriate channel, any calls connected to voicemail via that
>channel would effectively increase transmission levels by 6db (or
>whatever the setting happened to be). In this example case, the
>setting would increase the vm volume by 12db (or about 24db measured
>in the above).
>
>Anyone have any thoughts on this?
>
>Rich

Rich -
   I'll say that this would be very useful.  Regardless of where the 
loss is being inserted, it still exists.

   I like the idea of associating the voicemail db adjustment on a 
per-channel basis.  I don't want to have to dink around with yelling 
at the telco to fix something that "just works" otherwise.  Their 
answer will be "Well, turn up the volume on your phone!" which is 
exactly what your proposed patch will do.  A simple trial-and-error 
process should be able to sort out the proper adjustment on any 
typical system that doesn't have radical db changes across time.  I'm 
heartily in favor of this idea; I'll even throw a donation towards 
it, if you have a PayPal account.

   Another cool feature would be app_volume, which would turn up/turn 
down tx/rx levels dynamically, but that's left for a different day, 
and after we have an enhanced app_dial that lets single-digit dtmf 
sequences jump to dialplan routines and then can reconnect bridged 
calls.  See my various rantings about this in months (years!) past. 
When I get some spare time (ha ha ha) I should really learn how to 
code this stuff...

JT