IP high-definition cameras have ingeniously surpassed the traditional analog cameras. Nowadays, high-definition surveillance cameras on the market have formed a diversified product pattern based on megapixels with 2 million pixels and 3 million pixels. An IP HD network camera is mainly composed of video capture, video encoding, and network transmission. An IP HD camera can be seen as a combination of a HD camera and a computer. It performs progressive scans through CMOS/CCD photoreceptors, enabling optical signals to be captured directly and processed on a single SoC chip for direct transmission over an IP network, enabling users to access local or remote locations over a standard IP-based network infrastructure. Enables viewing, storage, and management of high-definition video data.
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IP HD cameras are classified by the image sensor (ImageSensor) of the core components, and are mainly CCD and CMOS. Among them, CMOS is subdivided into traditional CMOS and Exmor CMOS or back-illuminated CMOS. The basic structure and working principle of CCD and CMOS are as follows:
CCD is the abbreviation of ChargeCoupledDevice (charge coupled device), which is a semiconductor imaging device. The charge information stored by the CCD charge coupler needs to be read bit by bit after the synchronization signal control, charge information transfer and read. The output needs to have a clock control circuit and three different sets of power supplies. The whole circuit is more complicated.
CMOS is the abbreviation of ComplementaryMetal-OxideSemiconductor. Like CCD, it is the semiconductor that can record light changes in HD cameras. CMOS photoelectric sensors directly generate current (or voltage) signals after photoelectric conversion, and signal reading Very simple, the characteristics of the two are as follows.
The CCD charge coupler needs to output information one bit at a time in the behavior unit under the control of the synchronous clock, and the speed is slow;
The CMOS photoelectric sensor can take out the electrical signal while collecting the optical signal, and can simultaneously process the image information of each unit, which is much faster than the CCD charge coupler;
Most of the CCD charge couplers need three sets of power supply, which consumes a lot of power;
CMOS photosensors use only one power supply and consume very little power. CMOS photosensors have great advantages in terms of energy saving.
The "brain" of IP HD cameras: core processing chip
There are many design schemes for HD IPC, but from the architectural point of view, there are mainly two types: First, CCD/CMOS sensors are used as image acquisition devices, and SoC chips for image processing and encoding functions are provided; second, front-end camera modules are used. , as an image acquisition device, and a general-purpose ASIC or DSP for encoding and transmission. Due to the flexibility of the first architecture design, it is widely adopted by manufacturers.
There are three implementation schemes in image processing: the first scheme uses a dedicated ISP processing chip and encoding processing part, which is more flexible, uses a dedicated ISP chip with good stability, can guarantee image quality; the second scheme adopts integration ISP's coding chip, the flexibility of this scheme is second to the first scheme, and the stability of the dedicated ISP processing chip is high, but the image quality is generally high and the cost is high; the third scheme uses FPGA and other chips to realize signal processing and coding functions. The program is the most flexible, but the stability is poor, the cost is the highest, and the image quality is difficult to guarantee. The dedicated ISP solution is flexible in design, cost-effective, and can guarantee the quality of images. It is suitable for HD IPC design.
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