Swiftui ios create guitar tuner

Building a Guitar Tuner App in SwiftUI for iOS

SwiftUI has revolutionized app development for Apple platforms with its declarative syntax and powerful capabilities. In this article, we’ll create a fully functional guitar tuner app for iOS using SwiftUI and some essential frameworks like AVFoundation for audio analysis. By the end of this guide, you’ll have a basic tuner that listens to guitar strings and identifies their pitch.

Prerequisites

To follow along, ensure you have:

• Xcode installed (preferably the latest version).
• A basic understanding of Swift and SwiftUI.

Step 1: Setting Up the Project

1. Open Xcode and create a new project.
2. Choose App under the iOS section and click Next.
3. Name your project “GuitarTuner” and set the interface to SwiftUI.
4. Select a team for code signing and click Finish.

Once the project is ready, you’ll have a basic SwiftUI project structure.

Step 2: Integrating AVAudioEngine for Audio Input

To capture and process audio, we’ll use AVFoundation’s AVAudioEngine. Add the following import to your project:

import AVFoundation

Next, create a class to handle audio input and frequency detection:

import Foundation
import AVFoundation
import Accelerate

class AudioManager: ObservableObject {
    private var audioEngine: AVAudioEngine!
    @Published var frequency: Float = 0.0

    init() {
        setupAudioEngine()
    }

    private func setupAudioEngine() {
        audioEngine = AVAudioEngine()
        let inputNode = audioEngine.inputNode
        let bus = 0
        let inputFormat = inputNode.inputFormat(forBus: bus)

        inputNode.installTap(onBus: bus, bufferSize: 2048, format: inputFormat) { buffer, time in
            self.processAudioBuffer(buffer: buffer)
        }

        do {
            try audioEngine.start()
        } catch {
            print("Audio engine couldn't start: \(error.localizedDescription)")
        }
    }

    private func processAudioBuffer(buffer: AVAudioPCMBuffer) {
        guard let channelData = buffer.floatChannelData?[0] else { return }
        let channelDataArray = Array(UnsafeBufferPointer(start: channelData, count: Int(buffer.frameLength)))

        // Perform FFT (Fast Fourier Transform) to analyze frequencies
        let fftSize = 2048
        var realp = [Float](repeating: 0.0, count: fftSize / 2)
        var imagp = [Float](repeating: 0.0, count: fftSize / 2)

        var complexBuffer = DSPSplitComplex(realp: &realp, imagp: &imagp)
        channelDataArray.withUnsafeBufferPointer { ptr in
            ptr.baseAddress!.withMemoryRebound(to: DSPComplex.self, capacity: fftSize) {
                vDSP_ctoz($0, 2, &complexBuffer, 1, vDSP_Length(fftSize / 2))
            }
        }

        var magnitudes = [Float](repeating: 0.0, count: fftSize / 2)
        vDSP_zvmags(&complexBuffer, 1, &magnitudes, 1, vDSP_Length(fftSize / 2))

        if let maxIndex = magnitudes.indices.max(by: { magnitudes[$0] < magnitudes[$1] }) {
            let maxFrequency = Float(maxIndex) * (inputNode.outputFormat(forBus: bus).sampleRate / Float(fftSize))
            DispatchQueue.main.async {
                self.frequency = maxFrequency
            }
        }
    }

    func stopAudioEngine() {
        audioEngine.stop()
        audioEngine.inputNode.removeTap(onBus: 0)
    }
}

Step 3: Designing the User Interface in SwiftUI

Create a SwiftUI view to display the detected frequency and match it to guitar string notes:

import SwiftUI

struct ContentView: View {
    @StateObject private var audioManager = AudioManager()

    var body: some View {
        VStack {
            Text("Guitar Tuner")
                .font(.largeTitle)
                .padding()

            Text(String(format: "Frequency: %.2f Hz", audioManager.frequency))
                .font(.title2)
                .padding()

            Text(determineNoteName(for: audioManager.frequency))
                .font(.largeTitle)
                .foregroundColor(.blue)
                .padding()

            Spacer()
        }
        .onAppear {
            // Start the audio engine when the view appears
            audioManager.frequency = 0.0
        }
        .onDisappear {
            audioManager.stopAudioEngine()
        }
    }

    func determineNoteName(for frequency: Float) -> String {
        let notes = ["E", "A", "D", "G", "B", "E"]
        let standardFrequencies: [Float] = [82.41, 110.00, 146.83, 196.00, 246.94, 329.63]

        if let closestIndex = standardFrequencies.indices.min(by: { abs(standardFrequencies[$0] - frequency) < abs(standardFrequencies[$1] - frequency) }) {
            return notes[closestIndex]
        }

        return "-"
    }
}

Step 4: Running the App

1. Build and run the app on a real device (not the simulator, as it doesn’t support microphone input).
2. Play a guitar string near the device’s microphone.
3. Observe the displayed frequency and note.

Conclusion

With this project, you’ve built a basic guitar tuner app that listens to audio input, analyzes frequencies, and displays the closest guitar string note. While this implementation provides a foundational tuner, you can expand its functionality by improving frequency detection accuracy, adding visual tuning indicators, or supporting alternate tunings. SwiftUI and AVFoundation make it straightforward to create such interactive and practical apps.