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Does Anyone Know about Internet Telephony?

I am curious about VOIP from a developer's perspective.


I would like to implement a 'solution' that allows incoming messages or faxes to be taken at an assigned phone number and stored on my own internet-connected server. Likewise I would like the capability to call out from an internet connected server, from a program, to real world phone numbers  - for instance, to distribute messages to an organization's membership.


So what I'm thinking of is basically a sort of specialized virtual PBX with fax and automated outbound capabilities.


Now, is there a commercial service that sells access to an "access point" (for want of a better word) that would allow an internet connected computer to access "real" physical real world phone lines? Ideally, I'd rent minutes and I'd rent access to a dedicated phone number. The inbound and outbound audio data streams would be socket IO to my server.

I know that my question probably scratches the surface of a vast sea of knowledge. Please be kind.... I don't even know where to begin researching this stuff.

Thanks.

Tele-Phony Guy
Tuesday, March 04, 2003

Oh, yeah... I am interested in this from a DEVELOPER'S perspective. I know that there are several virtual PBX and internet based message services for consumers and end users that make the user go through a bundled software package to monitor calls or download messages. I can't use this level of service for what I'm planning.

I want something that allows me to write my own software for this purpose - for instance, allowing me to capture inbound voice messages to WAV files and then doing something with them based upon caller ID, as an example.

Tele-Phony Guy
Tuesday, March 04, 2003

I don't know much about it, but this sounds interesting, ....

If you do find something could you pls email the links/ etc to me.

Thanks,

Prakash S
Tuesday, March 04, 2003

Alcatel OmniPCX 4400

Dino
Tuesday, March 04, 2003

"Does Anyone Know about Internet Telephony?"

I know it sucks.

Glad to be of help!

TJ Haeser
Tuesday, March 04, 2003

Have a look at the YAC Number section on http://www.yac.com

This (free to subscribe) service allows phone redirection voicemail and faxing.

Also http://www.MediaRing.com.

Try searching google for "softphone".

Justin
Tuesday, March 04, 2003

A bookstore should have a small but
respectiable telephony section in the
technology and computers section check it
out. Unfortunately the telcom industry find
it necessary to come up with trillions of
bizarre acrynums and concepts and much of
that made it into the internet telephony
world. A big picture book will help prep you
a lot. After that you might want to try an
API book like JTAPI (Java) or a collection
of system tools like Bayonne For Linux
(C/C++). Good luck :)

Li-fan Chen
Tuesday, March 04, 2003

There used to be a magazine call "Computer Telephony", but business is down so they renamed it to some portal-sounding name like "A Magazine About Any Modern Devices that uses electricity"...
They have a website, check them out. You might find some of those telephone access point you are talking about.

Another thing: Microsoft has TAPI 3.0, it's like Java's JTAPI, but in COM. John Wiley Publishing attemptd to write an open source visual basic wrapper around TAPI 2.0 I think, check that out.

Li-fan Chen
Tuesday, March 04, 2003

Session Initiation Protocol (SIP) is a good place to start, although SIP is in it's infancy and supports a lot more than just VoIP. Check out http://www.sipcenter.com for more info.  Another good resource is 2600, the hacker quarterly. They have lots of info, descriptions, and some details on switched networks, LATA's, etc. which may or may not be helpful to you. Pick it up your local bookstore or magazine rack if you can find it. It's on the web at http://www.2600.com

-j
Tuesday, March 04, 2003

It sounds like you don't want to host the actual hardware. You might want to look into Voxeo for something like this. Take a look at www.voxeo.com.



jerry
Tuesday, March 04, 2003

Check out Vovida's VOCAL system. This is a complete library of SIP-based VoIP and call processing functionality.

http://www.vovida.org/

Larry
Tuesday, March 04, 2003

Everyone - THANKS. The links that  have been provided look great.

I just needed a starting point so I could come up to speed on the terminology.

The question/statement about not wanting to host the phone access myself is correct. I only want to host a network server  (IE, pure software) and I want to outsource the physical access to the telco lines.

Tele-Phony Guy
Tuesday, March 04, 2003

H323 is the big standard for VoIP. There is also SIP which is simpler.  The vovida stuff is open source.
Cisco has their own form of simplified H323 called Skinny. They also make POTS to IP gateways. Get out your checkbook.
Avaya, Nortel and all of the bigger networking hardware companies are investing in VoIP.

Doug Withau
Tuesday, March 04, 2003

Hi,

I understand exactly what you want, but am not sure if such a hosted solution currently exists. The effort of sending a bit stream to a server that would make calls is a piece of cake actually and you don't necessarily need VoIP to accomplish it. All you need is a server that can encode (transcode actually) your packets into a G.711 stream that is passed to the PSTN (public switched telephone network). The G.711 codec is only necessary if you want to fax stuff or want to ensure compatibility. There are cards that can do this, but I'm not aware of a hosted service that provides what you're looking for.

The card itself would probably have an Ethernet interface (or through a NIC via the PCI bus) and break up the voice packets into a series of bits that would be reformed (probably through FPGAs or DSPs) into a normal TDM (time division multiplexed) voice channel called a DS0 (digital signal 0, the lowest bit rate channel in the telephone network). The card may have a normal telephone jack on it but more likely has a T1 coming out of it (if they have more than one customer :-).

The encoding of the bits into the DS0 is handled by a software codec. The ITU maintains standards for these codecs, but the G.711 codec is the most used and most compatible one (and the only one available for faxes). It offers a 64Kbps bit rate (8 bit samples at 8KHz).

Now, as to what format to send your packets in, that's the question. If you use a VoIP protocol, it would probably be an RTP/UDP stream with SIP and/or H.323 to control it. There is a hodgepodge (i.e., mess) of protocols out there now, but you would ultimately have to use whatever the host provider would want anyhow. Try Googling on "hosted telephony provider soft VoIP fax call support" or stuff like that.

Email me at anytime. If I'm free, I'll help you out. voip@axebow.com

Battered VoIP Expert
Tuesday, March 04, 2003

Oh, and one more thing. If you could get a host to accept WAV files, then it wouldn't really be VoIP at all. IMHO, an MP3 format would be much better and I'll bet that someone is working on an MP3 to voice call converter somewhere right now (Cf. IVR systems). A lot of embedded products that use voice are looking at the MP3 format right now becuase it's free, relatively easy to implement, and inherently has variable characteristics.

BTW, a "VoIP" call would entail you running some sort of *real-time* encoder on your PC that would take an analog source or waveform input and transmit it immediately to a far end with all of the performance handling characteristics that real-time stuff demands. If your connection wasn't up to snuff, packets would drop left and right and quality would suffer.

Battered VoIP Expert
Tuesday, March 04, 2003

"Does Anyone Know about Internet Telephony?"

Sure, someone does.

www.catb.org/~esr/faqs/smart-questions.html


Wednesday, March 05, 2003

Not sure what platform you are developing for, but inside the Microsoft Platform SDK there are some TAPI examples for TAPI 3 (The COM Implementation) and for TAPI 2. 
The TAPI 3 samples work with streaming files and recording conversations and stuff like that.  You might be able to find what you are looking for there.

They helped me out in my current TAPI fiasco.

Matt Watson
Wednesday, March 05, 2003

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