Subject: Re: audio widgets etc, was Re: [linux-audio-dev] Is ladspa actually la-dsp-a? Is JACK the ultimate solution?
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Wed Jun 09 2004 - 16:37:31 EEST
On Wed, Jun 09, 2004 at 02:35:56PM +0100, Chris Cannam wrote:
> On Wednesday 09 Jun 2004 1:50 pm, Steve Harris wrote:
> > A little bit of meter standardisation wouldn't hurt - eg. the point
> > at which people show red seems to vary a lot, which has been
> > confusing for users.
>
> Also is there a common convention for how dB levels map to positions
> on a fader or meter?
Yes, IEC-268:
float iec_scale(float db)
{
float def = 0.0f; /* Meter deflection %age */
if (db < -70.0f) {
def = 0.0f;
} else if (db < -60.0f) {
def = (db + 70.0f) * 0.25f;
} else if (db < -50.0f) {
def = (db + 60.0f) * 0.5f + 5.0f;
} else if (db < -40.0f) {
def = (db + 50.0f) * 0.75f + 7.5;
} else if (db < -30.0f) {
def = (db + 40.0f) * 1.5f + 15.0f;
} else if (db < -20.0f) {
def = (db + 30.0f) * 2.0f + 30.0f;
} else {
def = (db + 20.0f) * 2.5f + 50.0f;
}
return def;
}
It also defines which points you should mark on your scale.
- Steve
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