- manages multiple unicast and multicast sessions. Thus, there is no need to have several instances of the tool running simultaneously.
- implements RTP, the Real Time Transport Protocol .
- includes a signalling protocol to contact remote parties. For example, use the "Call" button and type person@xxx.inria.fr to get in touch with "person" at INRIA. The signalling protocol also notifies of call acceptance or rejection.
- includes support for sampling rates ranging from 8 to 48 kHz. High sampling rates such as 44 kHz and 48 kHz correspond to CD and DAT quality audio, respectively. Note that different participants in a multicast group might use different sampling rates in a transparent fashion.
- includes a redundancy mechanism for packet reconstruction. The basis for using such a mechanism is described in [1]. The specific mechanism used in Free Phone has been shown to provide much increased audio quality especially when the packet loss rate is high (see [2] and listen to this ). The amount of redundancy included in each packet can be chosen in a manual, semi-automatic, or automatic fashion. In automatic mode, Free Phone automatically selects the amount of redundancy needed to keep the loss rate after reconstruction between some watermarks specified by the user [3].
- supports the redundancy mechanism and the different sampling rates using special RTP payload types .
- includes the usual assortment of codecs, including PCMU, VADPCM (ADPCM-DVI), ADPCM at 6, 5, 4, 3, and 2 bits, GSM, and LPC.
- is compatible with other MBone tools. It is of course compatible with RAT since both were developed within the MERCI project. It is compatible with vat when it does not use the redundancy or the high quality audio features. NeVoT will achieve compatibility with fphone soon.
- uses Tcl/Tk8.0.
New features being added to Free Phone include 3D/spatial rendition of sound, a TCP-friendly rate control, and an "optimal" redundancy control mechanism.
You can subscribe to the fphone mailing list by sending an e-mail to fphone-request@sophia.inria.fr with the subject line `subscribe'.
A screendump of the main Free Phone window is shown below
The main window of Free Phone
If you want to see some other windows of Free Phone, please click here .
