Technology Showcase: PTZ Cameras
Jun 1, 2005 12:00 PM, By Bennett Liles
Remote camera control gives you all the angles.
During the '90s, a couple of new technical trends began to converge in the broadcast industry. Robotic cameras, already familiar in the security business, started making their way into television studios. Remote-controlled camera pedestals and pan/tilt heads matched with shrinking ENG/EFP cameras enabled video engineers to extend their electronic control into what had been the cameraman's realm.
In the decade since broadcast-quality video and remote camera control began to merge, the hardware has continued to shrink while the control options have grown. Now, the Internet and IP control have allowed some of these devices to extend their range from around the building to across the planet.
PTZ cameras (pan/tilt/zoom) have exploded into a vast array of sizes and types, and their uses have expanded similarly. We will have a look at analog PTZ models and a few of the higher-performing digital PTZ types, commonly known as network cameras. The selections in our field have in common remote control of pan, tilt, and zoom functions, 30-frame transmission capability, and analog NTSC output or a maximum digital frame size up to at least 640×480 pixels. Although there is also a plethora of all-in-one videoconferencing systems available, we will examine PTZ camera models as discrete units.
The primary distinguishing factor of PTZ cameras, as the designation implies, is remote control of camera movement and zoom. Analog PTZ models usually rely on an RS-232 or RS-422 control protocol through a multi-pin connector. The protocol used depends largely on the desired control cable length, with RS-422 capable of longer runs up to around 4,000ft.
A widely used control protocol is VISCA (Video System Control Architecture). This is a platform-independent machine control method developed by Sony that can be used to operate up to seven VISCA-compliant devices, such as PTZ cameras on a daisy chain of eight-pin RS-232 cables. Each camera is individually addressable by means of an identifying hardware switch or hexadecimal code assignment. Some models also permit various exposure modes and white balance to be set remotely with VISCA commands. These commands may also be used for controlling monitors, AV switchers, VCRs, and other devices. The protocol is open, and no licensing is required for distribution of VISCA-compatible hardware or software.
The PTZ controller interface may be hardware or software. If on-air shot changes are planned, it might be better to consider a joystick-operated hardware controller. A joystick controller is generally simpler to set up and operate than trying to perform smooth camera moves with a mouse. Most analog PTZ cameras can store six or more separate shots by memorizing the pan, tilt, zoom, and other parameters. Many offer a number of selectable zoom speeds. However, some PTZ cameras change shots with a rather jerky and mechanical movement, more like a security camera. This is one feature that should be evaluated with a first-hand demonstration before buying. For users considering computer control, software can be downloaded from most of the vendors' websites so that potential clients may familiarize themselves with the available options and get acquainted with the look of the graphical user interface.
Eagle Technology E-DC2003
PTZ cameras have adopted most of the features that one would expect to find on “prosumer” camcorders, including various exposure modes and shutter speeds, negative image, reverse video, and image flip for mounting the camera upside down on a ceiling. Some models also offer an “Auto ICR Mode” that switches on or off an internal infrared filter that's dependent on a luminance threshold setting. Under low light conditions, the IR filter can be set to cut off to allow better low-light viewing. Auto power-off may be set to a specific time period. Video muting is also available on some models, sending synchronous black on command.
Some PTZ cameras also feature an auto-track function that will sense an area in the frame that is substantially different in luminance from the background and will activate the pan and tilt to allow the camera to keep that area in frame as it moves. It is wise, however, not to rely on this feature as a substitute for an alert operator.
Handheld, infrared remote controls are also a common accessory, enabling control from the room in which the camera is located. These are very handy for setup. With a local video monitor showing the camera output, one person can stand or sit in various locations and arrange the six or more preset shots with framing, focus, zoom, iris, and other parameters, using the IR remote.
Another spec that many PTZ cameras share is digital and optical zoom capability. As with any video camera with such features, the optical zoom does not noticeably diminish image quality, but the digital zoom, which on some models automatically engages at the end of the optical zoom range, rapidly degrades picture resolution. This is important to remember because the published zoom specification may actually be a combination of both optical and digital zoom ranges.
There are a number of ways in which interconnection can be accomplished between PTZ cameras and controllers. One scheme, touched on previously, is to daisy chain the cameras between the control point and the end camera. This is the preferred method when using the COM port of a computer as an RS-232 control vehicle. Another is to use multiple RS-232/RS-422 ports on a hardware controller to run a control cable directly to each camera. In each case, the control, power, and video are conveyed on separate lines that may be routed differently, depending on the architectural requirements of the setup.
There is another method in which a hardware interface is used on or near the camera mount to translate the power, video, and control signals to Cat-5 unshielded twisted-pair cable normally used for computer networks. At the control end, the computer cable is terminated with another interface that separates the power, control, and video. The decision to use this method is usually a cost-saving measure. Using long runs of more expensive coaxial cable for the video signal is sometimes cost-prohibitive.
The digital PTZ devices commonly referred to as network cameras use a different method of signal conveyance, though they share several primary operational characteristics with their analog cousins. However, there are differences that affect the applications for which they are commonly used. They are frequently called by the PTZ name, so a look at these products may help to clear any confusion.
Not all network cameras have PTZ capability. Like many analog cameras used for security purposes, some digital network cameras are fixed in place and have no remote pan, tilt, and zoom capability. To blur the analog/digital line even more, many network cameras also have analog outputs on a BNC, RCA, or other type of connector for local monitoring or individual recording.
Of course, the big advantage of network cameras is that their video signal and control capability may be extended worldwide via the Internet. Many network PTZ cameras have incorporated web and FTP servers and may be accessed directly by their own IP addresses. However, the IP medium that offers this huge expansion of reach also puts bandwidth limits on image quality. The two primary video compression standards that have been developed to deal with this limitation are MPEG and Motion JPEG.
When transmitting video at 30 frames per second in a frame size and resolution approaching that of NTSC analog video, an IP network intended primarily for office applications has to work pretty hard. Among the methods used to compress the data is Motion JPEG. This is not an actual motion compression scheme but a series of JPEG-compressed still images. This method is a simple way of compressing video signals, but it results in very large file sizes. Due to its relative simplicity, however, it is sometimes the preferred compression method.
The other contender in the game of higher-quality digital video transmission is MPEG-4. This compression method is much more complex than Motion JPEG — it economizes on bandwidth and saves storage space. The tradeoff is that MPEG-4 requires much higher processing power on the receiving end, while a lower need for processing is the primary attraction of Motion JPEG in moving digital video over IP networks. However, the general rise in computer processing power is causing a corresponding increase in the popularity of cameras with MPEG-4 compression. Also, many network cameras are capable of local still image storage through the use of onboard PCMCIA cards.
The crux of the matter is that if economical transmission over vast distance is the main concern, high-quality network cameras excel; but if video quality is paramount and the control/recording point is located in the same building as the cameras, analog PTZ cameras are the way to go. There might also be situations in which both needs are accommodated by running analog cameras into a video server for IP transmission, while using the direct analog signals for recording or local cable distribution. As with many other types of video and sound equipment, the investment should be guided by a clear understanding of the specific job for which the equipment will be used.
Axis Communications 213
Let's have a look at what is available in the incredibly wide and varied field of remote-controlled pan/tilt/zoom cameras.
Among its many network cameras, Axis Communications markets the Axis 213 with the ability to stream Motion JPEG and MPEG-4 simultaneously (with software upgrade). The camera can store 20 preset shots and adds “auto patrol” pre-programmed motion capability. Features also include two-way audio capability (optional Axis 213 CM), two alarm inputs, and three relay outputs. A built-in web server enables direct IP network connection and control through 340 degrees of pan and 100 degrees of tilt. A 26X optical and 12X digital zoom can zero in on objects over a deep field and bring them into sharp focus with auto focus. It can also switch from color to monochrome for low-light situations. The Axis 213 retails for less than $1,700.
Canon offers the VC-C50i with a 26X optical zoom and 12X digital zoom, nine shot presets, 460 TV lines resolution and one-touch automatic/manual white balance. Up to nine VC-C50i units may be cascaded via RS-232C by using the supplied VC-EX3 adapter, which includes an S-Video output and connections for alarm, sensor input, and external light trigger. Low-light video response goes down to 1 lux, and IR illumination is built-in and effective for objects up to 9.8ft. away. Pan range is 200 degrees, and tilt range is 120 degrees. The ceiling-mount model will pan through 340 degrees. A 1/4in., 340,000-pixel CCD generates the video signal. The unit weighs less than 1lb. and retails for about $900.
Also from Canon is the VB-C50i network camera. The product numbers here are very similar with those of the analog VC-C50i listed previously. This camera has the same 26X optical/12X digital zoom. The unit has built-in web and FTP servers for direct Ethernet connections to up to 20 PCs simultaneously by way of an RJ-45 jack on the body. Output resolutions range from 160×120 to 640×480. Maximum pan is 200 degrees, with 120 degree as the max tilt. The reverse-mount VB-C50iR extends the pan range to 340 degrees with a tilt of +10/-90 degrees, and up to 20 preset shots can be configured. With the optional VB-EX50 expansion box, analog outputs, RS-232C control, and sensor outputs are possible. The product retails for less than $1,500.
Eagle Technology of Cape Town, South Africa, markets the E-DC2003 indoor PTZ videoconferencing camera with 12X optical and 10X digital zoom, 420 TV lines resolution, and 1 lux minimum illumination. The unit features auto/manual white balance, shutter speeds from 1/50 to 1/10,000 second, signal-to-noise ratio of more than 48dB, and a pan-tilt range of ±160 degrees. Among the company's network camera products is the E-VPT3122 mini pan/tilt network camera with integrated MPEG-4 compression engine and IP server for 10/100 Base T Ethernet output. The camera can accept an external microphone and includes an analog video and audio output, 256-bit web encryption, video time/date stamp, alarm in, and relay output. The E-DC2003 lists for $1,660, and the price of the E-VPT3122 is $484.
Long known for its presentation products, Elmo Manufacturing of Plainview, N.Y., also offers a wide selection of CCTV cameras. Among these is the PTC-400C. With a 12X optical and 16X digital zoom, 350-degree pan, 210-degree tilt, IR remote control and RS-485 daisy chain control connections for up to 223 cameras, the PTC-400C can fill many roles. Sixteen position presets are programmable, and there is auto/manual control of eight pan/tilt speeds. The unit provides a power-save mode and a handy auto-return to home position. The camera retails for less than $800.
Among the network camera products from JVC is the VN-C30U for 10/100 Base T Ethernet networks. With MPEG-1 and JPEG compression, the camera provides a 15X optical zoom, auto/manual focus, 10 preset shot positions, and up to 30fps frame speed. The constant bit rate is user-selectable for easy network traffic management, and DHCP simplifies initial network setup. Minimum illumination is 2.5 lux, and the camera moves through 320 degrees of pan and 90 degrees tilt. The product lists for as little as $1,250.
While a good many manufacturers have chosen to specialize in either network or analog PTZ cameras, Sony has made a significant investment in marketing both types. Among the analog products, the EVI-D70 has established a strong presence. The VISCA-controlled EVI-D70 features an 18X optical and 12X digital zoom, EXview HAD CCD for improved low-light imaging, 470 TV lines of resolution, auto ICR function, auto power off, six shot presets, and a handheld IR remote commander. The product has a capability for RS-232C daisy chain operation with up to a total of seven units on the chain. The EVI-D70 also has an alarm function that can detect changes in luminance level within a user-designated 16×16 pixel area. Also featured is image flip for ceiling mounting and auto or manual white balance. The EVI-D70 may be controlled through a computer software application or by a hardware joystick controller unit marketed as the RM-BR300. The product is available in white or black finish and lists for just less than $1,000.
A notable Sony entry in the field of network cameras is the SNC-RZ30N. This product features selectable frame speeds up to 30fps (with adequate processing at the receiving end), selectable JPEG compression ratio between 1/5 and 1/60, and selectable resolution from 160×120 up to 736×480. The SNC-RZ30N may be operated on Mac or Microsoft Windows 98, 98SE, ME, NT 4.0, 2000, and XP with Internet Explorer versions 5.5 or 6.0. The zoom range is 25X optical and 300X digital. The camera offers a 340-degree pan range and -90 degree to +25 degree tilt range. Included is a rear-mounted BNC connector carrying analog output. On the base is a two-slot PCMCIA device for inclusion of local hard drive or flash memory for still storage. Also included are motion detection and an internal web server. The network hardware interface is RJ-45. The unit retails for around $1,400.
The PT3122 from Vivotek is a network camera featuring an MPEG-4 compression engine on 10/100 Base T Ethernet through an RJ-45 connection. The camera can use its own internal microphone or accept an external mic on a rear mic jack. Also included on the rear chassis is an analog AV output. The unit features an I/O connection block for sensors and alarms, and 270-degree pan and 170-degree tilt. With IP addressing, the digital video output is viewable directly on a web browser from anywhere. The PT3122 is available for around $650.
These are but a few examples in the huge array of analog and digital PTZ cameras currently available. Most have the same basic features, but it pays to compare closely for those extra functions that will be just right for your specific application. With the current state of competition, it is a sure bet that with careful shopping, there will be one with just the right features at the right price.
For More Information
Once the sole domain of analog cameras and coax cable with limited range, the security field has become an enormous opportunity for makers of IP cameras. Their basic advantage is that with Internet connectivity, there is no physical limit to their links of transmission and control. Combined with easy IP setup and output adjustments to suit network traffic constraints, network cameras can keep an eye on anything just about anywhere, all the time. Any of the network cameras mentioned here can be used quite effectively in a security role. Quite a few are marketed specifically for this — collectively, they're known as “dome cameras.”
Most have features especially suited to security applications, such as motion detection, auto-tracking, automated panning/tilting functions, and alarm outputs and inputs. Many surveillance systems can use these triggers, so that whenever there is motion detected by a specific camera, that unit's signal is switched to the recording device. External alarms can activate cameras in specific areas in response to events there. Coupled with digital time/date recording, a specific event occurring within a known range of time can be located and reviewed quickly.