Audio/Video Transporation Over IP And Codec Technology Research, Based On Linux And DSP Technology

While embedded system is widely used today, the interconnection betweenembedded systems and Internet is becoming more and more important. The hardwareimprovement has made it common that an embedded system has a high performanceMCU(such as ARM) or a DSP(such as TI, ADI or Equator) as its main controller. Thememory configuration is significantly increased to 16MB-64MB which enables anembedded system to run comparatively complex software such as Embedded Linux,VxWorks, etc.This thesis introduces a complete embedded system solution, including DSP chipdescription, system architecture, video/audio interface, device driver, cross-compile,porting of Linux and it's boot, and the applications.In hardware, the introduction to DSP consists of 2 parts. One is VLIW(Very LongInstruction Word) architecture that is very popular in modern DSP design. As thecompiler technology is very important to use VLIW's parallelism so that compilertechnology is also briefly introduced. The other part is peripherals. Only a highthroughput can guarantee the real-time acquisition of video signals. So, not only thecomputing ability but also the transmission speed over I/O ports of a DSP chip is amain concern when selecting DSP chips.3 aspects are introduced in detail in software introduction. The first is theestablishment of cross-compile environment and how to use a PC to develop Linuxsoftware running on target DSP. The second is device drivers in Linux. All hardwares,such as video input chip, can be used by software only after they're abstracted to"devices". This technology is called "kernel modules". All such modules run in kernelspace. The third part is the main body of this thesis that describes how to implement anetwork multi-media device on the basis of hardware and software mentioned above.My experiments testified that on the encoder side of the multi-media device, the DSPrunning at 351MHz has the processing ability to encode half-D1 video in real time(Full motion, 30fps) with MPEG4 format, and transmit compressed packets by RTP.At the same time, the DSP can capture and transmit PCM audio. The decoder side canreceive, decode and playback video/audio stream simultaneously. Meanwhile, preciseacquisition, transmission and receiving ensure the synchronization between video andaudio. Network transmission uses RTP protocol to insure real time effects of videoand audio and ensure different decoder devices receive the same video/audio streamin multicast mode.