Application of HD-SDI Camera in CATV Monitoring

1. Background

Security monitoring systems have evolved from analog to digital, from closed to open networking, and the image quality has become higher and higher, entering the era of megapixels, and there is no doubt that products will become more intelligent. These directions are the general trend, and the industry is also happy to face and accept challenges. However, the problem that makes the security control industry headache is interoperability. When the product system specifications of each company are different and cannot communicate with each other, how can an open networking environment be built?

In view of this, PSIA Alliance and ONVIF Forum were launched in 2008, and HDcctv Alliance was established last year, all hoping to establish alliance power and realize the vision of unified monitoring standards. Compared with ONVIF, which has security giants such as Axis, Sony, Bosch, and PSIA, which has strong alliance members such as Cisco, GE, Honeywell and Panasonic, HDcctv Alliance is not well known, and the scale of the standard camp is also relatively small. Chartered members include HD-DSI chip design company Gennum, video codec technology startup Stretch, camera manufacturer Ovii, Taiwan's security system ODM manufacturer EverFocus and CSST.

The HDcctv Alliance was established to upgrade analog CCTV and develop a new standard for high-definition security system applications. HDcctv has published the 0.9 version of the standard. The HDcctv Alliance, the organization responsible for promoting the new standard, hopes to launch cameras using the final 1.0 version of the standard in September 2009 and plans to launch a complete system this year. The new standard originally defined the handshake protocol for exchanging video resolution and frame rate information through HD-SDI links; the HDcctv Alliance hopes that future versions of the standard will also support two-way voice and power through HD-SDI cables. Unlike other camps that call for IP, HDcctv claims to be a convenient way for current analog CCTV system operators to upgrade to HD quality.

Currently, ONVIF, PSIA and HDcctv still have distinct boundaries and play important roles in network and closed-circuit HD respectively.

In terms of network, the most obvious benefit that ONVIF and PSIA bring to network monitoring is the unified standard. ONVIF based on SOAP is more stringent than PSIA based on REST, which can guarantee 100% compatibility, but the latter is more flexible in terms of integration and easier to integrate with other security systems such as access control. At present, ONVIF seems to be more powerful than PSIA because its main members have monopolized almost 60% of the market in network monitoring. But no matter whether they coexist or one party wins in the end, the cost reduction brought by compatibility will promote the faster realization of network monitoring in the next few years.

As for HDcctv (closed-circuit high definition), it relies on its characteristics to capture markets other than large-scale projects, such as markets where the initial wiring is CCTV and needs to be upgraded to high-definition CCTV, or areas that require real-time video monitoring, such as casinos and places that focus on real-time broadcasting. Closed-circuit high definition (HDcctv) takes into account the convenience of analog monitoring and the image quality of network high definition, allowing users to achieve full HD video monitoring in the most familiar environment.

2. Comparison of technical characteristics

As people's requirements for visual effects continue to increase, the clarity of the picture is also constantly improving, and the concept of "high definition" has also been widely recognized. In electrical appliance stores, you can see it everywhere, such as: home high-definition digital cameras, full high-definition LCD TVs, blue-ray DVDs, etc. 1080P and 720P have become a standard for measuring picture quality and are widely accepted.

In the field of video conferencing, since LifeSize launched the industry's first 720P product in 2006, and later Keda launched the industry's first 1080P product, high-definition has long been applied and has become the current main market. In the field of video surveillance, affected by various factors, high-definition has just started. In recent years, since the concept of "high-definition" has become popular in the video surveillance industry, more and more manufacturers have begun to launch "high-definition" products. Looking behind the various types of "high-definition products" on the market, we found that many products have different understandings of the "high-definition" indicators, and the performance effects are also very different. So, what is the concept of "high-definition" in the video surveillance industry?

According to the definitions of the Society of Motion Picture and Television Engineers (SMPTE), the International Telecommunication Union (ITU) and my country's National Radio and Television, there are currently three main formats of true high-definition video: 720P (1280*720 resolution, 16:9 widescreen display, progressive scan/60Hz); 1080i (1920*1080 resolution, 16:9 widescreen display, interlaced scan/60Hz); 1080P (1920*1080 resolution, 16:9 widescreen display, progressive scan/60Hz). Among them, 1080P is the highest level of high-definition video clarity standard.

In this new direction, there are also new requirements for HD cameras. The first is the resolution of the camera. Only HD signal sources can make HDTV show its HD quality, which of course requires a megapixel camera to achieve. However, the concept of "megapixel" is not a recognized standard but only a best practice adopted by the industry. It specifically refers to the number of image sensor elements of a digital camera. Since high resolution is often accompanied by a large amount of image data, this often affects the frame rate. Therefore, a megapixel camera alone cannot guarantee high image quality. In contrast, a network camera that meets any given HDTV standard must be able to provide a certain resolution, frame rate and color fidelity to always ensure video quality. Full HD 1080P is the best choice. The so-called full HD (FULLHD) refers to a physical resolution of up to 1920×1080 display (including 1080i and 1080P), where i (interlace) refers to interlaced scanning; P (Progressive) represents progressive scanning. There is a big difference in the fineness of the picture between the two, and the picture quality of 1080P is better than 1080i. Correspondingly, 720p is called standard HD. Obviously, since the data information is richer during the transmission process, 1080p has more advantages in resolution, especially on large-screen TVs, 1080P can ensure clearer picture quality.

The second is the choice of camera interface. The real high-definition interfaces include HD-SDI, YPbPr, HDMI, and DVI. From the table below, we can clearly see the comprehensive advantages of HD-SDI interface among the current high-definition digital interfaces. At the same time, HD-SDI is the standard interface of the broadcasting and television industry, so it can be said that HD-SDI is the most suitable pure high-definition digital interface.

After years of research on the high-definition video surveillance market and 14 years of experience in the imaging industry, Lingyun has launched a high-definition surveillance camera with a high-definition interface HD-SDI, named Magnolia, which has made a new attempt to connect Chinese machine vision companies with the high-end surveillance industry and has also provided an extremely competitive high-quality product for the closed-circuit high-definition surveillance (HDcctv) field. The following is a comprehensive comparison of the technical parameters of Lingyun's HD-SDI camera and the general high-definition IP Camara on the market:

From the above technical parameters, we can conclude that HDcctv has three major advantages over IPC:

1. Reliability without distortion: Unlike digital surveillance data, which is transmitted over the network in packets after compression, the uncompressed digital data is transmitted on the coaxial cable without distortion. The uncompressed high-definition images provided by HDcctv can provide the best high-definition image source required for intelligent monitoring.

2. HD-level real-time images: It does not generate compression and packetization during the transmission process, and does not cause image delay problems like general digital HD. It is particularly suitable for occasions that require real-time monitoring, such as casinos;

3. Same installation method as CCTV: Use the existing coaxial cable to upgrade from analog to FullHD resolution, just replace the camera and DVR. Compared with switching to IP network monitoring, dealers/engineers do not need to make additional upgrades and learn complex network knowledge; multi-task transmission on coaxial cable: video/two-way audio/two-way control/power can be transmitted simultaneously, saving wiring costs;

As soon as Magnolia was launched, it was fortunate to participate in the Shanghai Pudong New Area Urban Surveillance HD Coverage Project, which is the largest single video surveillance project in China so far and is also the largest HD surveillance project in the world. The project has more than 10,000 surveillance points and adopts HD technology on a large scale, becoming the first large-scale HD surveillance project in the Chinese surveillance market, with far-reaching representative significance. Lingyun Company provided a series of HD surveillance products for it and became one of the HD camera providers, realizing 1080P CCD HD video acquisition, providing strong security guarantee for the World Expo.

However, in the traditional closed-circuit high-definition field, HD-SDI cameras still have a wider range of applications. The following is an actual case to demonstrate the application of HDcctv solutions in CATV monitoring.

3. Application of HD-SDI Camera in CATV Monitoring

CATV is called cable television network, which is operated by cable television companies and provides broadcasting services, including television, teletext, etc. CATV network adopts analog transmission method and is an analog network. Basically, CATV cable is used for broadband transmission. Different from the baseband transmission adopted by other Ethernet physical layers, the broadband wiring system can divide the frequency band into different spectra, and then provide different services through different frequency bands. This technology has been widely used in cable television broadcasting, providing multiple TV channels on the same cable at the same time. Since each channel occupies a different frequency band, they can not interfere with each other.

HD-SDI high-definition camera: Directly output 1080P high-definition format video can be directly connected to the back-end equipment of broadcasting and television. For example, Lingyun's Magnolia is a high-definition camera tailored for ITS and high-end monitoring. In addition to the 3A functions (Auto Shutter, Auto Gain, Auto IRIS) of standard monitoring cameras, it also has the unique function of Auto Gamma. Combined with the camera's own high sensitivity, high signal-to-noise ratio, high dynamic range and other characteristics, it provides a good guarantee for our night image effect and image brightness.

HD-SDI fiber optic transceiver: The transmission distance of HD-SDI is only about 100 meters. The fiber optic transceiver can solve the problem of long-distance transmission. It is also small in size and can be installed in a protective cover together with the camera.

HD encoder: An encoder is a device that compiles and converts signals (such as bit streams) or data into a signal form that can be used for communication, transmission and storage. The amount of data output by HD cameras is very large (1.45Gbps). HD encoders can effectively process huge video data and compress it into H.264 format data that meets the requirements of QAM modulators, which is convenient for the next step of processing.

Stream multiplexer: Multiplex multiple single-program TS streams or multi-program TS streams into a multi-program TS stream containing the contents of these streams. Generally, the multiplexer also provides functions such as mapping and generation of PID, Service ID, Tansport ID, SI, and PSI. Different sources such as MPEG-2, H264 encoding, and other business TS streams can be input into multiple single-program TS (SPTS) streams or multi-program TS (MPTS) data, and multiplexed into one multi-program TS (MPTS) stream. At the same time, it can filter, regenerate and edit the PID of the PSI/SI table of all input programs. And EPGCA and data broadcast information can be inserted into the output stream.

QAM modulator: The working principle of QAM modulator is that the transmitted data is divided into two paths (each with a rate of 1/2 of the original) in the bit/symbol encoder, and multiplied by a pair of orthogonal modulation components respectively, and then output after summing. Compared with other modulation technologies, QAM coding has the advantages of being able to fully utilize bandwidth and strong anti-noise ability. That is, through modulation, a digital signal that can be received and processed by the set-top box can be generated. The QAM modulation and demodulation in digital TV modulates the TS stream by QAM64, that is, modulates the baseband signal of the TS stream onto the carrier, and then sends it to the cable TV network.

HD digital set-top box: The full name of the set-top box is "digital TV set-top box". It is a conversion device that converts digital TV signals into analog signals. It decodes and restores digitally compressed image and sound signals to generate analog video and sound signals, and provides high-quality TV programs to viewers through TV monitors and audio equipment. It adopts a compatible method and has been used in China until now. Therefore, the HD digital set-top box is a conversion device that converts digital TV signals into HD signals. It is generally equipped with an HDMI high-definition data interface, which can present a picture quality of up to 1080P on the corresponding TV.

Government legal institutions, such as courts and procuratorates, as important departments of the country, require not only elegant and comfortable office environments, but also security and reliability. In order to ensure the safety of the building and the fairness and justice of the trial process, to prevent malfeasance in the trial process, and to prevent the escalation of the situation and to control it in time when an accident occurs, the design of closed-circuit monitoring will ensure the safety of the court. As a relatively mature application solution, the radio and television network is very consistent with the special requirements of such places. Through the existing mature optoelectronic equipment for encoding, integration, modulation and other steps, the original monitoring signal can be perfectly transmitted to various networks that meet the radio and television standards, and then the signal can be restored through the decoding of the digital set-top box. For users, real-time monitoring can be as easy as watching TV programs.

At present, we are in the era of image quality revolution. High-definition digital cameras are gradually replacing previous analog devices. For the field of radio and television network monitoring, the IP high-definition network cameras on the market cannot utilize existing resources. If the system is to be upgraded, the entire existing system will be completely changed, which will inevitably lead to increased costs and waste of resources.

High-definition digital cameras with HD-SDI interfaces are very suitable as the first choice for equipment replacement. HD-SDI is a BNC interface in physical form and is also a special interface for the broadcasting and television industry. You only need to replace the encoder and the digital set-top box used for decoding with high-definition ones to form a new high-definition monitoring system. The original cables, modulators, code stream multiplexers and other equipment can be retained, saving a lot of costs. High-definition image quality can better depict the details of the scene being shot, making the monitoring system more perfect and more efficient.