[fpc-pascal] Modems etc.

Lukasz Sokol el.es.cr at gmail.com
Tue Jul 21 10:01:27 CEST 2015

On 20/07/15 17:32, Mark Morgan Lloyd wrote:
> Lukasz Sokol wrote:
>> It's been years since I had anything to do with DSP, unfortunately,
>> but with the FFT running on the sliding 26-sample-long window, and
>> a /reverse/ FFT to produce the 26-long sample from just having a
>> byte or 2 written to an array, the kind of SIMD processing probably
>> won't be very time consuming... and, operating on a fixed size
>> array, would be of fixed-processing-time, which is usually handy.
> Thanks, noted. I must admit that I've never dabbled directly with
> FFT, but perhaps now is the time to start. I need to do a couple of
> test simulations first to demonstrate that working in the frequency
> domain is more promising than the time domain (I'm having to fight
> off the boss's suggestion that I simply time zero crossings).
>> Just my £0.02p :) el es
> Worth more than you think
> http://www.bbc.co.uk/news/uk-england-berkshire-33586245 :-)
Thinking about it some more, it could actually be true that FFT/DFT is overkill.

For detection you need 4 specialized discrete band-pass (1 freq pass) filters,
checking their output 'power' (side note : moving average can be used as detector on their outputs)
and you can use them for sending too - just feed them white noise to the input :)

there are some advantages to that which this email is too short to contain ;)

el es

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