RAT v4.0.0 release
RAT v4.0.0 was released on 31 March 1999 (changelog). This was a major release, adding support for multiple audio sampling rates and sample rate conversion, spatial localisation, improved packet loss concealment, and a message bus for inter-component and inter-application communication.
The announcement from the original release follows:
We are pleased to announce the release of RAT v4.0.0.
RAT is the premier open source voice-over-IP application. It allows users to participate in audio conferences over the internet. These can be between two participants directly, or between a group of participants on a common multicast group. No special features are required to use RAT in point-to-point mode, but to use the multiparty conferencing facilities of RAT, all participants must reside on a portion of the Internet which supports IP multicast. RAT is based on IETF standards, using RTP above UDP/IP as its transport protocol, and conforming to the RTP profile for audio and video conference with minimal control.
RAT features sender based loss mitigation mechanisms and receiver based audio repair techniques to compensate for packet loss, and load adaption in response to host performance. It runs on a range of platforms: FreeBSD, HP-UX, IRIX, Linux, NetBSD, Solaris, SunOS, and Windows 95/NT. The source code is publicly available for porting to other platforms and for modification by others.
Note that RAT does not perform call services like user location, neither does it listen to session announcements to discover advertised multicast sessions. For these purposes, it is recommended you use RAT in conjunction with the Session Directory (SDR), or a similar application.
This experimental release offers a number of new features compared to the stable release but has had considerably less testing. The additional features include:
- Improved audio quality.
- Support for multiple sample formats (sampling rates of 8,16,32,48 kHz and mono and stereo).
- Sample format conversion.
- Additional codecs: Wide Band ADPCM Speech Codec (16kHz, 64 kbps), G726-3/4/5, VDVI.
- Sound localization (3D positioning of audio sources).
- Improved Automatic Gain Control.
- Improved user interface.
- Separation of audio engine and user interface components.
- Conference bus for inter-component and inter-application communication.
- Lip synchronization via the conference bus.
- Support for interleaving to mitigate packet losses.
- Improved Windows audio support (mixer control and format conversions).
- Balloon help to explain all options.
- Reception quality matrix.
The release includes source code only -- binaries are not available at this time. We also provide anonymous CVS access to our source code for those wishing to use the most up-to-date sources, and encourage the submission of patches.
Colin Perkins/Orion Hodson
Networked Multimedia Group
University College London