How is it possible to wait for speech to buffer to complete inline before proceeding?
I have a function that writes speech to a buffer, then resamples and manipulates the output, then included in an AVAudioengine workflow, where speech is done in faster than real-time.
func createSpeechToBuffer( stringToSpeak: String, sampleRate: Float) -> AVAudioPCMBuffer?
{
var outBuffer : AVAudioPCMBuffer? = nil
let utterance = AVSpeechUtterance(string: stringToSpeak)
var speechIsBusy = true
utterance.voice = AVSpeechSynthesisVoice(language: "en-us")
_speechSynth.write(utterance) { (buffer: AVAudioBuffer) in
guard let pcmBuffer = buffer as? AVAudioPCMBuffer else {
fatalError("unknown buffer type: \(buffer)")
}
if ( pcmBuffer.frameLength == 0 ) {
print("buffer is empty")
} else {
print("buffer has content \(buffer)")
}
outBuffer = self.resampleBuffer( inSource: pcmBuffer, newSampleRate: sampleRate)
speechIsBusy = false
}
// wait for completion of func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance)
while ( _speechSynth.isSpeaking )
{
/* arbitrary task waiting for write to complete */
}
while ( speechIsBusy )
{
/* arbitrary task waiting for write to complete */
}
return outBuffer
}
After I wrote the method and it failed to produce the desired output (inline), I realized that it returns before getting the results of the resampling. The callback is escaping, so the initial AVAudioBuffer from the callback will return after createSpeechToBuffer has completed. The resampling does work, however I currently must save the result and continue after being notified by the delegate "didFinish utterance" to proceed.
func write(_ utterance: AVSpeechUtterance, toBufferCallback bufferCallback: @escaping AVSpeechSynthesizer.BufferCallback)
Attempts at waiting for _speechSynth.isSpeaking or the speechIsBusy flag are not working and a dispatch queue or semaphore are blocking the write method from completing.
How is it possible to wait for the result inline versus recreating a workflow depending on the delegate "didFinish utterance"?
on macOS 11.4 (Big Sur)
