soundcard trouble with Wolf

[Andre' Kesteloot]

Alberto di Bene wrote:

> DL4YHF@aol.com wrote:
> >
> [snip]
> > The precise sample rates of the soundcard, running at a nominal sample rate
> > of 8000 samples per second, were **DIFFERENT** for TX (D/A conversion) and RX
> > (A/D conversion)  !
> [snip]
>
> Wolf and the group,
>      in the Windows world a new standard is emerging, the AC97 standard for
> sound cards. How does that affect us ? With AC97, the hardware samples *always*
> at the maximum sampling rate of 44.1 or maybe 48 kHz.
> When a program opens the sound subsystem specifying a different sampling rate,
> the driver does a downsampling of the 44.1 (48) kHz stream when opening for input,
> and an upsampling, probably with zero-padding, when opening for output.
>
> I have verified this in practice. On my IBM Thinkpad, I am able to start
> simultaneously several programs that use the sound card (sound chip in this case),
> and they work correctly even if they specify different sampling rates !
> At first I didn't believe to my eyes, but then I read about the AC97 standard.
>
> The implications of this are that in the process of down/up sampling, some roundoff
> errors can happen, and the actual sampling rate, as seen by the application,
> can differ by a slight amount from what specified. For the normal use of the
> sound cards, i.e. games, this has no consequences. Not so for a more serious use.
> So the advice is to stay away, whenever possible, from sound cards whose drivers
> implement the AC97 standard, which, I'm afraid, is what Bill want us to use.
>
> 73  Alberto  I2PHD