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The Development Of A Million Hd Webcams.
Apr 17, 2018

With the wide application of IP technology and multimedia technology, millions of high-definition webcams have developed rapidly. In the network video conference and network monitoring field, the traditional video signal is converted into the digital video signal, and the transmission of the existing IP network has become the mainstream of today. Technically speaking, it is generally used to realize remote monitoring by using webcam. Currently, there are two types of network monitoring cameras in the market: 1 class is composed of ordinary camera and video conversion server, which is bulky and cumbersome to operate. The other category is to integrate all network access functions into the monitoring camera, which is small, functional, easy to use and maintain. There are many solutions for the integrated multi-million hd webcams, and a design scheme based on embedded DSP is proposed for your reference:

1. Embedded processor TMS320DM642.

DM462 for short, is the TI company recently released a new generation of multimedia processor, it is based on the second generation of high-performance VelociTI VLIW structure, is applicable to a variety of digital media application. DM642 clock frequency is 600 MHZ, instructions to speed up to 4800 MIPS. The DSP two features: one is with three configurable video interface (VP), can be collected three video signals at the same time; Also integrates the Ethernet interface, 10/100 MBPS mode adaptive, able to work in full duplex or half duplex mode, and has the hardware flow control and ensure the quality of service (QoS) support. The function of DM642 is very strong, it is one of the best platform of multimedia communication system.

2. Overall architecture of network camera hardware.

The hardware platform of the whole system consists of 6 parts: a video collection, b data storage, c video processing, d video display, e network, e power management. Cameras, video collection part adopts simulation PAL with high-precision video A/D converter to get digital image. A/D converter adopts TVP5145 chip of TI company, the sampling accuracy reached 10 bit, support and BT656 CCIR - 656 output format. Data storage part of RAM used samsung SDRAM. 64 to tie in with DM642 EMIF, using four pieces of SDRAM, every piece of work in 16 bit mode, single chip capacity of 32 MB. Data storage type of ROM using ATMEL company NOR Flash chips, total capacity of 256 KB, data bus for eight. The SDRAM in this system is used to hold the code of the system runtime and the temporary image data. Flash is used to save the system's self-starting code and system program code. Video display part adopts digital LCD, which can save the number/mode conversion chip, and only one CPLD drive LCD.CPLD adopts Altera's MAX3000 series. As an auxiliary function, this part can be selected according to the actual application. The Ethernet controller (i.e., EMAC) of DM642 belongs to the data link layer, so the network communication can be carried out by external physical layer chip. Here, Intel's LXT971A chip, which provides the MII interface, can easily connect to DM642. The power management part plays an important role in the design of a hardware system. The power module of this system adopts MAXIM's solution, including a MAX1762 chip.

TI company developed a two-layer device driver model for DM642 VP. The upper Driver is called Class Driver, closer to the underlying hardware. Just write the driver for this model. For Ethernet ports, TI provides a network development component that provides a platform for developing web applications on DSP. With this platform in the development of network applications, need not too much to consider how the data enclosed into IP packet, also need not too much concerned about the inside of the TCP/IP protocol work mechanism, it can shorten product development cycle and time to market.

The two-layer device driver model is shown in figure 2. The top layer is the application, and the bottom layer is the underlying hardware, including the DM642 VP and video A/D chips. The middle braces are partly the device drivers. There is also a chip support library, which provides the C language interface on the configuration and control chip.

According to the characteristics of VP, each layer of the two-layer drive model driven by the device is divided into two layers. As can be seen from figure 2, the Class Driver is divided into FVID Class Driver and GIO Class Driver. The former is closer to the application, and it provides some API functions that are especially suitable for images. Which provides with the Mini Driver communicate API function. The Mini Driver into general parts and special parts, the advantage of this is that when change the hardware without having to rewrite the Mini Driver, only need to modify specific parts, improve the repeated use of the code.

The core of the network development component is a series of TCP/IP stack libraries. Includes: a stack library and network tool library, it contains some optimized compiled protocol stack code; B operating system adaptive library, which coordinates the interface between TCP/IP protocol stack and DSP/BIOS; C network control and scheduling library, which determines the initialization of the TCP/IP environment and how the network related events are scheduled; D multiple hardware abstraction layer platform library provides support for TI company's multiple development board. With the development of technology, millions of high-definition webcams will become clearer and more intelligent.