PROFESSIONAL class DVR.
DVR class «PROFESSIONAL»
WHAT'S INSIDE?
The cost of professional-class video recorders starts from 15 thousand rubles for a 4-channel model; 8- and 16-channel Prof*DVRs cost from 20-25 thousand rubles. What can we get for the considerable amount spent, and is the choice in favor of a professional series instead of a mid-class DVR justified? Let's try to answer these questions.
Compression format and recording quality
The 2010 trend – a complete transition to H.264 – concerns primarily professional-class recorders. Almost all models presented by suppliers in the spring-summer of 2010 have this compression format. High frame compression ratio with minimal loss in quality, resulting in an increase in archive depth and increased network speed. Resolution in PAL is 4CIF – 704×576 – this resolution is supported by all professional DVRs, as well as 2CIF (704×288) and CIF (352×288).
The recording speed is from 25 fps per channel in CIF format (352×288) to 6 fps per channel in 4CIF with a uniform system load. More subtle adjustments and settings for recording by channels and the corresponding redistribution of hardware capacities are possible. It is possible to increase the recording speed of some channels by reducing the speed of others. When redistributing the recording speed in the settings, it is important to remember that most DVRs use 4*channel video signal processors. Structurally, it looks like this (Fig. 1).
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Fig. 1. Camera switching diagram at the input |
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Each chip processes 100 fps on 4 channels at CIF resolution, and it is possible to set up a higher recording speed at maximum resolution only in one channel out of four (the other three will process the signal more slowly or with a lower resolution). An example of setting up at a resolution of 4CIF (704×576) on all channels is 1 channel 16 fps + 3 channels at 2 fps. 8* and 16*channel DVRs use 2 and 4 such chips, respectively, which allows setting up 2 and 4 «fast channels» respectively. It should be noted that there are models on the market in which the chip processes all 4 channels in 4CIF at 25 fps, but this is rare — or High*end class.
On average, at a speed of 400 fps per system and a CIF resolution (352×288) on a 16*channel video recorder with a 1000 GB hard drive, the archive depth will be about 7 days in continuous recording mode.
If you compare the above characteristics with the mid-range DVRs described in the previous article, you might think that they are identical for the professional class. But this is far from true. The hardware and software used with many settings in the professional DVR series allow you to get a very high-quality recording with a real resolution of more than 500 lines (in some cases, you can say: «what you saw when viewing, that's what you got in the recording»). In addition, they allow you to work with the DVR on the network at a higher level, including combining them into a large system, and also provide the user with many functions that are not available in mid-range DVRs.
For a more complete understanding of the DVR structure (and the use of professional-level equipment requires minimal knowledge of the issue), we present a simplified diagram of the DVR (Fig. 2).
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Fig. 2. DVR structural diagram |
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As some comments to the figure:
1. SDRAM memory is used both for the LINUX operating system and for storing video frames for «pre-recording».
2. The processor has a built-in SATA controller for connecting hard drives.
3. The video controller can be either with a built-in converter of a composite video signal to VGA, or with an external one.
Recording modes
The main recording modes for Prof-DVR are:
1. Continuous recording – recording occurs constantly (around the clock).
2. Scheduled recording – recording is activated at a set time.
3. By motion detection in the video frame.
4. By sound (the appearance of noise on the object).
5. By signal from external sensors of any type.
6. Combined recording. Example: continuous recording 2 fps, when movement appears in the frame, recording 25 fps, when movement disappears, switching to continuous recording 2 fps.
The motion detection algorithm in the frame is well implemented and allows to avoid false alarms. This is achieved by using more powerful video signal processing processors. The motion detector areas and sensitivity are configured. The «pre-recording» function is implemented — storing the last 5-10 seconds of video in memory will allow you not to miss an important event if the motion detector did not trigger immediately. When using this function, the previous few seconds of video will be added to the recording from the moment the motion detector was triggered.
We have already considered «scheduled recording», by sound, from external sensors in previous articles, so we will not dwell on them. The above functions are identical to the capabilities of a middle-class DVR. For the DVR class we are considering, the following function is worth noting:
DVR response to an event
Prof-DVR has a wide range of settings for the device's reaction to an event (by «event» we mean the start of recording by a motion detector, by sensors, by sound, etc.). Let's list the main actions that the DVR performs when motion appears in the frame (except for the start of recording):
1. Send a message about the event to the specified e-mail address. Some models send not only a text message, but also a still frame.
2. Turn on the buzzer built into the DVR to attract the attention of security.
Perform an action on the output relay by closing or opening the contacts. In 16-channel DVRs there are up to 4 output relays, each of which can be programmed individually and each of which can work with both one and several channels.
4. Display the image of the channel in which the event occurs on the alarm monitor (SPOT output).
5. Launching a pre-programmed program in a rotating dome camera connected via the RS-485 protocol. In this case, programs with viewing points and the order in which the camera's rotating device will pass them are pre-programmed in the SPEED-DOM camera, and the DVR launches a particular program. There can be up to eight or more programs on each camera.
This function allows you to fully automate the operation of rotating speed domes in the object's video surveillance system.
Additionally, it should be noted that each channel can be linked to one or more executive outputs, as well as the output can be used in conjunction with several video channels.
Additional functions
Compared to the middle class, the professional has the same functional capabilities. Additionally, the following can be noted:
? Direct printing of still frames to the printer, without using a computer (the same principle is used as when connecting a camera to the printer).
? Using «watermarks» when recording.
? Network capabilities not only exceed the middle class, but also make working with the recorder over the network more advanced:
1. Built-in web server allows you to connect to the recorder without installing special software via Internet Explorer + work with DVR via PDA and 3G devices.
2. Built-in mail client.
3. Work of several DVR in a single system + adjustment of network load.
4. Synchronization with world time via the Internet, automatic transition to summer/winter time.
5. Work with DDNS (DynDNS) services, which allow remote access to the recorder without the provider assigning a static IP address.
6. Ability to work with NAS drives not only in local networks, but also via the Internet.
7. Ability to independently establish a connection with the Internet provider (modem management).
8. Ability to organize two-way duplex audio communication between the recorder and a computer on the network.
Viewing and archiving
Since professional-class video recorders are equipped with high-quality network support, it is recommended to organize viewing via the network. For this, you can use small NetTop-class computers with pre-installed software from the recorder. Among the advantages are the ability to connect selective cameras from different recorders, the ability to organize a viewing and control point in any place where there is access to the network. The quality of viewing via the network is comparable to the quality of viewing through a connected monitor.
For direct connection to the DVR, there is a BNC connector, at the output of which we have a composite video signal with a resolution of 720×576. To connect the DVR to the LCD monitor, a VGA connector is used (in some DVI or HDMI) with a resolution from 1024×768 to 1920×1080. In professional video recorders, there is an additional SPOT video output, which is programmable at the user's discretion.
Archiving can be done via USB to external media (flash, HDD), to built-in DVD*RW drives and over the network using specialized software. Some models use external drive connections via esata or IEE1394 connectors. Archiving to NAS drives is supported. Viewing and converting video files on a computer is done using special software, usually included with the DVR or available on the manufacturer's website. The resulting file is usually in .avi format, suitable for viewing with a standard player on a computer.
WHERE AND HOW TO USE A PROFESSIONAL CLASS DVR
As in previous articles, we would like to point out that all recommendations for use are based on personal experience and are subjective.
The first area of application that can be indicated is use in the office of a large enterprise.
The need to identify visitors, control the work of personnel, control the work of cash desks and meeting rooms determine the need to use a high-quality registrar in
in conjunction with good high-resolution cameras. The second important reason can be considered high-quality work on the network and the ability to combine several DVRs into a system with remote access. Remote access will allow you to organize surveillance of remote objects within a single security system.
Large supermarkets. Cash desk control, the ability to work with CHEK-TV systems, the need to identify visitors and their actions with goods, etc. All these needs imply the use of a high-quality video recorder in conjunction with high-resolution cameras.
Banks, financial institutions. The quality of the recording (using appropriate cameras) allows identifying people and their actions, as well as registering the numbers of
cars both in the parking lot and passing by the building. This allows using professional-class recorders when monitoring ATMs, bank premises, and the adjacent territory not only for the general plan (as in the middle class), but also for identifying objects and actions.
Airports, train stations, stadiums, crowded places. Large flow of people, rapidly changing environment, integration with face recognition systems, the ability to control
rotating cameras, combining several DVRs into a system, quality of archive recordings are the main criteria for choosing professional equipment.
Safe City systems, traffic flow control. Many Prof DVR models can be integrated into complex security systems, where data exchange is carried out over the network and there are additional features, such as recognition of vehicle numbers, railway cars, face recognition.
Remote production facilities requiring high-quality recording, with communication lines and the ability to integrate into a single system.
Warehouses and production facilities with increased security requirements — again, recording quality and remote access for operational and non-operational
control. An alternative to the middle class DVR. If the client needs higher-quality recording and advanced network functions.
EQUIPMENT SET
As with the middle class DVR, in the professional class it is possible to use any cameras in accordance with the task. It is recommended to use color cameras with
WDR and a resolution of 560 TVL. When using a day/night camera with IR illumination and a resolution of 500/600 TVL outdoors, and simple color cameras with a resolution of 540 TVL indoors. Again, the main thing is to set the task correctly and select cameras in accordance with it, and a professional-class recorder will provide excellent quality and recording speed.
The system configuration is no different from a budget or medium solution, you can additionally consider:
? NAS*drive for archiving from one or more DVRs over the network. Creating a separate computer network for working with video recorders linked to the general building network.
? Using high-speed PTZ cameras (sometimes it is cheaper to install one simple and one PTZ camera instead of 4*5 regular ones, but the quality of the solution will be better).
? Executive devices (for example, an alert system).
SUMMARY
Let's draw final conclusions:
1. The use of professional recorders is justified in cases where:
? high recording quality is required;
? identification of people and their actions is required;
? remote access to the recorder over the network with advanced capabilities is needed;
? it is necessary to combine several DVRs into a system;
? registration of license plates of moving vehicles is required;
? control of external cameras using control automation is required;
? control of external devices in response to an event is required.
2. Recommended for use in the following areas:
? financial sector;
? large enterprises with increased security requirements;
? in trade (supermarkets);
? crowded places (airports, train stations);
? «Safe City» systems;
? in the widest range of tasks.
We remind you that in order to correctly select equipment for solving a specific problem and the optimal «price/result» ratio, it is better to contact specialists. Ideally, before drawing up the specification, an inspection of the site is necessary to identify all the nuances.
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S. Pigorev, director of Poliset+SB, A. Padom, director of Aladox
Magazine «Security Algorithm», No. 4, 2010