The embedded network video server is an embedded device that provides network video transmission and sharing. It is designed and developed for building a high-reliability multimedia digital monitoring system. The digital monitoring system refers to the image captured by the monitoring head through hardware and software. Processed into a digital signal and transmitted to a computer for processing. For the digital monitoring system, according to the different functions of each part of the system, we divide the whole digital monitoring system into seven layers—the presentation layer, the control layer, the processing layer, the transport layer, the execution layer, the support layer, and the acquisition layer. Of course, due to the increasing integration of devices, for some systems, some devices may exist in the system as multiple layers at the same time. The control layer is the core of the entire security monitoring system, which is the clearest embodiment of the system technology level. Usually we have two control methods - analog control and digital control. Analog control is an early control method. The console is usually composed of a controller or an analog control matrix. It is suitable for small local security monitoring systems. This control method has lower cost and lower failure rate. However, for medium and large security monitoring systems, this approach is complicated and does not have any price advantage. At this time, our more sensible choice should be digital control.
1 system composition and working principle
Network video server system, also called digital video encoder, is a professional network transmission device for compressing and processing audio and video data. It consists of audio and video compression codec chip, input and output channel, network interface, audio and video interface, RS485 serial interface. Control, protocol interface control, system software management, etc., mainly to provide video compression or decompression functions, complete image data acquisition or recovery, etc. Currently popular image data compression based on MPEG-4 or H.264 through the Internet Transfer data and processing of audio data. The application of network video server in the current video field is mainly to build a remote monitoring system by using a network video server. The multi-channel digital communication technology based on network video server has many advantages that are not comparable to the traditional analog output system based on video tape recorder. The network video server adopts open software and hardware platform and standard or general interface protocol, and the system has strong expansion capability. It is connected with the future all-digital, networked, systematic, multi-channel resource sharing and other systems.
Figure 1 System block diagram Figure 2 Communication mechanism between AT2042 and CPU
2 video encoding module
At the heart of the video encoding module is the AT2042 from Pentamicro, a dual-channel audio and video codec chip with built-in microcontroller ARM946E that supports video compression encoding for MPEG-4/2/1 and JPEG standards, with picture scaling, Color data format conversion, noise suppression filtering and other functions. The AT2042 interfaces directly to multiple CPUs such as IBM, Motorola, ARM, Xscale and Axis without additional circuitry. The MPC860T controls and accesses the AT2042 through the AT2042's status and command registers and four input and output queues: transmit/receive queues, multiplex/demultiplex queues. The communication mechanism between AT2042 and CPU is shown in Figure 2.
The communication between the AT2042 and the CPU is as follows: the CPU controls the operating state of the built-in microcontroller ARM946E through the command register; the operating status of each FIFO in the AT2042 is checked through the status register; various configuration parameters are sent to the AT2042 through the receive queue, and all The relevant parameters required by the built-in microcontroller ARM946E; the compressed encoded bit stream is read out through the multiplexing queue.
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