| As a kind of new PA system (public address system), the digital audio broadcast system based on Ethernet has more advantages than the traditional PA system and vast market and developing prospect, not only it can play the sound in real time, but also it can play the sound in global field and regional field.Firstly, the design proposal of the system is determined in this thesis, the function requirements of the server and terminal of the system are analyzed in detail, the key technologies in the process of designing and realizing are discussed. Secondly, the overview flow and the function of each pint of the server and terminal are designed according to the function demands of the system. Again, the process of realizing the function of each part of the server and terminal based on the design of the system is analyzed in detail. The whole design process includes acquisitioning digital audio data on the PC with double-buffer technology; Segmenting the digital audio data and encapsulating them as special structure of voice packets; Delivering the digital audio data as IP unicast or broadcast packets to the terminal unit; Storing the digital audio data in a WAV file; Storing the IP address and the geographicposition of the terminal in the server of the system. Receiving and storing the digital audio data in the terminal unit EasyARM8962; Transmiting the digital audio data between the EasyARM8962 and the audio decode chip VS1003; Converting the digital audio data to analog signals in the VS1003 and broadcasting; Judging the special structure of voice packets by the system terminal to realize the regional broadcasting.All the functional parameters of the basic performance and the real-time performance of the system are tested and analyzed in the last. The test for the digital audio broadcast system based on Ethernet validates the design and indicate that the audio data can be broadcasted in time to all the terminal units or parts of them at the same time. |
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