| Digital TV is moving forward quickly in China nowadays. PVR-STB which own HDD begins to stride with the coming Olympic Games in Beijing, 2008.This dissertation is research in the special functions about PVR-STB. Specialfically, accomplish two tasks: one is the hard-disk data encryption module and the other is the special playback module. In this subject the STi7109 provided by STMicroelectronics is selected as the embedded decoder main chip and the RTOS ST-OS21 is used as the software environment correspondingly. This dissertation is based on the DVB-S telecast criterion and satellite digital STB system. The author has accomplished the following missions with some creative points:1. The tranditional PVR-STB don't have independent safeguard module to protect digital programme stored in the hard-disk. But this subject provide encryption and decryption for digital programs by software. Elaborate the design principle and process about AES arithmetic in detail, analyze and optimiaze this arithmetic, make it fit in with the emebeded system which own limited resources. In addition, complete performance test in two different platforms: Windows XP and ST-OS21 embedded operation system.2. The tranditional methods for FF/FR is merely extract Intra-Coded Pictures from MPEG-2 stream. In this dissertation, in view of the hard-disk storage mechanism of PVR-STB,the author analyzes the MPEG-2 video/audio stream which is widely used in the region of digital TV broadcast nowadays around the world, accomplish the design procedure about the special playback module and optimize the FF arithmetic. Achieve five kinds of special play functions on the PVR-STB, which including FF, FR, cyclic playback and so on. |
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