[linux-audio-dev] ALSA features.

[Dan Mills]

On Sunday 04 September 2005 22:12, Jussi Laako wrote:
> On Sat, 2005-09-03 at 21:14 +0100, Dan Mills wrote:
> > I don't think this is right, a signal **level** can be measured against a
> > known reference level, and for metering it is important to know what this
> > is, but a **gain** value is **always** unitless (You are multiplying a
> > signal which has units by a scalar value).
>
> The thing here, is that I would like to know which actual output level
> results when some given sample value is written with some gain setting.
>
> Or I could determine actual input level by reading sample value and
> input gain setting.

Indeed! 
The good stuff typically documents (for example) an analogue output level of 
+4dBu for a sample 16db below full scale (or equivalently) that zero dBfs is 
+20dBu. Note that the reconstruction filter overshoot will actually put the 
peak output level up around +22dBu in this case!

With pro hardware that does not have integrated 'gain' controls (or at least 
calibrates them), this is easy, otherwise an audio milivoltmeter (or 'scope) 
and a simple program is required.  

Regards, Dan.