Has the camera in the dormitory been recording?

I suggest girlfriends who have such habits, please try to relax, and avoid conflicts in disputes is personal habit freedom. Personally, I suggest you spend a little money to buy a comfortable and high-grade pajamas for your girlfriend, which can be pure silk or pure cotton. The key is to make sure it's cool and let your girlfriend love to wear it.

..... will definitely be recorded. Now the most basic monitoring system should be equipped with a hard disk video recorder.

Unless-power failure (when the system has no backup power supply)

As for the recording time, it mainly depends on the model setting of the hard disk video recorder corresponding to the monitoring equipment and the size of the built-in hard disk.

According to the recording principle of hard disk video recorder

We can get the formula for calculating the recording time:

Recording time (hours) = total hard disk capacity (M)/ (hard disk space occupied per hour (M/ hour) x number of channels)

Hard disk video recorder adopts MPEG-4/H.264 compression technology, and its dynamic range is quite large. Therefore, in order to calculate the hard disk capacity, it is necessary to estimate the file size generated per hour per channel according to the code stream statistics.

For example:

Single channel video recording takes up 200M/ hour of hard disk space. When using 4-channel hard disk video recorder, it is required to record continuously 24 hours a day for one month (30 days). The required hard disk space is as follows: 4 channels × 30 days × 24 hours ×200m/ hour =576G, so it is generally necessary to install 5 120G hard disks or 4 160G.

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Common monitoring knowledge problems

Q: What is a CMOS camera? What's the difference with CCD camera?

A: CMOS sensor is a kind of sensor whose sensitivity is usually 10 times lower than that of CCD sensor. Because human eyes can see the target under the illumination below 1Lux (full moon night), CCD sensors can usually see the sensitivity of 0. 1~3Lux and 3 to 10 times that of CMOS sensors slightly better than human eyes.

Q: What is the physical meaning of light leakage suppression ratio?

Answer: The light leakage is caused by the design defect of CCD sensor. Each camera has a CCD sensor. Due to the defect of CCD sensor, the strong light entering CCD sensor will penetrate the resistive layer and produce too many images. These unnecessary images are called dragging light, and the ability of CCD camera to resist strong light is called light leakage suppression ratio.

Q: What do F2.0 and f3.4 mm mean? How do I choose the lens by these numbers?

A: F means the aperture of the lens, F stops at 2: 1, and f3.4 mm means the focal length of the lens is 3.4 mm. The lenses of F2.0 and f3.4~4 are very economical, so they are widely used in single-board cameras. The aperture of lens F2.0 can collect half the light of human eyes. The lens f3.4 mm has a 60-degree viewing angle on the 1/4-inch CCD and a 90-degree viewing angle on the 1/3-inch CCD, which is very close to the human eye. The two eyes of the human eye can accommodate a larger perspective, just like God's ingenious design. Depending on the person, there is generally an angle of 150 to 180, but please remember that the f-aperture and f-focal length are only basic parameters of a lens, and do not represent the quality. A high-quality lens with the same aperture and focal length can be 100 times more expensive than an inferior lens with the same parameters. Please refer to the next question and answer for details.

Q: What is the minimum illumination? What is sensitivity? What does 0.000 1Lux stand for?

A: Minimum illumination is a way to measure camera sensitivity. In other words, the camera can see available images in dark conditions. However, because there is no international standard for management, every large CCD manufacturer has its own method to measure CCD sensitivity. But a camera marked with (1Lux, F 10) can be exactly the same as a camera marked with (0.0 1Lux, F 10)! ! ! Is that weird? Why?

Q: What is colorless scrolling?

Answer: When the digital signal processor camera is used under fluorescent light, it can only produce images with severe color scrolling. The image will change from white to blue, from pink to white, and so on. This is because the AC power supply runs at a frequency of 50/60 Hz. White-hot bulbs can provide stable light, while the light of fluorescent lamps fluctuates due to the change of the intensity and color of alternating current at a speed of 8.3 ms. The white balance calculated by traditional cameras needs100 ~150 ms (0.1~ 0.15), which is 8.5ms slower than alternating current and will never catch up. For the current image, only 8 cycles can clearly produce color scrolling.

Q: What is backlight compensation?

Backlight compensation can provide the ideal exposure of the target in the face of very strong background light, no matter whether the main target moves to the middle, up and down, left and right or anywhere on the screen.

An ordinary camera without super dynamic characteristics only has a shutter speed of 1/60 seconds and an aperture of F2.0 However, a very bright background or a point light source behind a main target is inevitable. The camera will get the average of all the recent lights and decide the exposure level, which is not a good method, because when the shutter speed increases, the aperture will close and the main target will become too dark to see. In order to overcome this problem, a method called backlight compensation is widely used in most cameras through weighted region theory. Firstly, the image is divided into 7 blocks or 6 regions (two regions are repeated), and each region can be weighted independently to calculate the exposure. For example, the middle part can be increased to 9 times that of other blocks, so that an object in the middle of the picture can be seen very clearly, because the exposure is mainly calculated with reference to the illumination in the middle area. However, there is a very big defect. If the main target moves up, down, left and right on the screen, the target will become very black because it is not distinguished and is not weighted now.

Q: What is the starlight mode?

Starlight mode allows CCD cameras to see clear color images in very weak light conditions, such as 0.0002Lux illumination level.

All CCD cameras are designed to work at the shutter speed of 1/50, 1/60 ~ 1/2000 seconds, so the minimum illumination level or sensitivity is limited to 3 to 6Lux when F 1.2 and 5600k are used. The special digital signal processor for starlight CCD camera can make the shutter speed of CCD as low as 1~ 10 second. Due to the physical principle of long-term shutter opening, CCD can collect more photons, so its sensitivity is 100 to 600 times higher than that of traditional cameras.

Q: What are vertical synchronization, color video composite signal synchronization, external synchronization, DC line locking and complete synchronization?

A: This is a different synchronization method between cameras.

Integrated locking is the best way to completely synchronize two cameras in precision applications (such as radio studios). It will synchronize: horizontal, vertical, even/odd areas, color trigger frequency and phase.

Vertical synchronization is the easiest way to synchronize two cameras. By driving the frequency vertically, you can display video on the same monitor using the old-fashioned switching cycle or quadrant. The vertical driving signal usually consists of pulses with a repetition frequency of 20/ 16.7 milliseconds (50/60 Hz) and a pulse width of 1~3 milliseconds.

The color video composite signal represents video and color trigger signal, which means that the camera can be synchronized with the external composite color video signal. However, although it is called color video composite signal synchronization, it actually only performs horizontal synchronization and vertical synchronization, and there is no color trigger synchronization.

External synchronization is very similar to color video composite signal synchronization. One camera can synchronize with the video signal of another camera, and the external synchronization camera can extract the horizontal and vertical synchronization signals by using the input color video composite signal for synchronization.

DC line locking is an ancient technology, which uses DC 50/60 Hz power line current to synchronize the camera. Because DC 24 volt power supply is widely used in fire alarm systems of most buildings, it is very easy to obtain. Because the old switcher and segmentation system have no digital storage function, it is necessary to synchronize the cameras in order to maintain a stable image. DC line locking means that the camera is synchronized with AC 50/60 Hz. The time correlation between color channels and unconstrained horizontal/vertical signals will lead to poor color conversion (color phase design), so all users who use AC line locking will inevitably lose good color conversion. Fortunately, the existing splitters, 16-channel complex processors and hard disk video recorders all have internal memories to overcome this problem, and synchronization signals are no longer needed, so AC line locking may be eliminated within a few years.

What is the minimum height of CCD camera? Is it the limit of 1 1.5x50mm or 22X23?

Answer: The size of CCD camera mainly depends on the size of four main components, CCD sensor, digital signal processor, CDS and vertical drive. Because these chips must be made of different semiconductor technologies, it is impossible to combine them into a single IC. As the main part, CCD sensors have been greatly reduced, from 2/3 inches to 1/2 inches to 1/3 inches to 1/4 inches and 1/6 inches and 1/7 inches. Therefore, 1/6 inch CCD is much worse than 1/4 inch CCD, so 1/4 inch CCD has been the mainstream for many years. A 1/4 inch CCD has the size of 10X 10 mm as the main component. If the digital signal processor adopts QFPGA package of 15X 15 mm, it will be larger than CCD, further increasing the size of the camera single board. Nowadays, most companies can only reduce the size of CCD camera trigger to 44X44.

Q: What is ultra-wide dynamic?

Ultra-wide motion is a function that allows the camera to see images with very strong contrast.

Compared with the traditional 3: 1 dynamic range camera, the wide dynamic camera has exceeded several times. Natural light is arranged in the starry night 120000 lux to 0.00035Lux. When the camera looks out of the window from indoors, the indoor illumination is 100Lux, the outdoor illumination may be 10000 lux, and the contrast is10000/100 =100/. This contrast is easy for human eyes to see, because human eyes can handle the contrast of 1000: 1. However, the traditional closed-circuit surveillance camera will have great problems in processing. Traditional cameras only have a contrast ratio of 3: 1, so we can only choose to use the electronic shutter of 1/60 seconds to get the correct exposure of indoor objects, but the outdoor images will be erased. Or in another way, the camera selects 1/6000 seconds to get the perfect exposure of the outdoor image, but the indoor image will be cleared (all black). This is a defect that has existed since the invention of the camera.

Q: What is an ultra-high resolution CCD camera?

A: At present, almost all Sony CCD cameras on the market adopt ultra-high resolution technology. Compared with the traditional old CCD, the ultra-high resolution is 2 times more sensitive and the light leakage suppression ratio is 6dB higher.

Panasonic thinks that their latest 37 series is as good as Sony's ultra-high resolution, while the 39 series has the same effect as Sony EX-View in the visible range.

Compared with ultra-high resolution, Sony Ex-view CCD has four times the sensitivity in the near infrared region (800~900 nm), but this advantage can only be realized in night vision. If not used correctly, this advantage is almost useless, because infrared rays will lead to color distortion, and because of the deep focusing physical characteristics of infrared rays, the image will be blurred, especially when using some lenses.

Q: What is an ultra-high sensitivity camera? What are its advantages and disadvantages?

A: "EX-View" is a sensitivity enhancement technology developed by Sony to improve its CCD sensitivity. One is the factor of two visible light, and the other is four times the wavelength of near infrared wave.

EX-View is Sony's proprietary technology, and the P/N interface of each CCD basic photodiode has been specially assembled to obtain better photoelectric conversion efficiency. In addition, each photodiode (depicting a pixel on an image) is covered by a microlens, which can better record and focus light on an effective semiconductor interface. Compared with CCD provided by Sony, its visual range is increased by 2 times of visible light and 4 times of near infrared light (800~900 nm). The Lux efficiency of EX-View is twice that of high-quality "Super HAD" visible light and near-infrared light wave field.

The disadvantage of EX-View technology is that Sony can only provide limited sensors because of the difficulty of CCD chip manufacturing process and chip sensitivity.

According to Sony, compared with Super HAD sensor, the photodiode of EX-View chip has some potential defects. These defective CCD elements may fail, which will lead to "dead pixels" and leave some white or black spots in the image that cannot be removed. As we all know, the dead spots of CCD chips will increase continuously during storage or use.

For example, an EX-View CCD in Sony factory has only three dead spots, but it may increase to five during transportation, and to seven in the warehouse of camera manufacturer, and will continue to grow, for example, it will increase to 12 when installed on CCD cameras. When the cameras reach the users, the number may increase to 15 to 30. This process will continue until the defective photodiode stabilizes. Sony believes that the reason for the increase in the number of dead spots is that cosmic rays have destroyed some defective interfaces of CCD matrix.

Due to the photosensitive characteristics of the manufacturing process, the output of EX-View CCD chips is relatively low, and the units that can be used are limited. The high cost combination of manufacturing technology makes EX-View CCD chip more suitable for special fields (such as scientific research and industry). It is important to use high brightness and high sensitivity chips here, but it is not cost-effective to use them on ordinary surveillance cameras.

What is a starlight camera?

In starlight CCD camera, the photon on the CCD sensor is 2 to 128 times (1~2 seconds) longer than the maximum exposure time of ordinary CCD camera (1/60 or 1/50 seconds). Therefore, the minimum illumination of the usable image produced by the camera is reduced by 2 times, reaching 128 times. Using starlight camera with frame accumulation technology, users can see color images under starlight illumination (0.0035Lux) and black-and-white images under cloudy starlight illumination (0.0002Lux). The background light scattered in the city (such as light pollution) is enough to produce good color exposure.

What is peak sensing mode?

A: The peak sensing mode uses the bright spots of the image instead of the average value of the whole image to determine the exposure index. Users who use the rule system can meet the most demanding requirements, such as grabbing an image with white dots in the dark, but they can also see the details and colors of this small bright white dot.

Q: What is a CMOS camera? What's the difference with CCD camera?

A: CMOS sensor is a kind of sensor whose sensitivity is usually 10 times lower than that of CCD sensor.

Because human eyes can see the target under the illumination below 1Lux (full moon night), CCD sensors can usually see the sensitivity of 0. 1~3Lux and 3 to 10 times that of CMOS sensors slightly better than human eyes.