> I'd be very happy to hear your opinion on VATSIM, as I've ben trying to > push the idea of human voic ATC within FlightGear. I _do_ have some > ideas how voice ATC could/should be realized but my ideas didn't fall > on prolific soil,
OK, here's the breakdown. I've used VATSIM with FS2004+FSInn and X-Plane+XSquawkBox. Most importantly, make sure there is no text mode. On VATSIM, you can go online either using text or using voice, which means that there are users who are not aware of any voice transmissions, and also that voice users are required to read text transmissions (which is a bit much to expect on a manual short final, for instance). Last night, in particular, I was faced with the situation that a text-only jet airliner popped up in front of me from below while I was 4nm final or so -- he had no idea that I had been cleared to land on the voice channel, and ATC had probably forgotten that my Dash7 was a lot slower than the jet. This also means that UNICOM must be voice, not text-only as on VATSIM. This is most easily accomplished by creating unmanned idle ATC posts on given frequencies across the globe, running on the ATC server(s). On VATSIM, pushing PTT does NOT disable radio reception on that radio, which is unrealistic. Make sure PTT turns the corresponding COM audio output off. On the issue of realistic distortions -- can anyone tell me what modulation air communication uses? Latency on the voice channel is not a problem, since radio communication is always PTT-based. So I would go for the simplest option of using the speex codec and a simple TCP-based protocol (maybe using the streaming parts from IAX2?). Just make sure it traverses NAT routers transparently! And I don't think P2P connections are required -- all voice had better go through the servers. Which brings me to another problem -- the VATSIM ATC client needs open UDP ports on any firewall/router that separate it from the internet. This is bad as it requires reconfiguration of existing network installations, so I think it's important to make sure everything traverses NAT and firewalls transparently. On VATSIM, there is a general bad habit of not checking ATIS. This is probably because ATC are not really forced to issue ATIS, and there is usually no voice ATIS (I think it must be recorded manually). Since FlightGear already has code for voice ATIS, it should be possible to create voice ATIS on all published ATIS frequencies. This can (should -- as part of the ATC logon procedure) be set by the responsible ATC, and in its absence the current METAR can/should be relayed. The latter is required because otherwise you have no good way of working out QNH/base pressure for an unmanned airport. The last issue (though not very important) is visualization. Though not a voice issue, it would have to be dealt with as part of the system sooner or later. VATSIM pilot clients, to the best of my knowledge, only send information on the position and attitude of the aircraft, along with rates of change. It wouldn't be very hard to include second derivatives (accelerations), which would, for instance, make take-off and landing rolls look much smoother in case of network load problems (I have seen aircraft on landing roll jumping back by several 100ft on VATSIM...). I also don't like the way aircraft visual models are dealt with in VATSIM: only a code describing the aircraft type is transmitted, leaving the client software to find a suitable model. I'm very much leaning towards each client submitting the rough geometry of the airframe, including reference point, to the ATC servers so that other clients can download and show them (this would only have to be done at logon time and can be asynchronous, so I don't expect bandwidth problems). Only the copyright issues would have to clarified. As a suggestion, for copyright-protected airframes, one could transmit a few main points on the airframe only so that the other users can anticipate the extent of the aircraft without seeing its exact shape. What do you think? Andras ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
