PTZ camera control over the network. PTZ camera - what is it? How to control access to control your camera when making a call from TrueConf for Windows

I.V. Oleinik
DSSL CEO

This overview focuses on how to control SpeedDome integrated PTZ cameras.

The consumption of PTZ cameras has grown significantly in the market over the past 10 years. A significant reduction in the price of these devices is affecting, as well as an increase in their technical capabilities: speed, optical zoom, functionality. Now the normal rotation speed during the setting of the "preset" reaches (often exceeds) 400 degrees / s, the optical zoom has long stepped over 30x, and some cameras have even gained the ability to track objects in their field of view on their own. Modern prices for domes range from $500 to $600 for Chinese brands to several thousand euros for well-known Japanese, American or European brands. Unlike individual pan and tilt mechanisms, where control is carried out by its own pair for each degree of freedom (mainly 24 or 220 V alternating voltage), a telemetry receiver is integrated into the SpeedDome, which allows you to control the camera with just two wires (in the case of RS-485; some models require 4 wires for duplex control) or video cable. Well, SpeedDome IP video cameras do not require additional control wires at all, although they usually have the ability to work "the old fashioned way".

Controllers and keyboards

The easiest and "ancient" way to control a Speed ​​Dome camera is with a keyboard, as well as a separate stand-alone device with its own power source. The minimum cost keyboard will control pan and zoom using only buttons and RS-485 protocol. Buttons are quite enough when you only need to set up cameras and then manage, for example, presets. But if the operator needs to constantly control the cameras, the remote control will greatly slow down his work. For such cases, a remote control with a joystick will be much more convenient - it allows you to control the camera in two coordinates at once, focal length lens, as well as the speed of rotation with one movement of the hand. The higher the cost of the keyboard, the more additional features (for example, control of video recorders, displaying signals from video cameras and recorders on the built-in TFT monitor) it has. Working with DVRs is limited only by the fact that they must be released by the same company as the keyboard; there are no such problems with controlling video cameras - usually remotes support several protocols, which means that you can control cameras from different manufacturers. With the advent of IP-cameras, the question of remote controllers for them arose with an edge. Of course, almost all PTZ IP cameras have the ability to control via RS-485, but it makes no sense to drag additional wires when there is already a high-bandwidth digital network. The only drawback of an Ethernet network based on copper UTP, which is the basis for 99% of IP video systems, compared to an analog network is the short segment length from the device to the switch (about a hundred meters if you do not use optics).

PTZ camera features

Here we can talk about two things. First, some camcorders have built-in advanced controls. An appropriately configured video camera constantly monitors with a maximum viewing angle. When the built-in motion detector detects motion, the camera zooms in on the area and "leads" the moving object as far as possible. At the moment of such tracking, the camera "does not see" the environment and cannot switch to another object without returning to its original position with a minimum zoom. Of course, not all cameras even have a built-in motion detector, let alone automatic tracking.

The second applies only to IP cameras. It has already been said above that the Speed ​​Dome IP camera can be controlled both using a conventional remote control and an IP remote control. However, IP PTZ cameras are, in a sense, self-sufficient devices and "have on board" a Web server. By logging in from any computer through a Web browser, you can get the image from the camera, configure its settings and control the pan and lens. It offers 2 methods - a simple one that imitates the buttons of the control panel and allows you to simultaneously control two coordinates, and an advanced one that differs for each manufacturer in details. Here you control the rotation and scaling with your computer mouse. By drawing a rectangle in any part of the camera window, you will force it to zoom in on this area or, by moving the cursor to the edge of the image, you will get an arrow hint; which you can move the camera in the desired direction (at the left edge - to the left, at the right - to the right, and so on).

Control by DVR non-PC

PTZ camera control has been an integral basic function of DVRs for a very long time. Only very cheap and very limited DVRs can afford not to have one. Cameras with non-PC DVRs are controlled in 99% of cases using the RS-485 interface. Some newer hybrid recorders that can work with both analog and IP cameras may support control over IP. According to the control method, all DVRs can be divided into 3 types: those that control using the keyboard of the DVR (from the front panel), control only the mouse (for recorders where there is no keyboard) and DVRs that support both options. The first option is acceptable only for those who very rarely use manual control of PTZ cameras (cameras are configured to bypass "presets" or "tours" in automatic mode). In most cases, using the front panel of a video recorder to control a PTZ camera is a pain in the ass, as there are only limited buttons to work with: no 3D joysticks. Mouse control can also vary greatly. The simple version is an imitation of the same limited set of buttons from the front panel, it is not much more convenient. Other NVRs may use roughly the same mechanism as described in the previous section, which is found mostly in IP cameras. Of course, you will have to configure everything using the same buttons or on-screen menu, but this is the only option for all DVRs. Total: the mouse is good, the keyboard is not very good. The good news is that there are more and more mouse-controlled registrars, but even the latter's internal software can vary greatly.

The control methods listed above have one common drawback. Any Speed ​​Dome camera has 2 control speeds. The speed of control in manual mode usually does not exceed even half the speed of turning the camera at the time of using the presets. At the same time, it is obvious that the higher the speed of such manual control, the less accurate, the accuracy of positioning the camera on the area or object of interest. It can be noted here that the camera is not used to 100% of its capabilities, and the efficiency of its use could be higher. New computer interfaces and developments are called upon to cope with this task.

Software (PC-based DVR)

Computer DVRs always outperform non-PCs. Firstly, new technologies, especially resource-intensive and complex ones, are easier to develop and debug on computers, and secondly, competition with DVRs based on embedded processors forces the same developers to constantly add new features and capabilities, make their software more flexible and powerful. . What new software developers offer us for video recording and control of PTZ cameras? If we discard the variations associated with the interactivity of control directly on the image, or the imitation of a 2D joystick, then 3 categories of new products (interfaces) can be distinguished separately. The first is adding the ability to automatically control those cameras that do not have it initially, that is, controlling the camera using a motion detector in software. Such detectors can be more powerful and advanced than those built into cameras. The second and third are connected with the use of at least one more video camera (review), the field of view of which coincides completely or partially with the rotary one at the minimum value of the focal length.

Manual control

In this mode, a combination of a survey and PTZ camera allows the operator to control the PTZ camera with one mouse click or, by selecting a rectangular area of ​​the image from the survey camera, to get it optically enlarged using the PTZ camera. At the same time, 2 drawbacks of the interfaces described above disappear at once, control is performed at the maximum speed1 available for the video camera (usually declared as the positioning speed according to presets), and the operator does not lose sight of the protected area - he sees the whole situation as a whole and its details with maximum optical zoom, so it can move the camera from one position to another as quickly as it could with traditional interfaces.

The fact that the Speed ​​Dome does not need to return to the viewing position in order to select new object, and this, as already noted, is the slowest part of positioning. When the camera is positioned without major zoom changes (almost not using the zoom), the speed increases significantly.

Automatic control

This implies the same bundle of overview and PTZ cameras. The motion detector analyzes the image from the overview camera and sends commands to the PTZ camera - now the control is fully automatic. Systems of this kind appeared many years ago, however, then they worked according to presets - each square of the overview camera image was assigned its own position, and as we remember, Speed ​​Dome can have up to 256 presets. However, now developers use the capabilities of not only modern detectors, but also video cameras. The detectors are smart enough to transmit not just the coordinates of the object, but also the vector of its movement, since while the camera is turning towards the object, it may already have shifted. And the cameras have the ability not only to work according to presets, but also to execute direct commands to install at certain coordinates; they also have sufficient speed. It should only be noted that not all Speed ​​Dome cameras, even from the average price range, will support these functions. You should not expect that the Chinese noname will be as fast and will have a fully implemented protocol, especially a borrowed one. If several objects appear in the field of view of the overview camera, the PTZ camera will switch between them, following each one for the set time. Today, some developers are supplying systems that allow simultaneous control of multiple Speed ​​Dome cameras, and virtually unlimited combinations of panoramic and PTZ cameras, where you can have a live view of what is happening 360 ° around, while providing high resolution and detail of moving objects. It would seem that with the increase in resolution, when there are already digital video cameras of 5.8 Mpx and more, the need for such a solution is not so high. But the optical zoom is still difficult to replace, and a combination of panoramic and PTZ cameras using, for example, 35x zoom gives the equivalent of a system resolution of more than 300 megapixels - digital cameras will not be able to achieve the same result soon. Again, the use of megapixel panoramic and PTZ cameras will always push this barrier forward. Of course, this system also has disadvantages. First, as mentioned, not all PTZ cameras are compatible, and not all of them are fast enough to track objects moving at high angular velocity. Secondly, the system increases in price (however, the fee is worth it - like any increase in functionality that increases the security of the facility or your enterprise). Thirdly, the system requires calibration - setting the coordinates of the overview and PTZ cameras (although there are positive shifts here - for some cameras you need to set only 9 coordinate anchor points, and the rest will be calculated by the system itself).

It can be noted in which direction we should expect the development of manual and automatic control technology:

• transition to megapixel panoramic and PTZ cameras and the desire for higher resolution;
• construction panoramic images, made up of pictures obtained from a variety of survey cameras, which also contain images of rotary cameras. Thus, a single interactive scene of an object or its section is created. However, it will be inferior without the ability to reproduce the archive in the same way (although this can be a serious load on the server);
• improving the performance of motion detectors. New tracing technologies, scene and object recognition, improved tracing quality at night.

Of course, one should not rely entirely on the capabilities of the detectors. It is not worth saving on video cameras, hoping that the detector will cope with both noise and low-resolution images. The general rule for any security system is that a system will only be as bad as its smallest component. A cheap lens attached to an expensive camera, a cable with a low-quality connector, or any other component can wipe out all your costs.

Glossary

Speed ​​Dome is a speed dome PTZ camera. High-speed in comparison with usual rotary mechanisms. Dome, since more than 90% of such cameras are designed as a cylinder with a domed optically transparent casing that protects the optics and mechanism from dust and moisture. Speed ​​Dome cameras are also called integrated, meaning that all the necessary components are assembled in one body: the video camera itself, optics, a two-axis mechanism and a telemetry receiver.

Preset - the ability of the Speed ​​Dome to be set to a pre-programmed position with the maximum available speed. Various modifications can store from 32 to 256 presets.

Tours (Tour, or Touring) - the ability of a PTZ video camera to execute a series of commands, such as a sequence of presets. The advanced option involves the camera remembering your actions and then cyclic execution. Protocol - a set of commands for controlling PTZ cameras using a telemetry receiver. Usually, large manufacturers use their own protocol, but they also necessarily integrate additional Pelco types, which have become the de facto standard due to the openness of the manufacturer's policy. Small manufacturers use only such open protocols and implement (depending on their laziness or camera capabilities) only a part of the commands. PTZ is an abbreviation for Pan, Tilt and Zoom, respectively horizontal and vertical rotation and lens control. A PTZ camera is a correspondingly integrated camera with a swivel mechanism and a zoom lens.

This review focuses on how to control the Speed ​​Dome integrated PTZ cameras.

The consumption of PTZ cameras has grown significantly in the market over the past 10 years. A significant reduction in the price of these devices is affecting, as well as an increase in their technical capabilities: speed, optical zoom, functionality. Now the normal rotation speed during the setting of the "preset" reaches (often exceeds) 400 degrees / s, the optical zoom has long stepped over 30x, and some cameras have even gained the ability to track objects in their field of view on their own.

Modern prices for domes range from $500 to $600 for Chinese brands to several thousand euros for well-known Japanese, American or European brands. Unlike individual pan and tilt mechanisms, where control is carried out by its own pair for each degree of freedom (mainly 24 or 220 V alternating voltage), a telemetry receiver is integrated into the SpeedDome, which allows you to control the camera with just two wires (in the case of RS-485; some models require 4 wires for duplex control) or video cable. Well, SpeedDome IP video cameras do not require additional control wires at all, although they usually have the ability to work "the old fashioned way".

Controllers and keyboards

The easiest and "ancient" way to control a Speed ​​Dome camera is with a keyboard, as well as a separate stand-alone device with its own power source. The minimum cost keyboard will control pan and zoom using only buttons and RS-485 protocol. Buttons are quite enough when you only need to set up cameras and then manage, for example, presets. But if the operator needs to constantly control the cameras, the remote control will greatly slow down his work. For such cases, a remote control with a joystick will be much more convenient - it allows you to control the camera in two coordinates at once, the focal length of the lens, as well as the rotation speed with one hand movement. The higher the cost of the keyboard, the more additional features (for example, control of video recorders, displaying signals from video cameras and recorders on the built-in TFT monitor) it has. Working with DVRs is limited only by the fact that they must be released by the same company as the keyboard; there are no such problems with controlling video cameras - usually remotes support several protocols, which means that you can control cameras from different manufacturers. With the advent of IP-cameras, the question of remote controllers for them arose with an edge. Of course, almost all PTZ IP cameras have the ability to control via RS-485, but it makes no sense to drag additional wires when there is already a high-bandwidth digital network. The only drawback of an Ethernet network based on copper UTP, which is the basis for 99% of IP video systems, compared to an analog network is the short segment length from the device to the switch (about a hundred meters if you do not use optics).

PTZ camera features

Here we can talk about two things. First, some camcorders have built-in advanced controls. An appropriately configured video camera constantly monitors with a maximum viewing angle. When the built-in motion detector detects motion, the camera zooms in on the area and "leads" the moving object as far as possible. At the moment of such tracking, the camera "does not see" the environment and cannot switch to another object without returning to its original position with a minimum zoom. Of course, not all cameras even have a built-in motion detector, let alone automatic tracking.

The second applies only to IP cameras. It has already been said above that the Speed ​​Dome IP camera can be controlled both using a conventional remote control and an IP remote control. However, IP PTZ cameras are, in a sense, self-sufficient devices and "have on board" a Web server. By logging in from any computer through a Web browser, you can get the image from the camera, configure its settings and control the pan and lens. It offers 2 methods - a simple one that imitates the buttons of the control panel and allows you to simultaneously control two coordinates, and an advanced one that differs for each manufacturer in details. Here you control the rotation and scaling with your computer mouse. By drawing a rectangle in any part of the camera window, you will force it to zoom in on this area or, by moving the cursor to the edge of the image, you will get an arrow hint; which you can move the camera in the desired direction (at the left edge - to the left, at the right - to the right, and so on).

Control by DVR non-PC

PTZ camera control has been an integral basic function of DVRs for a very long time. Only very cheap and very limited DVRs can afford not to have one. Cameras with non-PC DVRs are controlled in 99% of cases using the RS-485 interface. Some newer hybrid recorders that can work with both analog and IP cameras may support control over IP. According to the control method, all DVRs can be divided into 3 types: those that control using the keyboard of the DVR (from the front panel), control only the mouse (for recorders where there is no keyboard) and DVRs that support both options. The first option is acceptable only for those who very rarely use manual control of PTZ cameras (cameras are configured to bypass "presets" or "tours" in automatic mode). In most cases, using the front panel of a video recorder to control a PTZ camera is a pain in the ass, as there are only limited buttons to work with: no 3D joysticks. Mouse control can also vary greatly. The simple version is an imitation of the same limited set of buttons from the front panel, it is not much more convenient. Other NVRs may use roughly the same mechanism as described in the previous section, which is found mostly in IP cameras. Of course, you will have to configure everything using the same buttons or on-screen menu, but this is the only option for all DVRs. Total: the mouse is good, the keyboard is not very good. The good news is that there are more and more mouse-controlled registrars, but even the latter's internal software can vary greatly.

The control methods listed above have one common drawback. Any Speed ​​Dome camera has 2 control speeds. The speed of control in manual mode usually does not exceed even half the speed of turning the camera at the time of using the presets. At the same time, it is obvious that the higher the speed of such manual control, the less accurate, the accuracy of positioning the camera on the area or object of interest. It can be noted here that the camera is not used to 100% of its capabilities, and the efficiency of its use could be higher. New computer interfaces and developments are called upon to cope with this task.

Software (PC-based DVR)

Computer DVRs always outperform non-PCs. Firstly, new technologies, especially resource-intensive and complex ones, are easier to develop and debug on computers, and secondly, competition with DVRs based on embedded processors forces the same developers to constantly add new features and capabilities, make their software more flexible and powerful. . What new software developers offer us for video recording and control of PTZ cameras? If we discard the variations associated with the interactivity of control directly on the image, or the imitation of a 2D joystick, then 3 categories of new products (interfaces) can be distinguished separately. The first is adding the ability to automatically control those cameras that do not have it initially, that is, controlling the camera using a motion detector in the software. Such detectors can be more powerful and advanced than those built into cameras. The second and third are connected with the use of at least one more video camera (review), the field of view of which coincides completely or partially with the rotary one at the minimum value of the focal length.

Manual control

In this mode, a combination of a survey and PTZ camera allows the operator to control the PTZ camera with one mouse click or, by selecting a rectangular area of ​​the image from the survey camera, to get it optically enlarged using the PTZ camera. At the same time, 2 drawbacks of the interfaces described above disappear at once, control is performed at the maximum speed1 available for the video camera (usually declared as the positioning speed according to presets), and the operator does not lose sight of the protected area - he sees the whole situation as a whole and its details with maximum optical zoom, so it can move the camera from one position to another as quickly as it could with traditional interfaces.

The fact that the Speed ​​Dome camera does not need to return to the viewing position in order to select a new object also plays its role in the speed of control, and this, as already noted, is the slowest part of positioning. When the camera is positioned without major zoom changes (almost not using the zoom), the speed increases significantly.

Automatic control

This implies the same bundle of overview and PTZ cameras. The motion detector analyzes the image from the overview camera and sends commands to the PTZ camera - now the control is fully automatic. Systems of this kind appeared many years ago, however, then they worked according to presets - each square of the overview camera image was assigned its own position, and as we remember, Speed ​​Dome can have up to 256 presets. However, now developers use the capabilities of not only modern detectors, but also video cameras. The detectors are smart enough to transmit not just the coordinates of the object, but also the vector of its movement, since while the camera is turning towards the object, it may already have shifted. And the cameras have the ability not only to work according to presets, but also to execute direct commands to install at certain coordinates; they also have sufficient speed. It should only be noted that not all Speed ​​Dome cameras, even from the average price range, will support these functions. You should not expect that the Chinese noname will be as fast and will have a fully implemented protocol, especially a borrowed one. If several objects appear in the field of view of the overview camera, the PTZ camera will switch between them, following each one for the set time. Today, some developers are supplying systems that allow simultaneous control of multiple Speed ​​Dome cameras, and virtually unlimited combinations of panoramic and PTZ cameras, where you can have a live view of what is happening 360 ° around, while providing high resolution and detail of moving objects. It would seem that with the increase in resolution, when there are already digital video cameras of 5.8 Mpx and more, the need for such a solution is not so high. But the optical zoom is still difficult to replace, and a combination of panoramic and PTZ cameras using, for example, 35x zoom gives the equivalent of a system resolution of more than 300 megapixels - digital cameras will not be able to achieve the same result soon. Again, the use of megapixel panoramic and PTZ cameras will always push this barrier forward. Of course, this system also has disadvantages. First, as mentioned, not all PTZ cameras are compatible, and not all of them are fast enough to track objects moving at high angular velocity. Secondly, the system increases in price (however, the fee is worth it - like any increase in functionality that increases the security of the facility or your enterprise). Thirdly, the system requires calibration - setting the coordinates of the overview and PTZ cameras (although there are positive shifts here - for some cameras you need to set only 9 coordinate anchor points, and the rest will be calculated by the system itself).

It can be noted in which direction we should expect the development of manual and automatic control technology:

Switching to megapixel panoramic and PTZ cameras and striving for higher resolution;
construction of panoramic images, composed of images received from a plurality of survey cameras, which also include images of rotary ones. Thus, a single interactive scene of an object or its section is created. However, it will be inferior without the ability to reproduce the archive in the same way (although this can be a serious load on the server);
improving the performance of motion detectors. New tracing technologies, scene and object recognition, improved tracing quality at night.
Of course, one should not rely entirely on the capabilities of the detectors. It is not worth saving on video cameras, hoping that the detector will cope with both noise and low-resolution images. The general rule for any security system is that a system will only be as bad as its smallest component. A cheap lens attached to an expensive camera, a cable with a low-quality connector, or any other component can wipe out all your costs.

Glossary

Speed ​​Dome- speed dome PTZ camera. High-speed in comparison with usual rotary mechanisms. Dome, since more than 90% of such cameras are designed as a cylinder with a domed optically transparent casing that protects the optics and mechanism from dust and moisture. Speed ​​Dome cameras are also called integrated, meaning that all the necessary components are assembled in one body: the video camera itself, optics, a two-axis mechanism and a telemetry receiver.

preset- the ability of the Speed ​​Dome to be set to a pre-programmed position with the maximum available speed. Various modifications can store from 32 to 256 presets.

Tours(Tour, or Touring) - the ability of a PTZ video camera to execute a series of commands, such as a sequence of presets. The advanced option involves the camera remembering your actions and then cyclic execution. Protocol - a set of commands for controlling PTZ cameras using a telemetry receiver. Usually, large manufacturers use their own protocol, but they also necessarily integrate additional Pelco types, which have become the de facto standard due to the openness of the manufacturer's policy. Small manufacturers use only such open protocols and implement (depending on their laziness or camera capabilities) only a part of the commands. PTZ is an abbreviation for Pan, Tilt and Zoom, respectively horizontal and vertical rotation and lens control. A PTZ camera is a correspondingly integrated camera with a swivel mechanism and a zoom lens.

Came briefly into the hands of the PTZ (managed) camera CNB-M1360PL. This type of camera is controlled by Rs-485 interface, usually using the Pelco-D protocol. Of the control options, the protocol supports: panning, tilting vertically, zoom, focus, iris, OSD (on-screen menu), various settings and various other features. But not always all of the above may be present on the selected camera, the camera that fell into the hands of the available ones: zoom, focus and on / off.

In the article I will share my experience of communicating with this camera, a description of the Pelco D protocol, a program for checking such cameras, and an example of implementing a camera control code for Rs-485 using the Pelco D protocol.

Larger view of the camera.

This, one might say, is a modular, without a case video camera, it is one of the cheapest and most affordable, the average price is around 6000 rubles (at the time of writing the article on 11/04/2017). True, it is without a turntable in the kit, which is a little sad for the first acquaintance with such cameras. The camera is equipped with 12x optical zoom and up to 120x digital zoom, auto focus, day/night mode switching and other standard features for custom video cameras. From the control on this camera is available: zoom, focus and on / off.

It can be equipped with an OSD control board for the camera menu, on which there is also a BNC video output connector, connectors for connecting power and Rs-485 lines, and a UART-Rs485 interface converter. In this case, only the Tx line with a logic level of 5V goes to the camera.

In the photo of the control board, top view, 1 pin is signed on the connector.

The on-screen menu is controlled by 5 buttons via the ad-key interface, which I have already considered using the example of a simple modular video camera -. The button connection scheme is slightly different from the one drawn earlier, but the meaning is the same.

The buttons in this camera are responsible not only for navigating the on-screen menu, but also for controlling zoom and focus.

In the on-screen menu, in addition to the image settings, you can select one of the two control protocols Pelco D or DXP and set the camera number for its addressing on the Rs-485 line. On one line, you can put several cameras with the same numbers to control them simultaneously or with different numbers for separate control. Interface settings: speed 2400 and standard 8N1. Other cameras may have different speeds, but they are in the standard range of 2400 to 115200.

Pelco D

Brief description of the Pelco D protocol.
Packages of 7 bytes are sent to the cameras from the remote control:

Checksum - 1 byte is equal to the sum of 5 bytes: from 2 to 6.

The Pelco D protocol can send 15 standard commands to control cameras, it can be used to remotely configure cameras (but not all cameras support this or their manufacturers use non-standard / custom commands and carefully hide them) and control the OSD menu (also not all cameras support). Because the copy on hand supports only a limited set of standard commands, then I will not consider additional options for remote camera configuration.

Standard commands:

The Sense bit is shared with the Auto/Manual Scan and Camera on/off bits.

I note that after turning on commands for movement along the axes or focus and zoom, the camera will move until it reaches the end position. You can stop the movement with the "stop" command.

On the Internet you can find detailed description Pelco-D protocol in English.

When working with the camera, I connected it to a computer through a 2-dollar USB-Rs485 converter (in the first photo in the lower right corner), built on the basis of a USB-UART ch340 interface converter and a UART-Rs485 MAX485 converter. This, the cheapest converter, does not have galvanic isolation and only 2 outputs Rs485 A + and A-, there is no common wire! When connecting equipment via 485 lines, it is desirable to use galvanic isolation and also connect the converters with a common wire, because if the power circuits of the devices are not connected by them over long distances, the devices may not work correctly, malfunction or burn out. What happened to me, but with a wire length of ~ 60 cm. The converter was connected to the computer, and the camera was powered by a laboratory power supply, but the power supply did not have a ground wire (I forgot that it was the PSU used that had no ground on the mains plug, all other laboratory equipment and a computer at the workplace did), which turning it on and off caused the MAX485 chip to burn out in the Chinese converter. Be more careful and, better, do not save on converters and wires.

Utility for testing cameras with Pelco-D protocol

To work with the camera, or rather check its functionality, I wrote a simple utility.

When you connect an interface converter to a computer in the computer, a new virtual port appears (depending on the converter). You can connect to it in the program by first setting the port speed required for the cameras used. The program provides the ability to control the camera through command bits, prescribe the message manually and the minimum standard functionality for turning the camera, controlling its zoom, focus and aperture.

The program uses standard settings COM port 8N1 (8 bits, no parity, 1 stop bit). The utility does not control the control lines of the COM port (RTS and DTR).

Code example

An example of implementing a code for controlling a PTZ camera using the Pelco D protocol will look like this:

Unsigned char ptz_camera_adress; // camera address // sending data via the Rs-485 line // input: *data - pointer to the array of data to be sent void ptz_camera_send_data(char *data) ( rs485_mode_send_data(); while (*data) ( send_uart(*data); + +data; ) rs485_mode_received_data(); ) // send a message to PTZ cameras // input: adress - camera address, cmd1 and cmd2 - commands 1 and 2, data1 and data2 - data 1 and 2 void ptz_camera_data_send(unsigned char adress,unsigned char cmd1,unsigned char cmd2,unsigned char data1,unsigned char data2) ( char ptz_camera_txBuff; ptz_camera_txBuff=0xFF; ptz_camera_txBuff=ptz_camera_adress; ptz_camera_txBuff=cmd1; ptz_camera_txBuff=cmd2; ptz_camera_txBuff=data1; ptz_camera_txBuff=data2; ptz_camera_txBuff=ptz_camera_adress+cmd1+cmd2+ data1+data2; ptz_camera_send_data(ptz_camera_txBuff); ) // camera on void ptz_camera_on(void) ( ptz_camera_data_send(ptz_camera_adress,0x88,0x00,0x00,0x00); ) // camera off void ptz_camera_off(void) ( ptz_camera_data_send(ptz_xera_adress,0,0x00); 0x00,0x0 0.0x00); )

rs485_mode_send_data()- switching the Rs-485 module to data transmission
send_uart(char data)- the function of sending data via UART
rs485_mode_received_data()- switching the Rs-485 module to receive data

Connecting a PTZ surveillance camera is in many ways similar to connecting a standard surveillance camera. Most PTZ cameras have three connectors: for power, video and data. You will find audio on some PTZ cameras, but this is quite rare.

First of all, you must correctly determine the power requirements of the camcorder PTZ surveillance. Most of these cameras operate on 24V or 12V DC. You should also check the amperage requirements of the camcorder. Since they have a built-in motor, they consume more current. For example, if a PTZ surveillance camera is specified as 12 V DC / 2 A, you must ensure that it draws at least 4 A of current.

After you have connected the power, now you need to connect the video wires. Often in controlled video cameras for video transmission are used. Many CCTV installers use Category 5 (CAT5) cable to connect to PTZ cameras. Use a paired CAT5 cable for power transmission and a single-core cable for video signal transmission.

If your PTZ camera has audio support, you can connect a pair of audio cables. In many cases, when installing surveillance cameras, engineers use CAT5 cables to transmit not only video and data, but also audio.

The data wires are connected last. Commands are transmitted through them, which, for example, make the camera rotate. RS485 is a very common interface used for data transmission. You can use the joystick or to control the PTZ camera. But you have to check if they are compatible with each other. Most PTZ cameras use the Pelco protocol, and DVRs and controllers must also support it. You must set the PTZ ID, baud rate and protocol.

In order to program PTZ camera may need to open its case. Inside you will find a jumper block, also known as a DIP switch. It can program the PTZ ID, baud rate and protocol. In the DVR settings, go to the main menu, find the PTZ configurations and copy the same values. If you are using a joystick, change the settings using button combinations.

We wish you success in connecting your surveillance camera with Pan Tilt Zoom functions.

Source cctvdvrsystem.co.uk. The article was translated bysite administratorElena Ponomarenko