[pulseaudio-discuss] Forcing sample rate, and mixer weirdness

Christian Iversen chrivers at iversen-net.dk
Tue May 21 09:15:07 PDT 2013

Hey guys

Just two more questions. I have an external sound card, the Focusrite 
Scarlett 2i2 USB. I'm trying to make it work optimally, and I'm almost 
there. Just 2 more issues:

1) It takes 500-1000ms to change sample rates (ridiculous, I know).

Which is why I would like to avoid doing that, at all cost. I have a 
plenty fast CPU, so it's not really a problem to do occasional 
resampling. Most of the source material is in 44.1kHz anyway, so the odd 
48kHz source should just be downsampled.

How can I force pulseaudio to use a 44.1kHz output rate at all times? 
I've tried googling, and it was suggested putting

default-sample-rate = 44100

In ~/.pulse/daemon.conf. But that doesn't seem to change anything. Is 
there another way?

2) This particular USB sound card has no hardware volume controls, 
except physical tuning knobs. When I use kmix to turn the volume 
up/down, it indeed works, and as far as I can tell, it communicates with 
PA to do so. (and it works just fine).

However, the first time I play a source after PA has started, the PA 
volume is at 100%. Which means that if I forget to turn the volume down 
in kmix, my USB device becomes a Sound Blaster (mehehe..).

Interestingly, kmix remembers that the volume is supposed to be around 
~30%, so when I turn it one step down (I have a hotkey for that), it 
goes to ~25% immediately, instead of just the second-highest step. I 
guess this is because kmix remembers where the volume was supposed to be 
at, and not because of PA's as such.

However, remembering and restoring the volume between reboots works fine 
with all other sound cards, which have hardware mixers. What could be 
causing these problems? Who is responsible for restoring volume in this 
case - is it kmix, PA, or a combination?

Is this happening because the restore code does not want to enforce 
software volume control?

Med venlig hilsen
Christian Iversen

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