Re: [LAU] Intel-hda jack low latency howto

On Mon, 03 Nov 2008 19:06:49 +1030
Matthew Smith <matt@email-addr-hidden> wrote:

> Quoth Arnold Krille at 2008-11-03 18:57...
> > One of the design decisions of the hda is to support 48 kHz for
> > DVD. And to make it simple they only support 48kHz in hardware.
> > While you can open the device with lower samplingrates this will
> > get resampled to 48kHz either by the driver or the chip. And as you
> > don't know what quality that resampling algorithm has (remember the
> > only thing "high" in the hda is the name), you will want to use
> > 48kHz from start to end and only downsample to 41kHz directly
> > before creating the cd master. Which has the advantage that you can
> > use the fine libsamplerate instead...
>
> Interesting. I wonder, does it explain this?
>
> Whilst I use fully external ADC/DACs for music use, with the HDA card
> disabled, for everyday use - which means Skype since I don't do any
> other sort of everyday audio - I use a Zoom H2 as my microphone/input
> sound card and have headphones plugged into the on-board HDA.
>
> If I have the H2 set to sample at its default of 44.1ksps, playing
> back my voice on a Skype test call, I sound like someone who should
> be guarding a hareem ;-) Setting the H2 to sample at 48ksps, I sound
> my <cough/> "normal" self.
>
> Would it just be at the receiving end of the loop that my voice is
> pitch-shifting, or is there some funny re-sampling going on in the
> Skype software?
>
> I'm just so glad that I tested the sound before calling a client!
>
> Cheers
>
> M

It sounds like no resampling is happening there. If you play back
48kHz audio at 44.1kHz it will be slower and at lower pitch. It's just
playing back fewer samples per second than it's supposed to.

Philipp
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Received on Mon Nov 3 12:15:02 2008