A demo program to record audio by iOS service, and transcode the audio to another format.

The feature list

1. Record Audio by AVAudioRecorder class, format includes AAC, PCM, ulaw, alaw, ima4
2. Record Audio by Audio Queue Services, format includes AAC, PCM, ulaw, alaw
3. Record Audio by Audio Unit Services, format includes PCM
4. Record Audio by Audio Graph Services, format includes PCM
5. Covert audio format by AudioConverter, PCM to AAC
6. Covert audio format by FFmpeg, PCM to AAC
7. Play Audio by AVAudioPlayer
8. Play Audio by Audio Queue
9. Play Audio by Audio Unit
10. Mix Audio by Audio Unit