The high-definition wave of video surveillance is unprecedented and repeated, and product planning needs to find reliable technical solutions. Although the pure IP surveillance camp is like fish in the water, the products are threatening, and the food sharing opportunities and expansion fields may not be able to dodge, but if they are more transparent and transparent, they will be more confident to meet the challenge. Today, no one can overwhelm the victory, knowing each other's strengths and weaknesses, you can quickly cut into a suitable survival position. HD-SDI is a way out for traditional CCTV ..
The test of IP photography is often not transmission, because IT Netcom itself is a mature field, but the image quality is most easily criticized. As for the HD-SDI monitoring system, the key is not just the image, but the transmission. High-end photosensitive components and image processing components are almost at your fingertips, but how to use the right components to maintain high image quality transmission and ensure long-distance distortion-free is a matter of knowledge.
Feeling struggling when the distance is long
The picture is clear, there is no delay, convenient control and remote storage management, it is easy to say, but after high-definition becomes a problem. Regardless of whether the high-definition image is compressed, how fast and instantaneous the non-networked image signal can be transmitted, and how far it can run, is a very harsh test for security monitoring. So we say that the test of high-definition is transmission, and the farther it is, the more dangerous it is. As we are familiar with SDI, the concept of its specifications does not come from the field of imaging, but refers to a transmission method, which is the technology of signal transmission and reception (Tx and Rx).
The concept of Datacom, which is popular in recent years, is very different. The method of directly transmitting HD images without IP network architecture is rapidly burning in the field of CCTV.
Since the HDcctv alliance led by Gennum and Stretch was ignited in 2010, HD-SDI has become an important learning center in security manufacturing.
All of a sudden, the renewal of concepts, the hardship of research and development, and the hope of killing the Red Sea are intertwined and intertwined in the process of HD security. For the CCTV ethnic group, whether HD is easier or actually harder is a difficult topic to answer. Including device compatibility, image signal purity, transmission distance, low latency requirements, back-end compression efficiency, image analysis performance, power supply, control signals, interface with IP networks, display playback formats, and even The cost of electronic materials is already a great test. In the end, there are several solutions to realize SDI on the market? What related technologies should be available? What alternative HD architectures besides SDI? Is real-time imaging the only requirement? Are there opportunities for optical fibers or other wires? Various doubts about the development of HD systems, We cross through the discussion of Tx and Rx.
SDI function consists of different units
The SDI chip solutions we have seen in the security R & D circle today, even including FPGAs, have been formed as early as 2007. At the media exhibition in the United States (NAB2007) at that time, the chip makers launched many solutions for 3G-SDI (third-generation serial digital interface). These companies include Gennum (now incorporated into Semtech), National Semiconductor (NS, now incorporated into Texas Instruments), Altera and Xilinx.
Among them, Gennum has developed the GV7600 / GV7601 chip in security in the future. In addition to being the main driving force of HDcctv, it is also the first to integrate discrete chip architectures such as Tx and Rx into one. For example, the chip at the transmitter (Tx) is the serializer (Serializers) plus cable drivers (CableDrivers), and the chip at the receiver (Rx) is the deserializer (Deserializers) plus cable equalizers (Equalizers) Can simplify the design of the camera and DVR.
Xu Wenlong, the current business manager of Semtech Asia Pacific, said: "Because the success of our chip comes from the affirmation of the broadcast and television field, there will be many customer research and development units, and we will use the GV7600 and GV7601 that we published in security applications in other related fields such as TV Walls, medical endoscopes, MachineVision, etc. "
In fact, for example, adapters and Extender devices that extend HDMI signals to more than 100 meters can indeed play well. This explains the quality capabilities of SemtechCanada (Gennum) chips to a considerable extent. In the future, SemtechCanada will also publish new chips based on the existing security application chips, such as a solution for transmitting control signals, sounds and other data from the monitoring end to the camera end through the same coaxial cable.
From the perspective of technical disassembly, the full name of SDI is a serial digital interface, which is a series of formats defined by SMPTE (The Society of Motion Picture and Television Engineers) film animation and television engineers association. This SDI standard serial interface is used to transmit uncompressed and delay-free digital video signals, and can also be embedded with Audio audio and Data control codes. There are currently five kinds of SDI standards, among which HD-SDI of SMPTE-292M standard is mainly used for digital video interface of broadcast video. It transmits 720P and 1080i picture formats at 1.485Gbit / sec.
In addition, there is also a high-definition clear TV definition format commonly known as 3G-SDI adopting the SMPTE424M standard specification, which can provide a high-speed video data transmission interface of 2.970Gbit / s for 1080P.
In security applications, HD-SDI and 3G-SDI are mostly used. To achieve this transmission architecture, in addition to the coaxial cable (including the receiving end equipment) and the BNC connector, it is mainly composed of several components. Introduced by TI (NS) to introduce various chip types, including cable equalizers (Equalizers), cable drivers (CableDrivers), clock reformers (Reclocker), serializers (Serializers), and deserializers (Deserializers) , Video Timing Controller (VideoTiming) and other ICs with special control functions. This means that in the SDI chip camp of HD security, it is roughly divided into two types of integrated types such as Semtech (Gennum) and TI (NS) discrete type. The rest launched separate components, as well as companies such as EqcoLogic and Mindspeed.
SDI chip integration affects design
As for another method of distinguishing SDI chips, especially in security, the difference between single-channel and multi-channel is mainly referring to whether there are four-channel integration in high-speed deserializers. At present, there are four-way solutions, most of which are carried by FPGAs, such as Lattice, Altera, and Xilinx; even if there is a single chip that integrates HD-level MUX and 4-way deserializer from SiliconGear in Korea, it is still the essence of FPGA. . As for when ASICs can really have 4-way in one, maybe when the market becomes more stable and mature, some old security chip manufacturers will launch products. In particular, Equalizers are not suitable for multi-channel integration, which involves too dense circuit wiring and interference.
In addition, SDI includes components such as CableDriver and Equalizer, which all contain mixed-signal technology. Before being incorporated into Texas Instruments (TI), NS was a well-known analog chip supplier. As we all know, TI originally had a strong support force for the security IP camera and the main control chip of DVR / NVR equipment in digital solutions, including DSP / SoC and many other aspects, and played an index role in the security industry. In addition to the integration of NS, TI's overall analog chip strength is strengthened. In fact, the design of HD security is more meaningful.
In April of this year, CompoSec (the 4th Global Security Electronics Technology Forum), Texas Instruments ’lecturer in charge of SDI products, senior application engineer Zeng Xianghua, has already announced the integrated design of front-end and back-end analog and digital chips. TI has been able to target uncompressed HD The camera and HD-DVR propose a more holistic solution to make the introduction of the new architecture smoother.
TI (formerly NS) various SDI components cooperate with streamlined FPGA, and Semtech (formerly Gennum) SDI chips extend the transmission distance and simplify system design, and continue to compete in security applications since 2007.
Just looking at the SDI technology field, the various ways of implementing HD transmission through IC semiconductors have obviously presented a variety of appearances; of course, many people have discussed such high-quality signals, or may use HDMI or DVI channels For example, it is not appropriate to define this uncompressed high-definition scheme with HD-SDI alone. Based on signal format transmission and convenient construction and substitution, SDI connectors such as BNC are the most beneficial for monitoring applications, and are relatively widely adopted, and have become a standard format strongly promoted by the HDcctv alliance.
HDcctv and the test of long distance
At present, "short transmission distance of HDcctv" is one of the problems often raised by many security engineering companies. Even if it uses coaxial cable, it can only be approached 150 meters, which makes system equipment manufacturers still have to provide extension and relay equipment (Repeater) , Which must be built in Tx and Rx, that is, SDI chip, if you add power supply and control signals, it is easy to increase the cost.
Xu Wenlong said: "According to the needs of the security industry, there is a special modification of Rx to GV7601A, which can provide an additional 60 meters of transmission distance compared to the previous version, a total of 200 meters away."
For the SDI transmission supporting solution, some engineering terminals have flexibly used optical fiber to transfer, extending the transmission distance. This direction of consideration directly forms a new opportunity for fiber optic materials and modules in security. From this year's CompoSec Security Electronics Exhibition, you can also observe the wind phenomenon. At present, some system manufacturers have begun to pay attention to this problem. In addition to actively developing new 3G-SDI products and increasing the transmission distance of SDI at the transmission rate, they also choose FPGA design architecture to design HD-SDI Tx chips.
For example, Dirac image compression technology can be used to achieve lossless compression (lossless compression) without relay transmission, and the maximum distance can reach 300 meters of performance.
It can also deliver uncompressed original image signals up to 150 meters (or within the same 150 meter limit), and also includes the HDbaseT solution recently promoted by the Israeli IC design company Valens Semiconductor.
What is special is that it does not transmit through HDMI, does not use coaxial cables like SDI, nor does it pass through LVDS interface circuits, but transmits through the most common cat5e / cat6a network cable (LANCable), which is us Very familiar RJ45 network connector. At present, the first wave launched a pair of Tx and Rx chips, and stated that it was developed for security applications. It can deliver uncompressed and high-quality 1080P @ 60fps images, and the maximum delay of 150 meters is only 10 microseconds.
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