C4Sample audio metering example

C4WorkSpace.m

#import "C4WorkSpace.h"

@implementation C4WorkSpace {
    C4Sample *s;
    C4Timer *meterUpdateTimer;
    C4Shape *peak, *avg;
}

-(void)setup {
    s = [C4Sample sampleNamed:@"C4Loop.aif"];
    s.loops = YES;
    s.meteringEnabled = YES;
    [s prepareToPlay];
    [s play];

    CGPoint pts[2] = {
        CGPointMake(self.canvas.width / 3, self.canvas.height),
        CGPointMake(self.canvas.width / 3, 0)
    };
    avg = [C4Shape line:pts];
    
    pts[0].x *= 2;
    pts[1].x *= 2;
    peak = [C4Shape line:pts];
    
    [self.canvas addObjects:@[avg,peak]];
    
    meterUpdateTimer = [C4Timer timerWithInterval:1/30.0f target:self method:@"updateMeters" repeats:YES];
    [meterUpdateTimer start];

}

-(void)updateMeters {
    [s updateMeters];
    avg.strokeEnd = [C4Math pow:10 raisedTo:0.05 * [s averagePowerForChannel:0]];
    peak.strokeEnd = [C4Math pow:10 raisedTo:0.05 * [s peakPowerForChannel:0]];
}

@end