On Mon, Nov 3, 2008 at 2:36 AM, Matthew Smith <matt@xxxxxxxxxxxxxx> 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! 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 _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
