| Nowadays, digital television applications and the video monitoring develop fast. At the same time, the streaming media has gradually become the main way of media transmission in the Internet. Terrestrial digital television signal covers a wide range in our country, and there have been special receiver for it. But people don’t buy a specific receiver only for watching terrestrial television. And terrestrial television signal can’t be received by smart phones. This paper designed a multimedia gateway system, based on which smart phone can receive terrestrial digital television signal freely. In addition, considering that video monitoring play a more and more important role in many occasions such as subway, supermarket and home, the function of video monitoring is added to gateway system in the paper.The architecture of gateway system in the paper is composed of hardware and software. The part of hardware includes tuner, modem, camera, arm system, and Wi-Fi router. The part of software has the function of digital television transmission and video monitoring. This part includes some key technology, such as demuxer, stream distribution, multithreading response, data capture, data compression and Streaming media transmission.Digital television retransmission module of gateway system implements retransmitting terrestrial digital television signals for smart phone. First of all, based on the research of the characteristics of transport stream, paper puts forward the idea of adopting transport stream as the main form of data transmission. The design uses digital TV tuner to transform radio frequency signal to transport stream which include multi-channel video data. The multi-channel video data transmit to streaming media server. The second, the streaming media server is set up through open source of Live555, to build a streaming data connection between gateway system and phone terminal. So that the transport stream could be retransmit through LAN based on RTSP protocol. Finally, the local area network is set up by WI-FI router, to distribute the stream, so that the phone terminal in the LAN could receive the video data.The paper also researched the technology of network real-time monitoring, and proposed the idea of extending the video monitoring function on the gateway system. Paper called the V4L2 interface in Linux system to control the camera to capture the original YUV video data. Then for reducing the video data storage of gateway system and saving network bandwidth, paper adopts the popular x264 encoder to compress the original YUV video data. The effect of compression reaches 500 times. At last, to achieve the effect of real-time transmission, paper joined the pipeline blocking control in data transmission, so that client terminal could read the video data from gateway system synchronously.The multimedia gateway system combines the function of digital television signal retransmission and video monitoring innovatively. This solution has the advantages of small volume, real-time transmission, free transmission, and saving bandwidth. Finally, paper made a summary for the system and discussed future work. |
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