IP Telephony, any idea how?

one project i have in mind is to utilize an RPi as a IP telephony set device equipped with a microphone and headset (that is, connected to a VoIP server, or Skype)

any suggestion which distro could be a good choice (capable) for this, and of course application?

[mahjongg]

Biggest hurdle to overcome is that the RPI has no audio in.

You have basically two choices:
Add a USB soundcard, but that means you also have to add a powered hub.

or

patch together a I2S serial sound interface from signals that are available at different points on the R-PI board (I2S isn't officially supported) and write or borrow or otherwise obtain a I2S sound driver for the PI. Connect the I2S bus to a codec chip of your choice and write or borrow or otherwise obtain a driver for that particular chip.

Now you can write or borrow or otherwise obtain the rest of the software you also obviously need.

Biggest hurdle to overcome is that the RPI has no audio in.

You have basically two choices:
Add a USB soundcard, but that means you also have to add a powered hub.

or

patch together a I2S serial sound interface from signals that are available at different points on the R-PI board (I2S isn't officially supported) and write or borrow or otherwise obtain a I2S sound driver for the PI. Connect the I2S bus to a codec chip of your choice and write or borrow or otherwise obtain a driver for that particular chip.

Now you can write or borrow or otherwise obtain the rest of the software you also obviously need.

Thank you. Actually, what I want is just an alternative solution to those PC-based softphone, usually being used by support personnel (helpdesk/service call centers). Instead of having a full-fledged desktop (bulky and with higher power consumption), RPi can be a cheaper option. There's an available USB headset with microphone that can serve the purpose. I am just not so sure if RPi's power can drive this USB headset.

Cheers!

[mahjongg]

probably not as the PI's USB ports are limited to devices that draw less than 100mA, and can work with al limited voltage of just 4.4 Volt, instead of the normal 4.75V. Without an extrernally powered hub you need to resort to a patch know as the PiPass patch which bypasses the USB polyfuses with a 1 ohm or smaller resistor. Its possible, so long as your PSU can deliver the extra power, and there is a suitable driver (recompiled for ARM) for your soundcard.

Assumiing that there is a driver available, I think you could connect a wireless headset via bluetooth.
A usb dongle probably would require less power than a wired headset.