David Henningsson david.henningsson at
Mon Jan 2 10:06:37 UTC 2012

On 12/27/2011 08:44 PM, Len Ovens wrote:
> Tried some documentation. It is here:
> There are two live links. One for internal sound chips and one near the
> bottom about dual monitors. Any comments are welcome.
> I have used a minimum of formating, none of it hard formating. So it
> should be easy to read no matter the size of the browser window.

It is good that you are trying to write documentation, but I had a look at

...and I don't find it to be accurate. You seem to take the experience 
of your own HDA Codec and assume it applies to all HDA codecs, e g "The 
input preamps in these sound cards are generally noisy so lets try not 
to use them."

"Clock rates: The first thing to know about the HDA chipsets is that the 
adc operates at one clock rate." <- What is the source for that information?

"All other rates are achieved by firmware in a DSP." "On some hardware 
the maximum rate can be found with this method: Determining the sample 
rate of a sound card." <- If the rate was changed in the firmware, user 
space would not be able to detect that using that method.

"While the internal mic is obviously a mono device" <- this is wrong - a 
lot of machines have stereo internal mics. In Windows 7, this is used 
for beam forming and noise reduction algorithms.


Also avoid links that points to how to change your system if you have 
some particular hw, e g "No internal mic on Acer Aspire" - these links 
become outdated quickly as we fix those bugs.

David Henningsson, Canonical Ltd.

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