[Linrad] Re: MAP65-not-IQ display oddities and doesn't decode

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Jeff,

> My windows XP install does has a problem where it seems to want to
> convert all
> audio to 48 kHz sampling rate.  For example using a sound card at 96
> kHz in
> linrad only shows +/-24 KHz of active spectrum, the rest looks
> filtered out.
"a sound card" Do you know that the soundcard is capable of sampling 
at 96 kHz? As far as I have been able to find out, there is no way
to find out hardware capabilities under Windows by quering the device.
Linrad therefore allows you to set any sampling speed. Windows will 
silently do the rate conversion in software. (When up-converting
the increased bandwidth is of course totally useless.)

I can not give the answers about map65, but you might press 'T'
to get timing info in Linrad. On my laptop I can ask for 96000 Hz
and Linrad evaluates it to 95350. When I ask for anything between
96100 and 97000 I get 96650 Hz. The fractional resampler does not
allow finetuning of the hardware. Somewhere in the system settings you
can change the quality of the resampler. Trade quality vs cpu load.
I do not know if that could allow a finer stepping in the resampling
ratio. In any case, MAP65 will require a reasonably correct sampling
speed and not all soundcards deliver that.

73

Leif / SM5BSZ

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