Subject: From: Date:

Re: [ECS] Telephony Dario Greggio Tue, 28 Nov 2000 11:20:08 +0100

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> "Richard V.C. Tinker" wrote:

Just want to spot a few things:

> 1. Mark's idea of passing the audio to/from the voice modem and the
> sound board is exactly what the current released version of HAL2000
> does today.  The problems with it are too numerous to list, but here
> are some of the top ones:  A. Audio quality typically sucks.  B. Some
> sound boards cannot be modified for unamplified (e.g. line level)
> output, which is what you need in order to be able to connect it to
> the mic input of the voice modem, and THEN you need an stereo audio
> connector "Y" adapter and amplified speakers to hear anything out of
> the sound board.  Conversations over the telephone will be heard over
> the speaker as well unless the software manages communicating with the
> sound board's software mixer (and they are not all compatible with the
> Microsoft provided interface to the mixer) so that the LINE IN or
> whatever is used to accept the audio from the voice modem can be muted
> when not in use.

I agree that interfacing the telephone line to an audio board is not
easy, but it *can* be done: I was thinking about a small device to be
connected to an external port (just not to steal one more slot, ISA or
PCI) with a few relays, maybe a 8870 chip to recognize DTMF (it could be
done by sampling and FFTing software, but the chip would be easier), and
audio amplifiers/adapters and transformers.
I guess that, if needed, you could use two audio boards (they're cheap)
and two PCI or a PCI and an ISA should get into no conflict.
You're right about troubles in handling the mixer from Microsoft's APIs,
but it happened to me only once out of 5 or more boards.

Of course, TAPI is far easier and usually good enough, even if...
 
> 2. Good quality audio comes from getting it directly from the data bus
> of the modem - e.g. WAV audio direct from the voice modem.  Contrary
> to popular belief, that does not automatically mean TAPI.  You can
> send/receive WAV audio with the voice modem using standard AT
> commands.  If the programmer is especially sharp (let's see if Mark
> can take the bait on that one) then it can be done in full-duplex mode
> with many of today's modems.

I'm getting Caller ID (only from ISDN), fax class 1 send/receive, data
mode (seldom used), DTMF with very *few* errors, audio quality so-so
(you may try to listen MP3s played at +39/011/336768 !).
As far as I know, I'm sure you can never have real time full-duplex with
TAPI WAV interface or AT commands. It's simply not fast enough, it was
meant for one-way sending/receiving and the modem has no buffer
(usually) to sample what he's hearing while it's talking.
I'd be very glad if anybody would show I'm wrong! I'd love that feature!
At the moment I'm barely getting real-time remote audio monitoring: I
sample 1sec bunches from the MICs, using the audio-board, and then play
them into the modem.
 
> 3. Extensibility, or in layman's terms the ability to modify the

Of course! Anybody knows more about JTAPI?

> 4. Limitations of TAPI were a big pain in the butt.  One of them was
> that with HAL2000, you can pick up any phone in the house, press #,
> and then talk to HAL.  We could find modems that still had the local
> handset on-hook/off-hook detection circuitry on them (although it was
> hard), 

I'm using TAPI 2.0. Anyway, I'm not using modem-recognized telephone
going on and off-hook. I simply put a small relay through the telephone
cable, and it tells the software somebody picked it up.

-- 
Ciao,
Dario
--
ADPM Synthesis sas - Torino
--
http://www.geocities.com/adpm99

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