Re: [LAD] vu-meter DSP

On Sat, Jul 27, 2013 at 06:32:33PM +0200, Robin Gareus wrote: Yes. The VU was the easiest one. First get the overshoot right, that's easy. Then plot the output of the DSP code, note the time when it reaches 99%, adjust filter coefficient. For the IEC I and II meters it's a lot more difficult. They are specified by a drop rate (easy), and their response to various burst test signals. For the real ones, the result is the combined effect of a non-linear pseudo-peak detector, a non-linear mapping to the meter scale, and the ballistics of the actual mechanical meter (not always driven from a constant impedance, hence variable). That is not something that will correspond to some readable equations. The only way to get those right is to create some mathematical model that you believe could do the right thing, then tune its parameters by trial and error. If that fails try another model, until you get well within the allowed error margins. The most difficult one was the CCIR-468 response implemented in jnoisemeter - that is a really weird one - the combination of two interacting pseudo-peak detectors. There is an (unofficial) equation for it which is rather useless and fills an A4 page. TNX ! But I'm not really surprised - I wrote the jmeters code because I found *nothing* that really worked as it should have. And as your tests have shown again, most don't even come close. The videos are fun to watch... BTW, while I have no problem with 'real' VUs, a bargraph display - even if correct - looks somewhat hyperkinetic to my taste... I wouldn't stand looking at it for too long. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow)