Hi There,
Whenever I want to use the microphone for my ShazamKit app while connected to AirPods my app crashes with a "Invalid input sample rate." message.
I've tried multiple formats but keep getting this crash. Any pointers would be really helpful.
func configureAudioEngine() {
do {
try audioSession.setCategory(.playAndRecord, options: [.mixWithOthers, .defaultToSpeaker, .allowAirPlay, .allowBluetoothA2DP ,.allowBluetooth])
try audioSession.setActive(false, options: .notifyOthersOnDeactivation)
} catch {
print(error.localizedDescription)
}
guard let engine = audioEngine else { return }
let inputNode = engine.inputNode
let inputNodeFormat = inputNode.inputFormat(forBus: 0)
let audioFormat = AVAudioFormat(
standardFormatWithSampleRate: inputNodeFormat.sampleRate,
channels: 1
)
// Install a "tap" in the audio engine's input so that we can send buffers from the microphone to the signature generator.
engine.inputNode.installTap(onBus: 0, bufferSize: 1024, format: audioFormat) { buffer, audioTime in
self.addAudio(buffer: buffer, audioTime: audioTime)
}
}
```
Following up with the AVFAudio team on this, the recommended approach is to convert the buffer inside the installTap function into a buffer with a AVAudioFormat that's accepted by ShazamKit. Here's a sample code how that conversion could look like.
Configure AVAudioEngine
You need to configure the audio engine to use the input node of the HW and install a tap on that. Inside the installTap function, convert the buffer into a buffer with the desired audio format.
func configureAudioEngine() {
guard let outputAudioFormat = AVAudioFormat(standardFormatWithSampleRate: 44100, channels: 1) else { return }
let inputNode = audioEngine.inputNode
let inputFormat = inputNode.inputFormat(forBus: 0)
inputNode.installTap(onBus: 0, bufferSize: 2048, format: inputFormat) { [weak self] buffer, audioTime in
guard let self = self else { return }
// convert the buffer into the desired format
if let outputBuffer = self.convert(inputBuffer: buffer, outputFormat: outputAudioFormat) {
// use the converted buffer, AVAudioTime needs to be mapped in order to use it
self.session.matchStreamingBuffer(outputBuffer, at: nil)
}
}
}
Convert AVAudioPCMBuffer
Convert the AVAudioPCMBuffer using the desired AVAudioFormat and return the new buffer.
func convert(inputBuffer: AVAudioPCMBuffer, outputFormat: AVAudioFormat) -> AVAudioPCMBuffer? {
let outputFrameCapacity = AVAudioFrameCount(
round(Double(inputBuffer.frameLength) * (outputFormat.sampleRate / inputBuffer.format.sampleRate))
)
guard let outputBuffer = AVAudioPCMBuffer(pcmFormat: outputFormat, frameCapacity: outputFrameCapacity) else { return nil }
guard let converter = AVAudioConverter(from: inputBuffer.format, to: outputFormat) else { return nil }
converter.convert(to: outputBuffer, error: nil) { packetCount, status in
status.pointee = .haveData
return inputBuffer
}
return outputBuffer
}
Final Steps
Set the AVAudioSession category to the desired options and check for microphone permission, then you can start the AVAudioEngine. Finally listen for results on SHSession.
try AVAudioSession.sharedInstance().setCategory(.playAndRecord, options: [.mixWithOthers, .defaultToSpeaker, .allowAirPlay, .allowBluetoothA2DP])
AVAudioSession.sharedInstance().requestRecordPermission { [weak self] success in
guard success, let self = self else { return }
Task.detached { try? self.audioEngine.start() }
}
Task { @MainActor in
for await case .match(let match) in session.results {
self.matchResult = match.matchResult
}
}
