Subject: Re: [linux-audio-dev] Amateur Radio Repeater - Audio control via soundcard
From: Jörn Nettingsmeier (nettings_AT_folkwang-hochschule.de)
Date: Tue Apr 10 2001 - 19:39:59 EEST
"Howard, Chris" wrote:
>
> Hi,
>
> I am not subscribed to this list, but I have a quick
> question if you all will indulge me.
>
> I am looking at building an amateur radio repeater for use
> in my area. And since I am a software guy, I thought I would
> approach it from a software perspective. I am investigating using
> a soundcard in a Linux machine to do the job.
>
> A repeater is a radio system where the input and the output
> are on different frequencies. The receiver is set up with
> a squelch, and it's output audio is sent to the transmitter
> via a control circuit. The control circuit senses activity and
> keys up the transmitter and sends it the audio for output.
> There are also other tasks the controller can do, like injecting
> some audio of it's own for station identification, handling timers
> to limit long conversations, and detecting DTMF tones and subaudible
> tones on the input for doing control functions like shutting the thing
> off.
>
> I have read the information about full duplex and low latency. I think
> those things are within my ability. The part I am particularly stumped
> about is tone detection. This is not a signal modification DSP kind of
> effort, just detecting whether a particular tone pair (DTMF) or subaudible
> tone is part of the audio input.
>
> I would appreciate any leads or advice you all might have for me.
you should check out the music-dsp mailing list.
find it at http://shoko.calarts.edu/musicdsp/.
it's not linux-specific, but if i understand you correctly, your
problem boils down to some fft analysis, which is a frequently
discussed topic there, so check the archive.
at the site, you will also find a source code repository - perhaps
there is a good solution to your problem there ?
regards,
jörn
-- Jörn Nettingsmeier home://Kurfürstenstr.49.45138.Essen.Germany phone://+49.201.491621 http://www.folkwang-hochschule.de/~nettings/ http://www.linuxdj.com/audio/lad/
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