Am Donnerstag, den 21.05.2009, 21:07 +0100 schrieb Chris Cannam: > On Thu, May 21, 2009 at 8:48 PM, Chris Cannam > <[email protected]> wrote: > > There is an IEC standard for this mapping in meters (IEC 60-268-18) > > which works OK for faders as well if extended in a sensible way down > > to -inf, particularly if you don't want to go above 0dB. It divides > > the range up into several sections which are individually linear in > > dB. There's code for this mapping in several places, including > > base/AudioLevel.cpp in the Rosegarden source code. > > Actually I might as well summarise here, not least because I've > noticed the RG code does not in fact implement exactly what's in the > standard. > > The standard has the top 25% of the meter covering 0dB down to -9dB; > the next 25% covering -9 to -20; the next 20% covering -20 to -30; the > next 15% covering -30 to -40; the next 7.5% covering -40 to -50; the > next 5% covering -50 to -60; and the last 2.5% covering -60 to -Inf. > Each of those ranges is linear in dB. > > The numbered levels are 0, -5, -10, -15, -20, -30, -40, -50, -60. > > Ticks are per dB down to -20, then only at numbered positions, with an > additional tick at -45dB (why?) > > This is actually quite different from the cubic mapping; it gives you > a lot more space in -10 to -20 relative to 0 to -10. That suggests > that you can get away with quite a few different mappings in practice. > > > A cubic mapping is also good. > > In Rosegarden we actually switched from a cubic mapping to one based > on the IEC meter mapping, many years ago, because "it seemed like a > good idea at the time". I've never really made up my mind whether it > turned out better or worse. Nowadays I'd probably go for cubic, since > it's a one-liner to code. > > > Chris
Here is a simple discription for a fader taper like that on musikdsp.org http://www.musicdsp.org/archive.php?classid=5#94 _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
