How to create a simple EQ like AVAudioUnitEQ in AudioKit?

[Volodymyr-13]

How to create a simple EQ like AVAudioUnitEQ in AudioKit?

[NickCulbertson]

Haha! It does make some things easier and others parts are about the same.

Here is a better example making a 5-pole EQ. It needs to be refactored, but it works.

import AudioKit
import AudioKitEX
import AudioKitUI
import AVFoundation
import SoundpipeAudioKit
import SwiftUI
import Controls

/// AudioKit version of Apple's EQ Audio Unit
public class AppleEQ: Node {
    public var equalizerAU: AVAudioUnitEQ
    
    let input: Node
    
    /// Connected nodes
    public var connections: [Node] { [input] }
    
    /// Underlying AVAudioNode
    public var avAudioNode: AVAudioNode
    
    /// globalGain (Default 0) -96 -> 24
    public var globalGain: AUValue = 0 {
        didSet {
            equalizerAU.globalGain = globalGain
        }
    }
    
    public init(_ input: Node, bands: Int = 5, globalGain: AUValue = 0) {
        equalizerAU = AVAudioUnitEQ(numberOfBands: bands)
        self.input = input
        avAudioNode = equalizerAU
    }
}

class AppleEQConductor: ObservableObject, ProcessesPlayerInput {
    let engine = AudioEngine()
    let player = AudioPlayer()
    var filter: AppleEQ
    let dryWetMixer: DryWetMixer
    let buffer: AVAudioPCMBuffer
    
    @Published var frequency1 : Float = 100.0 {
        didSet {
            filter.equalizerAU.bands[0].frequency = frequency1
        }
    }
    
    @Published var gain1 : Float = 0.0 {
        didSet {
            filter.equalizerAU.bands[0].gain = gain1
        }
    }
    
    @Published var frequency2 : Float = 300.0 {
        didSet {
            filter.equalizerAU.bands[1].frequency = frequency2
        }
    }
    
    @Published var gain2 : Float = 0.0 {
        didSet {
            filter.equalizerAU.bands[1].gain = gain2
        }
    }
    
    @Published var frequency3 : Float = 1000.0 {
        didSet {
            filter.equalizerAU.bands[2].frequency = frequency3
        }
    }
    
    @Published var gain3 : Float = 0.0 {
        didSet {
            filter.equalizerAU.bands[2].gain = gain3
        }
    }
    
    @Published var frequency4 : Float = 4000.0 {
        didSet {
            filter.equalizerAU.bands[3].frequency = frequency4
        }
    }
    
    @Published var gain4 : Float = 0.0 {
        didSet {
            filter.equalizerAU.bands[3].gain = gain4
        }
    }
    
    @Published var frequency5 : Float = 10000.0 {
        didSet {
            filter.equalizerAU.bands[4].frequency = frequency5
        }
    }
    
    @Published var gain5 : Float = 0.0 {
        didSet {
            filter.equalizerAU.bands[4].gain = gain5
        }
    }
    
    @Published var globalGain : Float = 0.0 {
        didSet {
            filter.equalizerAU.globalGain = globalGain
        }
    }
    
    init() {
        buffer = Cookbook.sourceBuffer
        player.buffer = buffer
        player.isLooping = true
        
        filter = AppleEQ(player, bands: 5)
        dryWetMixer = DryWetMixer(player, filter)
        engine.output = dryWetMixer
        
        filter.equalizerAU.bands[0].frequency = 100.0
        filter.equalizerAU.bands[1].frequency = 300.0
        filter.equalizerAU.bands[2].frequency = 1_000.0
        filter.equalizerAU.bands[3].frequency = 4_000.0
        filter.equalizerAU.bands[4].frequency = 10_000.0
        
        for i in 0..<5 {
            filter.equalizerAU.bands[i].gain = 0
            filter.equalizerAU.bands[i].bypass = false
            filter.equalizerAU.bands[i].filterType = .parametric
        }
    }
}

struct AppleEQView: View {
    @StateObject var conductor = AppleEQConductor()
    
    var body: some View {
        VStack {
            PlayerControls(conductor: conductor)
            HStack {
                VStack {
                    CookbookKnob(text: "Frequency 1", parameter: $conductor.frequency1, range: 20...20000)
                    CookbookKnob(text: "Gain 1", parameter: $conductor.gain1, range: -96...24)
                }
                VStack {
                    CookbookKnob(text: "Frequency 2", parameter: $conductor.frequency2, range: 20...20000)
                    CookbookKnob(text: "Gain 2", parameter: $conductor.gain2, range: -96...24)
                }
                VStack {
                    CookbookKnob(text: "Frequency 3", parameter: $conductor.frequency3, range: 20...20000)
                    CookbookKnob(text: "Gain 3", parameter: $conductor.gain3, range: -96...24)
                }
                VStack {
                    CookbookKnob(text: "Frequency 4", parameter: $conductor.frequency4, range: 20...20000)
                    CookbookKnob(text: "Gain 4", parameter: $conductor.gain4, range: -96...24)
                }
                VStack {
                    CookbookKnob(text: "Frequency 5", parameter: $conductor.frequency5, range: 20...20000)
                    CookbookKnob(text: "Gain 5", parameter: $conductor.gain5, range: -96...24)
                }
                CookbookKnob(text: "Global Gain", parameter: $conductor.globalGain, range: -96...24)

            }
            DryWetMixView(dry: conductor.player,
                          wet: conductor.filter,
                          mix: conductor.dryWetMixer)
            
        }
        .padding()
        .cookbookNavBarTitle("Equalizer Filter")
        .onAppear {
            conductor.start()
        }
        .onDisappear {
            conductor.stop()
        }
    }
}

[NickCulbertson]

Hello! I’ve not worked with the AudioPlayer much in AudioKit, but I think I see what's up. It looks like these lines are where it is playing again in the seek method: https://github.com/AudioKit/AudioKit/blob/2f69d1916f94734e42a9482a54b4c63bb6a58667/Sources/AudioKit/Nodes/Playback/AudioPlayer/AudioPlayer%2BPlayback.swift#L114 I imagine that method would need to be edited to remove that part in your case. The best way to experiment with it is to drag a local copy of the AudioKit package into your project for editing. Here is how to do that: https://youtu.be/QTrsO6vOHAM?t=182 If you find a good solution (which may just be removing those two lines of code) you could submit a Pull Request with a seekStopped() method so that you can keep using the release version. Thanks, Nick

…

On Feb 2, 2024, at 6:04 PM, Oleksandr Stepanov ***@***.***> wrote: @NickCulbertson <https://github.com/NickCulbertson> Hi, we used AudioKit, awesome! Many thanks and respect! Could you please give an advice on "seek" method? For example if I try to seek my audio track when paused, the track will start to play in spite of the pause. I understand why but can it be fixed so that it would depend on the previous player state (was playing or paused) Thanks! — Reply to this email directly, view it on GitHub <#2897 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAGI66T2J2NLJ3AYZA3AIVDYRVWJTAVCNFSM6AAAAABCNOKRQWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMRUHA4DCMZYGE>. You are receiving this because you were mentioned.

[NickCulbertson]

This can be done, but is a tough one to generalize since AVAudioUnitEQ(numberOfBands: ) is doing some work under the hood with [AVAudioUnitEQFilterParameters].

Here is a quick implementation you can try running in the Cookbook as a starting point. I'm sending a constant when initializing AVAudioUnitEQ(numberOfBands: 5) that you can change to whatever value you need. In the example the knob updates all frequencies just to show how to map the parameters to a local variable.

import AudioKit
import AudioKitEX
import AudioKitUI
import AVFoundation
import SoundpipeAudioKit
import SwiftUI

/// AudioKit version of Apple's EQ Audio Unit
///
public class AppleEQ: Node {
    public var equalizerAU = AVAudioUnitEQ(numberOfBands: 5)

    let input: Node

    /// Connected nodes
    public var connections: [Node] { [input] }

    /// Underlying AVAudioNode
    public var avAudioNode: AVAudioNode
    
    /// globalGain (Default 0) -96 -> 24
    public var globalGain: AUValue = 0 {
        didSet {
            equalizerAU.globalGain = globalGain
        }
    }

    public init(_ input: Node, globalGain: AUValue = 0) {
        self.input = input
        avAudioNode = equalizerAU
    }
}

class AppleEQConductor: ObservableObject, ProcessesPlayerInput {
    let engine = AudioEngine()
    let player = AudioPlayer()
    let filter: AppleEQ
    let dryWetMixer: DryWetMixer
    let buffer: AVAudioPCMBuffer
    
    @Published var frequency : Float = 0.0 {
        didSet {
            for i in 0..<5 {
                filter.equalizerAU.bands[i].frequency = frequency * Float(i)
            }
        }
    }
    
    init() {
        buffer = Cookbook.sourceBuffer
        player.buffer = buffer
        player.isLooping = true

        filter = AppleEQ(player)
        dryWetMixer = DryWetMixer(player, filter)
        engine.output = dryWetMixer
        
        for i in 0..<5 {
            filter.equalizerAU.bands[i].frequency = Float(100*i)
            filter.equalizerAU.bands[i].gain = 20
            filter.equalizerAU.bands[i].bypass = false
            filter.equalizerAU.bands[i].filterType = .parametric
        }
    }
}

struct AppleEQView: View {
    @StateObject var conductor = AppleEQConductor()

    var body: some View {
        VStack {
            PlayerControls(conductor: conductor)
            HStack {
                CookbookKnob(text: "Frequency", parameter: $conductor.frequency, range: 20...20000)
                DryWetMixView(dry: conductor.player,
                              wet: conductor.filter,
                              mix: conductor.dryWetMixer)
            }
        }
        .padding()
        .cookbookNavBarTitle("Equalizer Filter")
        .onAppear {
            conductor.start()
        }
        .onDisappear {
            conductor.stop()
        }
    }
}

[Volodymyr-13]

@NickCulbertson Thanks! I will try!

I just thought that AudioKit was designed to make life easier for the developer) but it turns out I need to suffer so much more)