Audio and Video Decoding and Synchronous Playback for Embedded Systems

The audio and video decoding and synchronization playback system ofMPEG-2 TS stream is designed and implemented based on ARM embedded system. In this system, hardware processor is embedded in the ARM processor. In order to make full use of this resource, hardware MFC is adopted. The multi-format codec decoder decodes the video data and decodes the audio data using the open source Mad (libmad) library. The V4L2 (Video for Linux2) driver interface and the ALSA (advanced Linux sound architecture) library are used to implement the video. Because the video frame playback period and the hardware processing delay are inconsistent, the system has a time difference between the audio and video data operations, which causes the audio and video playback to be out of sync. Therefore, we use the method of synchronizing the video playback implemented to the audio playback stream; realize the audio and video are playing sync. Test results show that, the designed audio decodes and synchronization playback system can decode and synchronize audio and video data.

Development of a Digitized Medium Frequency Electronic Therapeutic Instrument

In the process of physical therapy, it is usual to stimulate nerves or muscles of body with electrical signals through the electrodes, such as changeable square waves or sine waves, to control the corresponding functions or the action of muscular dilatation so as to relieve the pain of patients. On the basis of recent medical research, bell-like wave and exponential wave are most suitable for use. A digitalized medium frequency electronic therapeutic instrument based on the ARM embedded system is developed. The discrete bell-like wave and exponential wave are generated through the S3C2410 microprocessor, and then the digital signal is converted into analog signal through D/A converting chip. Finally the analog signal is amplified and output through power amplifying and isolated output circuit to generate the curing wave for human body. This method solved the difficulty of generating bell-like curing wave in traditional analog medium frequency electronic curing instrument.