[alsa-devel] wrong decibel data?

[Raymond Yau]

2010/6/14 James Courtier-Dutton <james.dutton at gmail.com>

> On 14 June 2010 09:33, Colin Guthrie <gmane at colin.guthr.ie> wrote:
> > 'Twas brillig, and Raymond Yau at 14/06/10 01:25 did gyre and gimble:
> >> if your sound card have ac97 codec ., you can use audacity to record the
> >> output from hw:0,0 and you will see clipping occur when you set "PCM"
> volume
> >> above 0dB
> >
> > So the standard response is "don't do that then" :)
> >
> > That's why the base volume is shown to the user via GUIs so that they
> > can gauge the best point on the slider to use. Currently there is no
> > indication with alsa sliders at which point the 0dB "sweet spot" lies.
> >
>
> What do you mean.
> If you use "alsamixer", dB values are shown so it is easy to find the
> 0dB "sweet spot".
> I think it is pulse audio that hides this information when it combines
> two alsa mixer controls into one pulseaudio control.
>


The base volume seem to be the software 0dB point , (no software
gain/atten), but the user want the hardware 0dB point (no hardware
gain/atten if the hardware can provide hardware gain

This hardware 0dB point is extremely important when you want to record using
line in and line out