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[Linrad] Re: Quartet Soundcard and Linrad and Windows

HI Jeff,

I am far from an expert in this area.  Leif suggested to me that what I 
am seeing might be a function of Linrad's using the standard drivers 
rather than ASIO or other driver.  The Realtek AC97 in my laptop 
resamples 'silently', I know from experience.

If you set WAVEFORMATEXTENSIBLE to 'n' then it appears that resampling 
will be prevented, at least in this particular case.

Others on this list are experts in this area, and I will defer to them...


Roger Rehr

On 1/27/2009 12:05 AM, wa1hco@xxxxxxxxx wrote:
> Roger...
> Do you think this applies to other drivers as well?  After playing with some SB drivers, windows started behaving this way with Rocky and all sound cards.
> Windows may have a mode where it does this and a mode where it doesn't.  I would like to know how to switch that mode back.
> Jeff, wa1hco
> Sent via BlackBerry from T-Mobile
> -----Original Message-----
> From: w3sz<73w3sz@xxxxxxxxx>
> Date: Mon, 26 Jan 2009 23:35:31
> To: linrad@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> Subject: [Linrad] Quartet Soundcard and Linrad and Windows
> Hi All,
> 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.
> 73,
> Roger Rehr
> W3SZ
> http://www.nitehawk.com/w3sz
> >

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