Re: [PATCH] Adds dB gain to alsa-driver, alsa-lib.

[Lee Revell <rlrevell@joe-job.com>]

On Thu, 2005-12-15 at 19:06 +0000, James Courtier-Dutton wrote:
> Lee Revell wrote:
> > On Thu, 2005-12-15 at 18:34 +0000, James Courtier-Dutton wrote:
> > 
> >>Hi,
> >>
> >>I have implemented dB gain reporting for ALSA mixer controls.
> >>By applying the attached patches to alsa-driver and alsa-lib, one will 
> >>then see dB values appear in alsamixer. (I added support to alsamixer a 
> >>long time ago)
> >>
> >>Currently, only the snd-ca0106 sound card reports the values.
> >>
> >>If the method is agreed upon, I will extend it to many more sound cards.
> > 
> > 
> > Can you briefly explain the process for adding this feature to an
> > existing driver (IOW say you have no docs just a vendor-obfuscated or
> > RE'd driver, how do you determine db_scale)?
> > 
> > Lee
> > 
> 
> There is no point in RE the windows driver, because windows does not 
> display dB values.
> You do it simply by measurements.
> You calibrate a line-in from a sound card that has documentation.
> Then connect it to the suspect sound card's output and measure it.
> 
> Same for mic/line in.
> 
> I will be implementing this dB support on creative cards first, as I 
> have some details for them. We have docs for all AC97 controls. So 
> hopefully that won't leave many other controls to do.
> 
> Please note, my last patch has a few errors in it, so that it does not 
> always supress the dB display with unsupported cards. I have fixed this 
> in my own tree, but I would like full feedback first.
> 
> Which sound card do you have?

Two Creative cards (an SBLive platinum CT4760 and Audigy2 ZS platinum)

Lee



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