3 Nov
2008
3 Nov
'08
12:02 p.m.
On Mon, Nov 3, 2008 at 2:36 AM, Matthew Smith <matt(a)smiffytech.com> wrote:
Quoth Arnold Krille at 2008-11-03 18:57...
That can happen if you set the JACK sample rate to -r44100. JACK's
ALSA backend requests a sample rate "near" the requested value. ALSA
responds with 48000 because that is all the HDA device actually
supports. Since JACK does not resample, the pitch effectively gets
shifted up a step or so with the tempo gets speeded up as well.
This is not good. We should probably add a specific test for this
too-frequent gotcha in the ALSA backend. If it requests 41000 and
gets 48000 it should at least complain, and perhaps even fail to start
in that case.
--
joq
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!