Design And Implementation Of Networking Building Visual Door Bell System

As a modern building management department, it’s very necessary to provide two-wayvisual call service for visitors and residents to make households through the dualidentification of the image and voice confirm the identity of visitors, to ensure the safety ofbuilding management and residents’ property and to improve the management and servicelevel, it’s also one direction of the modern residential equipment. So in this paper, theresearch and implementation of the visual doorbell system has certain engineeringsignificance and application value.Based on analysis of the building talkback system development and present situation, inview of that the present general traditional video door phone systems based on analog audioand video signal with low rate of data control signal, have larger workload in systemdebugging and maintenance, worse anti-interference ability in transmission aspects, seriousattenuation, and have problems such as signal quality greatly reduced and channel occupiedin medium and large community with more users, proposes the building visual doorbellsystem realization scheme based on TCP/IP. The scheme will no longer use common PCkernel board as the client, but use the S3C2440embedded CPU as the core processor todesign the doorbell system, which has advantages of low cost, small volume. In view of that,the past monitoring systems to the PC as a client have huge volume, high cost, put forward anembedded the doorbell system based on S3C2440hardware platform; In view of existing thedoorbell systems function single, not very intelligent, puts forward an open source, goodstability, cutting and custom and portability strong Linux operating system as the softwareplatform of this system.In the video image acquisition aspect, this paper chooses V4L2, the improved version ofV4L as the image acquisition standard.in order to overcome the problem that the directnetwork transmission video image takes more network bandwidth, this paper introduces thevideo image compression processing. Considering the compression effect, decodingcomplexity, embedded processor affordability and power consumption, etc, this paperchooses MJPEG standard as the image compression codec.In the audio compression codec aspect, considering the bit rate, voice quality, complexity and delay etc ensemble factor, finally chooses G.726standard as audio codec.In the network transmission protocol aspect, due to the fact that the transport layer of theTCP protocol has higher reliability but poor real-time performance, while UDP has betterreal-time but poor reliability, puts forward the way of using UDP protocol in the transportlayer combined with real-time transmission protocol and real-time transmission controlprotocol in application layer for audio and video data transmission.In human-computer interaction aspect, based on the comprehensive consideration fromcost and development mode and so on, compared several common graphic interfaces, andfinally chose the graphics interface based on GTK+DirectFB.The design of networking visual doorbell system presented in this paper has beenrealised in ARM9platform (S3C2440), the actual system has passed the performance test, theoperation effect is good, and the indicators have reached the design requirements.