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?
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