Re: [Flightgear-devel] ATC voice howto
Martin Spott wrote: When you take the 'philosophical' route, I agree - in almost _every_ situation it's a big fault to delete detail/resolution from your raw data. On the other hand: 8 kHz, 8 bit is not that bad. German ISDN telephony has this resolution and to my impression the audible quality is far better than usual radio in an aircraft ;-) ISDN uses the uLaw compression which means, compress 16-bit audio into 8-bit by removing less relevant bits as the audio gets louder. Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] ATC voice howto
Erik Hofman [EMAIL PROTECTED] wrote: Martin Spott wrote: On the other hand: 8 kHz, 8 bit is not that bad. German ISDN telephony has this resolution and to my impression the audible quality is far better than usual radio in an aircraft ;-) ISDN uses the uLaw compression which means, compress 16-bit audio into 8-bit by removing less relevant bits as the audio gets louder. Oh, sorry, I didn't expect the system to be _that_ sophisticated ;-) Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] ATC voice howto
Jonathan Richards wrote: On Thursday 12 Feb 2004 5:31 pm, David Luff wrote: OK, here's some instructions on how to generate new ATC voices for FlightGear. Hopefully this will make some sense to somebody, ask if it's unclear. snip Two files are required for each voice - a wave file containing the actual sounds, and an index file that basically describes where in the wave file buffer to find each word or phrase. The current voices for the ATIS can be found in $FG_ROOT/data/ATC and are called default.wav and default.vce for the wave and index file respectively. Note that one important change will be made in default.vce - currently it is indexed by byte position into the sound buffer, but I've decided it would be better to index by time into the buffer, since that is more robust to changing the recording quality, and in the future possiby using encoding such as Ogg Vorbis. Also, the first line currently contains the number of subsequent lines, but I think that can be ditched! massive snip David In what units shall the time index be specified? The sampling rate sets a resolution limit on the timing, so for 8kHz we only need 1/8000 sec = 125 microseconds precision, but if we have an ambition for higher rates, we need more. [1] In reality, radio comms are not HiFi standard. Does anyone know what the typical bandwidth is? Or should we simulate by taking a beautiful 22kHz recording and filtering it to sound like the real thing? Perhaps as an option, so one can do radio practice with bell-like clarity at first, and graduate to crackly reception of foreign languages and accents later! Regards Jonathan [1] It occurs to me that for chunked formats like WAV, there is a mathematical relationship between the byte position and the time offset which could be used for conversion, no? Does anyone know, does Plib include realtime sound mixing, downsampling and volume control (the sound should be downsampled to match the real aircraft comms, it should be more soft when you're further away from the transmitter and we should mix some noise sounds with a speech to sound everything more like in real life). - Matevz ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] ATC voice howto
snip Anyone got any wavefile editor recommendations BTW? I used CoolEdit (Windows) for the ATIS, but the trial period is now long gone, and when I went to buy it I found the guy had sold it to Adobe and the price had tripled. No thanks! I'm using Audacity now, but it's not entirely polished, and the sound is not in sync with cursor movement when playing a small selection in recent versions. Crucial factors are the ability to extend or contract a selection by either edge, and easy copy and pasting into a new buffer, plus display of time or byte position. There's loads for Linux, but I haven't found a really likeable one yet, Audacity being the nearest so far. Cheers - Dave I use WaveFlow (http://www.waveflow.com). Good interface, copes with massive (30 minute+) recordings reasonably fast, and is under active development. Richard ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] ATC voice howto
On Thursday 12 Feb 2004 5:31 pm, David Luff wrote: OK, here's some instructions on how to generate new ATC voices for FlightGear. Hopefully this will make some sense to somebody, ask if it's unclear. snip Two files are required for each voice - a wave file containing the actual sounds, and an index file that basically describes where in the wave file buffer to find each word or phrase. The current voices for the ATIS can be found in $FG_ROOT/data/ATC and are called default.wav and default.vce for the wave and index file respectively. Note that one important change will be made in default.vce - currently it is indexed by byte position into the sound buffer, but I've decided it would be better to index by time into the buffer, since that is more robust to changing the recording quality, and in the future possiby using encoding such as Ogg Vorbis. Also, the first line currently contains the number of subsequent lines, but I think that can be ditched! massive snip David In what units shall the time index be specified? The sampling rate sets a resolution limit on the timing, so for 8kHz we only need 1/8000 sec = 125 microseconds precision, but if we have an ambition for higher rates, we need more. [1] In reality, radio comms are not HiFi standard. Does anyone know what the typical bandwidth is? Or should we simulate by taking a beautiful 22kHz recording and filtering it to sound like the real thing? Perhaps as an option, so one can do radio practice with bell-like clarity at first, and graduate to crackly reception of foreign languages and accents later! Regards Jonathan [1] It occurs to me that for chunked formats like WAV, there is a mathematical relationship between the byte position and the time offset which could be used for conversion, no? ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] ATC voice howto
Jonathan Richards writes: In what units shall the time index be specified? The sampling rate sets a resolution limit on the timing, so for 8kHz we only need 1/8000 sec = 125 microseconds precision, but if we have an ambition for higher rates, we need more. [1] In reality, radio comms are not HiFi standard. Does anyone know what the typical bandwidth is? Or should we simulate by taking a beautiful 22kHz recording and filtering it to sound like the real thing? Perhaps as an option, so one can do radio practice with bell-like clarity at first, and graduate to crackly reception of foreign languages and accents later! Regards Jonathan [1] It occurs to me that for chunked formats like WAV, there is a mathematical relationship between the byte position and the time offset which could be used for conversion, no? Fantastic, a post not talking about rotating planes on their noses ;-)) Time index should be specified in seconds I think. Yes there'll be a lot of decimal points, but it's SI, and it's typically what wavefile editors natively display. In practice it probably doesn't matter if the time resolution spans a few bytes, especially at higher rates, since there's generally a slight gap between words, and if there isn't it's a good candidate for a run-together phrase. I guess comms aren't always that clear in real life, but at least if recordings are made at good quality to start with its optional whether to degrade them or not. At present the 8,8 limitation forces some degradation, and I'm not sure if the sort of 'muffled' quality that it imparts is what we're after. Yes, there is a relationship between byte position and time for wave files, which is how I'm going to convert the current default.vce. I think time is the best way forward though ever since someone mentioned Ogg Vorbis at one point. Plus I think Audacity only displays time, not byte position. As I say, I'm not an audio guy, so I'm open to being persuaded that another way is better... Another thing, some folk running Linux (David Megginson and at least one other) have reported only being able to hear the ATIS extremely faintly in the past. I'm not sure why, but it might be best *not* to copy the volume characteristics of default.wav, but to do what you think is best and see how it goes. Anyone got any wavefile editor recommendations BTW? I used CoolEdit (Windows) for the ATIS, but the trial period is now long gone, and when I went to buy it I found the guy had sold it to Adobe and the price had tripled. No thanks! I'm using Audacity now, but it's not entirely polished, and the sound is not in sync with cursor movement when playing a small selection in recent versions. Crucial factors are the ability to extend or contract a selection by either edge, and easy copy and pasting into a new buffer, plus display of time or byte position. There's loads for Linux, but I haven't found a really likeable one yet, Audacity being the nearest so far. Cheers - Dave ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] ATC voice howto
On Thu, 12 Feb 2004 21:05:25 +, David Luff [EMAIL PROTECTED] wrote: Anyone got any wavefile editor recommendations BTW? I like GoldWave. www.goldwave.com I used CoolEdit (Windows) for the ATIS, but the trial period is now long gone, and when I went to buy it I found the guy had sold it to Adobe and the price had tripled. No thanks! I'm using Audacity now, but it's not entirely polished, and the sound is not in sync with cursor movement when playing a small selection in recent versions. Crucial factors are the ability to extend or contract a selection by either edge, and easy copy and pasting into a new buffer, plus display of time or byte position. You can chose to display time or sample position, but the time display has only 3 decimal numbers. -- Roy Vegard Ovesen ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
