苹果airplay协议中音频协议airtunes客户端的实现。通过RTP传输音频流，通过RTSP对音频流进行控制，音频的decode支持mp3,aac,alac格式。-Achieve airtunes protocol in apple airplay protocol. Through the RTP transfer audio stream, through RTSP control on the audio stream, audio decode supports MP3, AAC,