If the audio buffer is AVAudioPCMBuffer, it is possible to write it into a file using AVAudioFile's writeFromBuffer:error: method.
How should plain AVAudioBuffer be handled?
In my specific case, I get this buffer from the callback of AVSpeechSynthesizer's writeUtterance:toBufferCallback:
In fact the documentation says:
// Use this method to receive audio buffers that can be used to store or further process synthesized speech.
// The dictionary provided by -[AVSpeechSynthesisVoice audioFileSettings] can be used to create an AVAudioFile.
- (void)writeUtterance:(AVSpeechUtterance *)utterance toBufferCallback:(AVSpeechSynthesizerBufferCallback)bufferCallback API_AVAILABLE(ios(13.0), watchos(6.0), tvos(13.0), macos(10.15)) ;
But I don't know how exactly AVAudioFile can be used if the buffer is not guaranteed to be an AVAudioPCMBuffer.
