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Basic concepts and terminology of wireless video surveillance systems

Basic concepts and terminology of wireless video surveillance systems

1. The difference between a network camera and an analog camera

Analog camera, or camera, outputs CVBS analog video signals, PAL or NTSC. Analog cameras often use CCD devices, and CMOS devices are also currently used. There are various forms such as a gun machine, a hemisphere, and a ball machine. The ball machine has a built-in pan/tilt head that can be rotated up and down and left and right. The output interfaces are commonly found as BNC, Lotus, etc. Common analog cameras are shown below:

Basic concepts and terminology of wireless network video surveillance systems

The analog camera output signal can be directly connected to the TV for viewing, but cannot be transmitted to the remote end for viewing, because the original uncompressed video stream is too large to be transmitted and can only be viewed locally. To view it remotely, you must access a video encoder, such as DVR/DVS/HVR, etc., after compressing the video and reducing the stream to take the network to the remote end.

A network camera, or digital camera, is a lot different in appearance from an analog camera. It looks a lot like it, but the internal quality changes. The network camera has a built-in DSP board to compress the original video. The interface of the video output is Ethernet. The transmitted digital video stream is compressed, such as H.264 or early MPEG4/MJPEG.

2. Audio and video coding format

Video compression formats, in order of development, from early to recent:

MJPEG: In fact, it is a JPEG picture with low compression ratio and large output code rate. It has been eliminated.

MPEG4: The format adopted by VCD in the early years, the compression ratio is general, the code rate is still somewhat large, and it is rarely used at present;

H.264: Currently the most popular network video compression format, good image quality, high compression ratio, low output bit rate, most suitable for network transmission.

Audio compression format:

PCM/ADPCM: Basically the original audio;

G.72X: preliminary compression;

AMR:

Mp3: Using MPEG Audio Layer 3 technology, the music is compressed to a smaller file with a compression ratio of 1:10 or even 1:12, and for most users, the playback quality is the same as the original uncompressed audio. No significant decline;

AAC: Advanced audio coding.

3. Video Server / DVR / DVS / IPC / NVR / HVR terminology

1) The video server, ie DVS, performs the functions of video compression coding and network transmission;

2) DVR: In fact, the current functional aspects are no different from DVS;

3) IPC: IPcamera, that is, network camera, the difference with DVS/DVR is usually that DVR/DVS is mostly multi-channel video input, compression coding, hard disk/SD card video storage; and IPC refers to single-channel video encoder. Appear similar to an analog camera;

4) NVR: Network DVR, which can record the compressed digital video stream transmitted from the network to the built-in hard disk. It is mainly used with IPC to provide large-capacity video storage space for IPC and local decoding. display;

5) HVR: Hy brid NVR can be understood as a hy brid of DVR+NVR, which can support analog video input compression coded video storage at the same time, and can also support digital video cable input video to save to hard disk;

Common Terms for 4.3G Wireless Video Surveillance Products

3G wireless video surveillance products, or 3G wireless video servers, 3G individual soldiers, 3G network cameras, 3G cameras, etc., are all concepts, that is, after using DSP to compress and encode the input audio and video, all the way to local video storage, all the way The 3G wireless network is transmitted to the remote monitoring center.

Mainly used in mobile video surveillance, vehicle monitoring, emergency, burst, temporary live audio and video transmission to the monitoring center in real time, in fact, not a full sense of monitoring, but a live real-time image transmission, live video concept.

A front-end device for video capture, coding, and network transmission, that is, a network camera, usually called a PU;

The PU collects video, compresses the code, and establishes a network waiting for the CU (client) to take the flow. The videos of these PUs are summarized in a network video centralized monitoring software, that is, the client CU performs aggregation, that is, one CU can consult multiple The video of the front-end PU can also refer to the video of one PU at the same time by multiple CUs;

And 3G wireless monitoring products, usually need a streaming media server in the middle, we can become SERVER, or CMS / VTDU.

Commonly used network streaming media transmission, control, and communication protocols are: RTP/RTSP/SIP.

5. About the resolution of the video

In the scope of SD, take PAL as an example:

CIF: 352x288; D1: 704x576;

In addition, there is a VGA resolution of 640x480

The current HD has three display resolution formats: 720P (1280×720, progressive), 1080i (1920×1080, interlaced), and 1080P (1920×1080, progressive), where p stands for English word progressive (progressive) ), while i is interlaced (interlaced).

6. Technical route for 3G image transmission and wireless video surveillance products

1) 2007~2009, our handheld soldier and wireless video server are all based on ADSP BLACKFIN BF561 platform single chip. This series of products is characterized by H.264 BP CIF code rate can provide good at around 30~80kbps. Real-time image effects, low bit rate is the biggest advantage; the disadvantage is that compression can only go to CIF dual stream, it is difficult to support D1; see:

Http://user.qzone.qq.com/47606446/infocenter#!app=4&via=QZ.HashRefresh

Http://www.analog.com/en/processors-dsp/blackfin/content/besovideo_eyes_blackfin_security_camera_new/fca.html

http://www.analog.com/en/content/local_tools_Bestvideo_index/fca.html

2) 2009~2011, using DAVINCI DM644X and DM36X, featuring DSP, can do intelligent analysis of video, we successfully productized face recognition, behavior recognition, perimeter defense, ATM intelligent guard products, etc. One feature, DAVINCI can support HD-SDI digital HD video input, see:

Http://user.qzone.qq.com/47606446/infocenter#!app=4&via=QZ.HashRefresh

The disadvantage is that compared with the rising star HiSili, in the application of typical security products such as DVR, the interface richness is slightly thin, and the multi-channel DVR/MDVR products are costly;

3) From 2011 to 2013, using the HiSilicon HI351X series to realize a lower cost multi-channel car hard disk + SD card recorder, see:

http://www.besovideo.com/chn/products/mdvr_VC_A.asp

However, the power consumption is too big.

7. About the 3G system description

The telecommunications network is: 2G CDMA1x (can also transmit CIF video, but not the Unicom CDMA annual data card of the year), 3G is EVDO/CDMA2000;

China Unicom's 3G network is: WCDMA

The mobile 3G is: TD-SCDMA, the bandwidth is very low, but soon 4G is surging;

For our 3G graphics manufacturers, 3G/4G is a replacement for a USB module;

8. Description of 3G dual card and multi card

The dual-card or multi-card transmission mentioned in the 3G picture refers to the fact that multiple 3G modules are built in the device. Multiple 3G modules are dial-up at the same time, and the uplink transmission bandwidth is effectively bundled by our protocol software to transmit the video stream. .

The reason for adopting multi-card transmission is because the uplink transmission bandwidth of a single 3G module is limited, typically:

Uplink bandwidth of telecom 3G/EVDO is usually: 300~500kbps

The upstream bandwidth of China Unicom's 3G/WCDMA is usually 400~600kbps.

Moreover, this bandwidth fluctuation is more serious. It is better to transmit the bit rate of H.264 MP@CIF 300kbps on a single card. However, when the D1 code rate of 800kbps~1.3Mbps is transmitted, the single card is very difficult, in order to To transmit a D1 or higher definition video stream, we need bandwidth bundling of multiple 3G modules for transmission.

In the dual card, two 3G modules are used at the same time, not one master and one standby; of course, the dual card device can disable one of the 3G modules and use it as a single card device;

Multiple 3G modules can be used in any combination, such as a telecommunications-unicom, or dual telecommunications, or dual connectivity. Of course, a telecommunications and Unicom is an ideal combination to achieve complementarity of heterogeneous networks.

9. The difference between 3G wireless transmission and microwave wireless transmission

3G wireless image transmission
Distance limitation No, as long as there is a 3G network signal, the live image can be transmitted to any place anytime, anywhere. There must be an OB van or a relay base station (COFDM).
Cost The construction cost is low, the initial investment is small, but the cost will be generated in the later transmission process. The initial project investment is large, but the later cost is small.
Bandwidth guarantee and transmission effect Fluctuation in 3G network will cause fluctuations in image fluency. As long as there is no occlusion, bandwidth is guaranteed, and it is relatively stable and reliable.

10. What does the P and N systems of the analog camera mean?

PAL, NTSC, and SEcam, which are the current three color analog TV systems in the world. The so-called standard is a technical standard for processing video and audio signals jointly implemented by TV stations and television sets. Only the same technical standards can realize the normal acceptance of the signals of the TV set. Just like the power socket and plug at home, the specifications can be plugged together. The plug of China can't be plugged into the British power socket, only the standard can be docked smoothly.

The image display of the color TV is made up of red, green and blue three primary color signals. The different brightness of the three color signals constitutes a colorful color picture. How to deal with the three primary color signals, and to achieve broadcasting and receiving, requires certain technical standards, which form the format of color television. At present, there are three color TV systems with analog technology in the world, namely NTSC (also known as N, or American), PAL (also known as Par or West German, British), and SEcam (also Called Sekon or French). The distinction between the system is mainly due to the difference in frame rate (field frequency), the difference in decomposition rate, the difference in signal bandwidth and carrier frequency, and the difference in the conversion relationship of color space.

PAL (Phase Alternating Line) is a television system established in 1965. It is mainly used in China, Hong Kong, the Middle East and Europe. The color bandwidth of this system is 4.43Mhz with a sound bandwidth of 6.5Mhz and 25 frames per second.

The NTSC (National Television System Committee) standard is a color television broadcasting standard established by the National Television Development Committee in 1952. The United States, Canada, and Japan, Taiwan, South Korea, the Philippines and other countries use this system. This system has a color bandwidth of 3.58Mhz and a sound bandwidth of 6.0Mhz, 30 frames per second.

Why NTSC is 30 frames per second, and PAL is 25 frames per second. This is because the power supply of the country using NTSC is 110V\60HZ, so the field frequency signal in the TV directly samples the frequency of the AC power source 60HZ because The two fields form a frame, so 60 divided by 2 equals 30 is exactly the number of frames of the TV, and China's mains is 220V\50HZ, so the reason is the same as 25 frames per second.

11. The horizontal resolution line of the analog camera

The horizontal resolution line of the analog camera is a key indicator for reflecting the resolution of a camera. Commonly, for example, 420TVL, 480TVL, 540TVL (color mode) is now close to the limit values of 650TVL (color mode) and 700TVL (black and white mode).

The so-called high-line analog camera usually means that the true resolution reaches 480TVL or above. The industry generally uses the CCD specification model as the watershed. Taking the SONY CCD as an example, the real high-line analog camera should be equipped with at least 1/3'SONY ICX639BK. The CCD or 1/4'SONY ICX649AK CCD, which is lower than this specification, is not a true high line. In terms of technical solutions, the high-line analog camera uses a 960H CCD, and its effective pixels can reach 976*582. The ISP uses the SONY EFFIO series chip. In terms of definition, the output video of the high-resolution camera also uses the CVBS signal, but The horizontal resolution is up to 700 lines, which is much higher than that of ordinary analog cameras.