Network Camera (IPC) is a new generation of cameras combined with traditional camera and network technology. It can transmit images to the other end of the globe through the network, and remote browsers do not need any professional software, as long as the standard network The browser (such as "MicrosoftIE or Netscape" can monitor its image. The network camera (IPC) has an embedded chip embedded in the real-time operating system. The video signal transmitted by the camera is digitized and compressed by the high-efficiency compression chip through the network bus. Transfer to the web server. Users on the network can view the camera image on the web server directly with the browser, and the authorized user can also control the action of the camera pan/tilt lens or operate the system configuration.
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Image compression method
For network cameras, image compression methods mainly include:
JPEG, MJPEGMPEG1, MPEG2
MPEG4H.264H.264
What is H.264?
H.264 is a high performance video codec technology. At present, there are two organizations that have developed video codec technology in the world. One is “ITU (ITU-T)â€, which has standards such as H.261, H.263, H.263+, etc. The other is “ The International Organization for Standardization (ISO) has established standards such as MPEG-1, MPEG-2, MPEG-4, and so on. H.264 is a new digital video coding standard jointly developed by the Joint Video Group (JVT) jointly organized by two organizations, so it is both ITU-T H.264 and ISO/IEC MPEG-4 advanced video. Encoding (Advanced Video Coding, AVC), and it will become the 10th part of the MPEG-4 standard. Therefore, whether it is MPEG-4 AVC, MPEG-4 Part 10, or ISO/IEC 14496-10, it means H.264.
The biggest advantage of H.264 is that it has a high data compression ratio. Under the same image quality, the compression ratio of H.264 is more than twice that of MPEG-2, which is 1.5 to 2 times that of MPEG-4. For example, if the size of the original file is 88GB, it will be 3.5GB compressed by the MPEG-2 compression standard, and the compression ratio will be 25:1. After compression by the H.264 compression standard, it will become 879MB, from 88GB to 879MB. The compression ratio of H.264 reaches an amazing 102:1! Why does H.264 have such a high compression ratio? The low bit rate (LowBitRate) plays an important role, compared with compression technologies such as MPEG-2 and MPEG-4ASP. H.264 compression technology will greatly save users' download time and data traffic charges. In particular, H.264 has a high compression ratio and high quality and smooth images.
MPEG-4
Compared with MPEG-1 and MPEG-2, MPEG-4 is characterized by its more suitable for interactive AV services and remote monitoring. MPEG-4 is the first dynamic image standard that takes you from passive to active (no longer just watching, allowing you to join, that is, interactivity). Another feature is its comprehensiveness. From the root, MPEG-4 attempts to combine natural objects with artificial objects (in the sense of visual effects). The design goals of MPEG-4 are also more adaptable and more flexible.
MJPEG
The full name is "MotionJointPhotographicExpertsGroup", which is a video encoding format.
MotionJPEG technology "translates" analog video signals from TV cameras with closed circuits into video streams and stores them on the hard disk.
Typical applications are digital video recorders and the like. Unlike MPEG, MJPEG does not use interframe coding, so it is easy to edit with a non-linear editor. MJPEG's compression algorithm is in line with MPEG. It is very powerful and can send high quality images and generate full animation video. Correspondingly, MJPEG has a high bandwidth requirement, which is equivalent to T-1. MJPEG information is a huge object stored in digital media, which requires a large amount of storage space to meet the needs of most users today. So from another perspective, under certain conditions, MJPEG is perhaps one of the least efficient encoder/decoders.
MJPEG is a 24-bit "true-color" image standard. MJPEG works to convert RGB format images into YCrCB format. The purpose is to reduce the file size, which is about 1/3~1/2.
The difference between MJPEG and MJPG
MJPG is an abbreviation for MJPEG, but MJPEG can also represent file format extensions.
D1
At present, the monitoring industry mainly uses several resolutions such as Qcif (176×144), CIF (352×288), HALFD1 (704×288), and D1 (704×576).
D1 is a high-definition image format with a resolution of 720*576. In order to save trouble, some people simply call 4CIF (704*288) also D1. And this is already the industry and user default. So in the industry, it is not important that a product's D1 is 720*576 or 704*576. At present, only the video server and network camera on the way can experience the clear effect of D1. Although D1 is already very clear, there are still many people who are still not satisfied with the D1 effect, so as other members of the D1 family are also entering the stage of monitoring, here we will introduce several members of the D1 family:
D1: 480i format (525i): 720 × 480 (horizontal 480 lines, interlaced), the same as NTSC analog TV, the line frequency is 15.25kHz, equivalent to what we call 4CIF (720 × 576)
D2: 480P format (525p): 720 × 480 (horizontal 480 lines, progressive scan), much clearer than D1 interlaced scanning, and the same as the progressive scan DVD, the line frequency is 31.5kHz
D3: 1080i format (1125i): 1920×1080 (horizontal 1080 line, interlaced), HD resolution uses the most resolution, the resolution is 1920×1080i/60Hz, and the horizontal frequency is 33.75kHz.
D4: 720p format (750p): 1280 × 720 (horizontal 720 lines, progressive scan), although the resolution is lower than D3, but because of progressive scanning, more people on the market feel relative to 1080I (actually 540 lines) The visual effect is clearer. However, personally speaking, in the case of the maximum resolution of 1920×1080, D3 feels more clear than D4, especially in terms of text performance, the resolution is 1280×720p/60Hz, and the line frequency is 45kHz.
D5: 1080p format (1125p): 1920×1080 (horizontal 1080 line, progressive scan), the highest standard for civilian HD video, the resolution is 1920×1080P/60Hz, and the line frequency is 67.5KHZ.
The D1 and D2 standards are the highest standards of our general analog TV, and can not be called high definition. The 1080i standard of D3 is the basic standard of high definition TV, it can be compatible with 720p format, and D5 1080P is only a professional standard. It is not a civilian level. The 60HZ given above is only the ideal field frequency, and its line frequency is 67.5KHZ. At present, there is no TV with such high line frequency. Actually, the field frequency of 1080P is only in the professional field. 24HZ, 25HZ and 30HZ.
CPU
The CPU is the central processor, which is one of the core components of the network camera. It is the brain of the network camera. Most of the data information is done by it. The speed of its work directly affects the speed of the camera. CPU can be divided into control unit (ControlUnit; CU), logic unit (ArithmeticLogicUnit; ALU), storage unit (MemoryUnit; MU) three parts, from the application point of view can be divided into X86 type, embedded and other high performance three categories . Network cameras generally use embedded CPUs.
FlashMemory
FlashMemory is a flash memory that retains stored data information in the event of a power outage, but data deletion is not in a single byte but in a fixed block. The block size is generally from 256KB to 20MB. The word FLASH was originally proposed by Toshiba because of the chip's ability to remove instantly. The flash memory is derived from EPROM, and the chip price is not high and the storage capacity is large. Flash is becoming an alternative to EPROM because they are easily upgraded. Flash memory is used for PCMCIA cards, PCMCIA flash drives, other forms of hard drives, embedded controllers and SMARTMEDIA. If flash or other related derivative technology can clear a byte in a certain amount of time, it will result in permanent (non-volatile) RAM.
DRAM
DRAM (DynamicRandom-AccessMemory), the most common system memory for dynamic random access memory. DRAM can only keep data for a short time. In order to maintain data, DRAM must be refreshed at intervals. If the storage unit is not refreshed, the data will be lost.
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