🐞 Fix buffer method, layout and update README.md

🐞 Bugs

The controlProminence method is now deprecated. Therefore, I removed the deprecated code and updated the button style to be borderedProminent instead of bordered.

The match button does not have padding and touches the bottom edge of the screen. Therefore, I added vertical padding to it.

The old buffer method would make the session fail to find a match for the audio. Therefore, I updated the buffer and signature methods per the developer documentation (https://developer.apple.com/documentation/shazamkit/shsignaturegenerator/generating_a_signature_from_an_audio_buffer).

📄 Documentation

iOS 15.0 and Xcode 13.0 are officially out of beta. Therefore, I removed any mention of the word "beta" in the README.md file.

The README.md file does not contain a screenshot similar to other repositories from the organisation. Therefore, I added a screenshot.

README.md

@@ -4,9 +4,9 @@ This demo project is associated with my article [ShazamKit: A first look](https:
 
 ### Availability
 
-iOS 15.0+ (Beta)
+iOS 15.0+
 <br>
-Xcode 13.0+ (Beta)
+Xcode 13.0+
 
 ### Frameworks
 
@@ -15,3 +15,7 @@ Foundation
 ShazamKit
 <br>
 SwiftUI
+
+<br>
+
+<img src="https://user-images.githubusercontent.com/34966652/140640986-a54461da-7a9c-4c09-b57e-9d3f6c39a5a3.jpeg" height="640" alt="Preview"/>

Shared/ViewModels/ContentViewModel.swift

@@ -42,18 +42,40 @@ class ContentViewModel: NSObject, ObservableObject {
 
     //MARK:- Private Methods
 
-    private func buffer() -> AVAudioPCMBuffer? {
-        guard let audioFileURL = audioFileURL,
-              let audioFile = try? AVAudioFile(forReading: audioFileURL) else { return nil }
-        let pcmFormat = audioFile.processingFormat
-        let frameCapacity = AVAudioFrameCount(12 * audioFile.fileFormat.sampleRate)
-        guard let buffer = AVAudioPCMBuffer(pcmFormat: pcmFormat, frameCapacity: frameCapacity) else { return nil }
-        try? audioFile.read(into: buffer)
-        return buffer
+    private func buffer(audioFile: AVAudioFile, outputFormat: AVAudioFormat) -> AVAudioPCMBuffer? {
+        let frameCount = AVAudioFrameCount((1024 * 64) / (audioFile.processingFormat.streamDescription.pointee.mBytesPerFrame))
+        let outputFrameCapacity = AVAudioFrameCount(12 * audioFile.fileFormat.sampleRate)
+        guard let inputBuffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat, frameCapacity: frameCount),
+              let outputBuffer = AVAudioPCMBuffer(pcmFormat: outputFormat, frameCapacity: outputFrameCapacity),
+              let converter = AVAudioConverter(from: audioFile.processingFormat, to: outputFormat) else { return nil }
+        while true {
+            let status = converter.convert(to: outputBuffer, error: nil) { inNumPackets, outStatus in
+                do {
+                    try audioFile.read(into: inputBuffer)
+                    outStatus.pointee = .haveData
+                    return inputBuffer
+                } catch {
+                    if audioFile.framePosition >= audioFile.length {
+                        outStatus.pointee = .endOfStream
+                        return nil
+                    } else {
+                        outStatus.pointee = .noDataNow
+                        return nil
+                    }
+                }
+            }
+            switch status {
+            case .endOfStream, .error: return nil
+            default: return outputBuffer
+            }
+        }
     }
 
     private func signature() -> SHSignature? {
-        guard let buffer = buffer() else { return nil }
+        guard let audioFileURL = audioFileURL,
+              let audioFile = try? AVAudioFile(forReading: audioFileURL),
+              let audioFormat = AVAudioFormat(standardFormatWithSampleRate: 44100, channels: 1),
+              let buffer = buffer(audioFile: audioFile, outputFormat: audioFormat) else { return nil }
         let signatureGenerator = SHSignatureGenerator()
         try? signatureGenerator.append(buffer, at: nil)
         return signatureGenerator.signature()

Shared/Views/ContentView.swift

@@ -56,9 +56,9 @@ struct ContentView: View {
                 .padding(.vertical)
             Button(viewModel.isMatching ? "Matching…" : "Match preexisting audio", action: viewModel.startMatching)
                 .disabled(viewModel.isMatching)
+                .padding(.vertical)
         }
-        .buttonStyle(.bordered)
-        .controlProminence(.increased)
+        .buttonStyle(.borderedProminent)
         .controlSize(.large)
         .tint(.blue)
     }