Peak plugin with one register less

eyagos · Dec 4, 2003, 04:20 PM

Well, the actual code of peak is

Quote:

; Registers
input peak_l, peak_r;
static result_l=0x0, result_r=0x0, resolution=0x1f;
temp tmp

; Code
log tmp, peak_l, resolution, 0x1;
limit result_l, tmp, tmp, result_l;
log tmp, peak_r, resolution, 0x1;
limit result_r, tmp, tmp, result_r;

Here the logarithm of the input (in abs value) is taken, and the dll uses a formula to convert it into the sacle of the vumeter gaph.

But is not necesary to take the logarithm of the input. If you just take the abs of the inputs (the resolution=0x1F register is not needed there), and uses a different formula in the dll to ake the conversion, the result would be exactly the same

Quote:

; Registers
input peak_l, peak_r;
static result_l=0x0, result_r=0x0
temp tmp

; Code
tstneg tmp, peak_l, peak_l, 0x0;
limit result_l, tmp, tmp, result_l;
tstneg tmp, peak_r, peak_r, 0x0;
limit result_r, tmp, tmp, result_r;

Only modifying the conversion formula in the dll, the result would be exactly the same.

**Eugene Gavrilov** · Dec 4, 2003, 05:22 PM

sounds reasonable. I'll have a look -- thanks

/E

Max M. · Dec 13, 2003, 02:36 PM

(btw. E. this is exactly like in ufx's peakmeter and i wrote to you about this)
In fact, "log" (as well as "exp") instruction of fx8010 is just an approximation so it gives ~0.5dB error at every "2*(n+1)*3db" peakmeter value... So method with "linear" dsp code and linear->logarithmic conversion with kxl (e.g. using C) is preferred...

Dec 13, 2003, 02:36 PM	#3
Max M. h/h member-shmember Join Date: Dec 2002 Location: Evil Empire Posts: 2,639 Rep Power: 69	(btw. E. this is exactly like in ufx's peakmeter and i wrote to you about this) In fact, "log" (as well as "exp") instruction of fx8010 is just an approximation so it gives ~0.5dB error at every "2(n+1)3db" peakmeter value... So method with "linear" dsp code and linear->logarithmic conversion with kxl (e.g. using C) is preferred... __________________ Last edited by Max M.; Dec 13, 2003 at 03:45 PM.

Dec 4, 2003, 05:22 PM	#2
Eugene Gavrilov kX Project Lead Programmer and Coordinator Join Date: Dec 2002 Posts: 3,119 Rep Power: 75	sounds reasonable. I'll have a look -- thanks /E