TTS

• Extend Speech Synthesis with personal and custom voices

  https://developer.apple.com/videos/play/wwdc2023/10033/

• Creating an audio unit extension

  https://developer.apple.com/documentation/avfaudio/audio_engine/audio_units/creating_an_audio_unit_extension

  It describes how to set a parameter from the host app

• https://appmakers.dev/bcp-47-language-codes-list/

xcode, create project, select ios or macos, select Audio Unit Extension App

1. Product name: sherpa-onnx-tts

2. Team: None

3. Organization identifier: org.k2-fsa

4. Organization name: Next-gen Kaldi

5. Audio unit type: Speech synthesizer

6. Subtype code: k2k2

7. Manufacturer code: k2k2

8. User interface: No user interface

9. Include tests: Don't check it

example:

public override var internalRenderBlock: AUInternalRenderBlock {
       return { [weak self]
           actionFlags, timestamp, frameCount, outputBusNumber, outputAudioBufferList, _, _ in
           guard let self else { return kAudio_ParamError }

           // This is the audio buffer we are going to fill up
           var unsafeBuffer = UnsafeMutableAudioBufferListPointer(outputAudioBufferList)[0]
           let frames = unsafeBuffer.mData!.assumingMemoryBound(to: Float32.self)

           var sourceBuffer = UnsafeMutableAudioBufferListPointer(self.currentBuffer!.mutableAudioBufferList)[0]
           let sourceFrames = sourceBuffer.mData!.assumingMemoryBound(to: Float32.self)

           for frame in 0..<frameCount {
               if frames.count > frame && sourceFrames.count > self.framePosition {
                   frames[Int(frame)] = sourceFrames[Int(self.framePosition)]
                   self.framePosition += 1
                   if self.framePosition >= self.currentBuffer!.frameLength {
                       break
                   }
               }
           }

           return noErr
       }