AudioVisualizer component (Bars) (#14)

https://github.com/user-attachments/assets/d6ad131e-e3c0-4d89-97e3-0984934da0e7

Package.swift

@@ -17,7 +17,7 @@ let package = Package(
         ),
     ],
     dependencies: [
-        .package(url: "https://github.com/livekit/client-sdk-swift.git", from: "2.0.14"),
+        .package(url: "https://github.com/livekit/client-sdk-swift.git", from: "2.0.17"),
         .package(url: "https://github.com/apple/swift-docc-plugin.git", from: "1.4.3"),
     ],
     targets: [

Sources/LiveKitComponents/UI/Participant/ParticipantView.swift

@@ -31,11 +31,16 @@ public struct ParticipantView: View {
         GeometryReader { geometry in
             ZStack(alignment: .topLeading) {
                 let cameraReference = TrackReference(participant: _participant, source: .camera)
+                let microphoneReference = TrackReference(participant: _participant, source: .microphone)
 
-                if cameraReference.isResolvable {
+                if let cameraTrack = cameraReference.resolve(), !cameraTrack.isMuted {
                     VideoTrackView(trackReference: cameraReference)
                 } else {
-                    _ui.videoDisabledView(geometry: geometry)
+                    if let microphoneTrack = microphoneReference.resolve(), !microphoneTrack.isMuted, let audioTrack = microphoneTrack.track as? AudioTrack {
+                        BarAudioVisualizer(audioTrack: audioTrack)
+                    } else {
+                        _ui.videoDisabledView(geometry: geometry)
+                    }
                 }
 
                 if _showInformation {

Sources/LiveKitComponents/UI/Visualizer/Visualizer.swift

@@ -0,0 +1,183 @@
+/*
+ * Copyright 2024 LiveKit
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import AVFoundation
+import LiveKit
+import SwiftUI
+
+class AudioProcessor: ObservableObject, AudioRenderer {
+    private weak var _track: AudioTrack?
+    private let isCentered: Bool
+    public let smoothingFactor: Float
+
+    // Normalized to 0.0-1.0 range.
+    @Published var bands: [Float]
+
+    private let _processor: AudioVisualizeProcessor
+
+    init(track: AudioTrack?,
+         bandCount: Int,
+         isCentered: Bool = true,
+         smoothingFactor: Float = 0.3)
+    {
+        self.isCentered = isCentered
+        self.smoothingFactor = smoothingFactor
+        bands = Array(repeating: 0.0, count: bandCount)
+
+        _processor = AudioVisualizeProcessor(bandsCount: bandCount)
+        _track = track
+        _track?.add(audioRenderer: self)
+    }
+
+    deinit {
+        _track?.remove(audioRenderer: self)
+    }
+
+    func render(pcmBuffer: AVAudioPCMBuffer) {
+        let newBands = _processor.process(pcmBuffer: pcmBuffer)
+        guard var newBands else { return }
+
+        // If centering is enabled, rearrange the normalized bands
+        if isCentered {
+            newBands.sort(by: >)
+            newBands = centerBands(newBands)
+        }
+
+        DispatchQueue.main.async { [weak self] in
+            guard let self else { return }
+
+            self.bands = zip(self.bands, newBands).map { old, new in
+                self._smoothTransition(from: old, to: new, factor: self.smoothingFactor)
+            }
+        }
+    }
+
+    // MARK: - Private
+
+    /// Centers the sorted bands by placing higher values in the middle.
+    @inline(__always) private func centerBands(_ sortedBands: [Float]) -> [Float] {
+        var centeredBands = [Float](repeating: 0, count: sortedBands.count)
+        var leftIndex = sortedBands.count / 2
+        var rightIndex = leftIndex
+
+        for (index, value) in sortedBands.enumerated() {
+            if index % 2 == 0 {
+                // Place value to the right
+                centeredBands[rightIndex] = value
+                rightIndex += 1
+            } else {
+                // Place value to the left
+                leftIndex -= 1
+                centeredBands[leftIndex] = value
+            }
+        }
+
+        return centeredBands
+    }
+
+    /// Applies an easing function to smooth the transition.
+    @inline(__always) private func _smoothTransition(from oldValue: Float, to newValue: Float, factor: Float) -> Float {
+        // Calculate the delta change between the old and new value
+        let delta = newValue - oldValue
+        // Apply an ease-in-out cubic easing curve
+        let easedFactor = _easeInOutCubic(t: factor)
+        // Calculate and return the smoothed value
+        return oldValue + delta * easedFactor
+    }
+
+    /// Easing function: ease-in-out cubic
+    @inline(__always) private func _easeInOutCubic(t: Float) -> Float {
+        t < 0.5 ? 4 * t * t * t : 1 - pow(-2 * t + 2, 3) / 2
+    }
+}
+
+/// A SwiftUI view that visualizes audio levels as a series of vertical bars,
+/// responding to real-time audio data processed from an audio track.
+///
+/// `BarAudioVisualizer` displays bars whose heights and opacities dynamically
+/// reflect the magnitude of audio frequencies in real time, creating an
+/// interactive, visual representation of the audio track's spectrum. This
+/// visualizer can be customized in terms of bar count, color, corner radius,
+/// spacing, and whether the bars are centered based on frequency magnitude.
+///
+/// Usage:
+/// ```
+/// let audioTrack: AudioTrack = ...
+/// BarAudioVisualizer(audioTrack: audioTrack)
+/// ```
+///
+/// - Parameters:
+///   - audioTrack: The `AudioTrack` providing audio data to be visualized.
+///   - barColor: The color used to fill each bar, defaulting to white.
+///   - barCount: The number of bars displayed, defaulting to 7.
+///   - barCornerRadius: The corner radius applied to each bar, giving a
+///     rounded appearance. Defaults to 100.
+///   - barSpacingFactor: Determines the spacing between bars as a factor
+///     of view width. Defaults to 0.015.
+///   - isCentered: A Boolean indicating whether higher-decibel bars
+///     should be centered. Defaults to `true`.
+///
+/// Example:
+/// ```
+/// BarAudioVisualizer(audioTrack: audioTrack, barColor: .blue, barCount: 10)
+/// ```
+struct BarAudioVisualizer: View {
+    public let barCount: Int
+    public let barColor: Color
+    public let barCornerRadius: CGFloat
+    public let barSpacingFactor: CGFloat
+    public let isCentered: Bool
+
+    public let audioTrack: AudioTrack
+
+    @StateObject private var audioProcessor: AudioProcessor
+
+    init(audioTrack: AudioTrack,
+         barColor: Color = .white,
+         barCount: Int = 7,
+         barCornerRadius: CGFloat = 100,
+         barSpacingFactor: CGFloat = 0.015,
+         isCentered: Bool = true)
+    {
+        self.audioTrack = audioTrack
+        self.barColor = barColor
+        self.barCount = barCount
+        self.barCornerRadius = barCornerRadius
+        self.barSpacingFactor = barSpacingFactor
+        self.isCentered = isCentered
+
+        _audioProcessor = StateObject(wrappedValue: AudioProcessor(track: audioTrack,
+                                                                   bandCount: barCount,
+                                                                   isCentered: isCentered))
+    }
+
+    var body: some View {
+        GeometryReader { geometry in
+            HStack(alignment: .center, spacing: geometry.size.width * barSpacingFactor) {
+                ForEach(0 ..< audioProcessor.bands.count, id: \.self) { index in
+                    VStack {
+                        Spacer()
+                        RoundedRectangle(cornerRadius: barCornerRadius)
+                            .fill(barColor.opacity(Double(audioProcessor.bands[index])))
+                            .frame(height: CGFloat(audioProcessor.bands[index]) * geometry.size.height)
+                        Spacer()
+                    }
+                }
+            }
+        }
+        .padding()
+    }
+}