[SOLVED] 10 Band Equaliser using NOVOCAINE

10 Band Equaliser using NOVOCAINE

Im trying to build a 10 band Equaliser using NOVOCAINE. I copied the Equaliser.mm's code in viewWillAppear, and added 9 more Sliders in the xib file, and changed IBAction code too this :

-(void)HPFSliderChanged:(UISlider *)sender {
PEQ[sender.tag - 1].centerFrequency = sender.value;
NSLog(@"%f",sender.value);
}

What I want to know is if I am doing this the right way or not ? and the what will be range of the Sliders ? Like in HPF example, the slider range is 2k to 8k. Need some guidance here.

Thanks.

Solution

EDIT: after your comment, I think it is clearer what you are asking.

Take the code to instantiate a NVPeakingEQFilter:

        NVPeakingEQFilter* PEQ = [[NVPeakingEQFilter alloc] initWithSamplingRate:self.samplingRate];
        PEQ.Q = QFactor;
        PEQ.G = gain;
        PEQ.centerFrequency = centerFrequencies;

you need define 3 parameters: Q, G, and centerFrequency. Both Q and centerFrequency are usually fixed (QFactor in my case is a constant equal to 2.0).

So, you have 10 sliders: each one corresponds to a fixed centerFrequency. I suggested iTunes values: 32Hz, 64Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz, 16KHz. You do not want to change those values when the slider value changes.

What you want to change when the slider value changes is the gain (G). At init time, G can be set to 0.0. This means "no amplification/attenuation".

When the slider moves, you change G, so actually you would do:

PEQ[sender.tag - 1].G = sender.value * kNominalGainRange;

where kNominalGainRange is 12.0, so if sender.value goes from -1.0 to +1.0, G goes from -12 to +12.

Hope this helps.

What I want to know is if I am doing this the right way or not ?

you do not show much code, but HPFSliderChanged seems correct. If you have any specific issue you should describe it and post more code.

and the what will be range of the Sliders ?

Actually, there is no rigid rule when it come to equalisers. iTunes goes from -12db to +12db, but you could use different ranges (with the only caveat being distortion).

Like in HPF example, the slider range is 2k to 8k. Need some guidance here.

again, you can take iTunes equaliser as an example (32Hz, 64Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz, 16KHz), or you can google for images of real equalisers and see which bands they use.