[Solved] If the PDC of FX oversampled by x times is not a multiple of x, the output i

[lewloiwc]

If the PDC of an oversampled FX by x times is not a multiple of x, the output is delayed by (PDC%x/x) spls.


To be precise, when the oversampling of REAPER is 4x, PDC from 0 to 3 is actually 0, from 4 to 7 is actually 4, and from 40 to 43 is actually 40, so I think the cause is that the delay is shifted from the delay expected by the plug-in.

In my estimation if the exact implementation,

@init
pdc_delay = 1;
pdc_bot_ch = 0;
pdc_top_ch = 2;

If this is used with 2x oversampling, the output should be 0.5 samples earlier, and if used with 4x oversampling, the output should be 0.25 samples earlier.

Here is the JSFX used for verification

desc:_x_pdc_and_x_delay

slider1:x_slider=0<0,30,1>x



@init //----------------------------------------------------------------

ext_nodenorm = 1;

function delay(x0,x1,mem,delay)
(
    delay <= 0 ? (
        this.0 = x0;
        this.1 = x1;
    ) : (
        this.0 = mem[this.cnt];
        this.1 = mem[this.cnt + 1];
        
        mem[this.cnt] = x0;
        mem[this.cnt + 1] = x1;
        
        this.cnt < delay*2 - 2 ? (
            this.cnt += 2;
        ) : (
            this.cnt = 0;
        );
    );
);



@slider //----------------------------------------------------------------

pdc_delay = x_slider;
pdc_bot_ch = 0;
pdc_top_ch = 2;



@sample //----------------------------------------------------------------

delay.delay(spl0,spl1,0,x_slider);

spl0 = delay.0;
spl1 = delay.1;

desc:_pdc_and_delay

slider1:pdc_slider=0<0,30,1>PDC
slider2:delay_slider=0<0,30,1>Delay



@init //----------------------------------------------------------------

ext_nodenorm = 1;

function delay(x0,x1,mem,delay)
(
    delay <= 0 ? (
        this.0 = x0;
        this.1 = x1;
    ) : (
        this.0 = mem[this.cnt];
        this.1 = mem[this.cnt + 1];
        
        mem[this.cnt] = x0;
        mem[this.cnt + 1] = x1;
        
        this.cnt < delay*2 - 2 ? (
            this.cnt += 2;
        ) : (
            this.cnt = 0;
        );
    );
);



@slider //----------------------------------------------------------------

pdc_delay = pdc_slider;
pdc_bot_ch = 0;
pdc_top_ch = 2;



@sample //----------------------------------------------------------------

delay.delay(spl0,spl1,0,delay_slider);

spl0 = delay.0;
spl1 = delay.1;

Windows 10 Home | REAPER v6.78+dev0404/win64

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