Re: [Alsa-user] Output sample rate

[Rene H. <ren...@ke...>]

On 12-06-08 07:13, Demian Martin wrote:

> Computer audio and sample rate issues are popping up everywhere, driven 
> by the desire for high quality audio on PC's finally. On Windows and 
> Mac's its even harder to get it right.
> 
> In Alsa (and PC audio architecture in general) the system has a default 
> sample rate, usually set by the driver it seems, and usually 48 KHz.

Well, no. I have to comment on this since it gives the wrong impression 
about the design of things. ALSA drivers do not have or set a default 
sampling rate and whether or not "the system" does depends on you 
considering the dmix plugin intrinsic enough to be the system.

It is enabled by default (as also said in another message just now, if 
the card doesn't support mixing in hardware) which means you might be 
tempted to view it this way, but dmix is still only a fairly recent 
addition and implemented just under prressure of desktop sound needing 
to Just Work (after which everybody goes off and uses soundserver apps 
exclusively anyway it seems, but oh well...).

dmix is a plugin which indeed resamples to 48 kHz. It's easily disabled 
though by just using the "hw" ALSA device instead of the ALSA device 
named "default". To disable dmix from that device is also just a few 
config file edits away...

> Normally all the audio is resampled to this rate to permit mixing audio 
> from different sources (the system alert noises with your MP3 playback 
> for instance). However for those of us trying to get very high quality 
> audio out of the PC it's possible to get the driver, the audio player 
> and the card to cooperate and play the stream at its original "bit 
> perfect' sample rate. It requires alignment of the audio player app 
> (Xine in my case), Alsa, the driver for the card (the latest version of 
> the Juli@ driver) and it all seems to work right after many hours of 
> "tweaking".

You could've just disabled dmix... :-)

(by editing a card config file under /usr/share/alsa/cards or overriding 
things in /etc/alsa.conf or .asoundrc).

Rene.