Webcam based on ML86500 design (1)

1 Introduction

In recent years, as digital image processing, multimedia technology, embedded system hardware and the rapid development of technology and broadband network constantly popular, video surveillance has gradually come to people's lives.

And compared with traditional analog monitor, IP video surveillance to overcome the limitations of analog CCTV monitor: first of all, digital video can computer networks (LAN or WAN) on the transmission of image data, basically no distance limitation, signal vulnerable to interference, may significantly improve image quality and stability; secondly, digital video using existing computer Internet, no duplicate wiring, installation is flexible; finally, digital storage, compressed video data can be stored directly to inquire about the simple and fast.

At present, the network camera programme most used CPU + DSP CPU combo, complete control, communications, and other functions, and DSP is mainly complete audio and video encoding process, but such programs are generally more expensive.

This article is designed for the network camera based ML86500 programmes with a high compression ratio, low bandwidth, high image quality and low cost.

2 system hardware design

2.1 hardware overall programme

Webcam hardware overall scheme as shown in Figure 1.

The basic principles of network cameras: CCD sensor light into electrical charge, and output CVBS analog video signals to video decoding chip (TW9910); video decoding chip will CVBS analog video signal-to-digital conversion (A/D) into a YUV 4: 2: 2 format of digital signal and output to video coding chip — ML86500; ML86500 be encoded video information, generate MPEG4 compression; MPEG4 stream after stream of RTP Protocol package through network is sent to the remote client (PC), a remote client to decode the video information is restored.

2.2 MPEG4 real-time encoder circuit

ML86500 is OKI company development of real time MPEG4 video compression (coding) with single-chip products, the chip was OKI flexibly and dedicated Accelerator original algorithm, low-cost realized superior design goal is for surveillance cameras, webcams and other video surveillance equipment.

Therefore this network camera programme selection of video coding chip ML86500.

ML86500 internal principle is shown in Figure 2.

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