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[Linrad] Quartet Soundcard and Linrad and Windows
- Subject: [Linrad] Quartet Soundcard and Linrad and Windows
- From: w3sz <gmail.com; 73w3sz@xxxxxxxxxxxxxxxx>
- Date: Mon, 26 Jan 2009 23:35:31 -0500
I already relayed this information to Leif, but I think it will be
useful to the list as well. This description applies to Windows XP.
I did the experiment of running Linrad03-01 at sampling speeds of
48 kHz, 96 kHz, and 192 kHz with WAVEFORMATEXTENSIBLE set to 'y' or 'n'.
With it set to 'y', both 96 kHz and 192 kHz sampling speeds had the
useful signal bandwidth reduced to 48 kHz; outside of the central 48 kHz
of spectrum the signal was reduced to zero. With it set to 'n', both
sampling speeds had the useful signal width at full value: 96kHz or 192
kHz respectively, as selected.
With 48 kHz sampling speed, the full 48 kHz is seen with either 'y' or
'n' selected for WAVEFORMATEXTENSIBLE.
With WAVEFORMATEXTENSIBLE set to 'n' there is no choice between 16 and
24 bits, but only 16 bits is permitted regardless of sampling speed chosen.
So, although one selects 96 or 192 kHz with WAVEFORMATEXTENSIBLE,
Windows decides to do something else. It gives the appearance of
applying a low pass filter limiting signal to +/- 24 kHz of zero, but it
may really be a resampling effect. While I knew that cheap 'on board'
sound was subject to resampling under Windows, I am surprised to find a
quality sound card treated this way by Windows!
The solution for me is to run with WAVEFORMATEXTENSIBLE = 'n' and thus
use 16 bits. Then the sampling is as desired.
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