What are the transmission solutions for HD?

The wave of HD security surveillance is rising again and again, and product planning needs to find reliable technical solutions to support it. Although the pure IP surveillance camp is like a shark in the water, its products are threatening, and it is not necessarily possible to dodge the business opportunities and expand the field, but if you can see more clearly, you will be more confident to deal with the challenge.

In today's world where no one can win, understanding each other's strengths and weaknesses will enable you to enter a suitable survival position more quickly. HD is a transformation way out for traditional CCTV. This time we will focus on HD transmission.

The test of IP photography is often not in transmission, because IT network communication itself is a mature field, but the image quality is the most likely to be criticized. As for the HD security control system, the key is not only in the image, but in the transmission. High-end photosensitive components and image processing components are almost readily available, but how to use the right components to maintain high-quality transmission and ensure that there is no distortion over long distances is a science. It

becomes difficult when the distance is extended .

Clear images, no delays, convenient control and remote storage management are all easy to say, but they become difficult after HD. Regardless of whether the HD image is compressed or not, how fast and real-time the non-IP networked image signal can be transmitted, and how far it can reach, is a very severe test for security monitoring. So we say that the test of HD is transmission, and the farther it is transmitted, the more dangerous it is. As we are familiar with SDI, its specification concept does not come from the field of images, but refers to a transmission method, which is the technology of signal transmission and reception (Tx and Rx).

Different from the popular IP monitoring Datacom concept in recent years, the method of directly transmitting HD images without going through the IP network architecture has quickly spread in the CCTV field.

Since the HDcctv Alliance led by Gennum and Stretch was ignited in 2010, HD-SDI has become a prominent school of thought in security control manufacturing centers such as Taiwan, China, and South Korea. For a while, the concept of updating, the difficulty of research and development, and the expectation of breaking out of the red ocean were intertwined and entangled in the process of HD security control. For the CCTV community, whether HD is easier or more difficult is a difficult question to answer. Including equipment compatibility, image signal purity, transmission distance, low latency requirements, back-end compression efficiency, image analysis performance, power supply, control signals, interface with IP network, display playback format, and even the cost of electronic materials itself, all of which are great challenges. How many solutions are there to implement SDI? What related technologies should be possessed? What HD alternative architectures are there besides SDI? Is real-time image the only requirement? Is there any chance for optical fiber or other cables?

We have overcome all kinds of doubts in HD system development through the discussion of Tx and Rx.

SDI functions are composed of different units

. The SDI chip solutions we see in the security control R&D circle today, even including FPGA, have been formed as early as 2007. At the American Media Expo (NAB2007) at that time, chip manufacturers launched many solutions for 3G-SDI (third-generation serial digital interface). These companies include Gennum (now merged into Semtech), National Semiconductor (NS, now merged into Texas Instruments), Altera and Xilinx. Among them, the GV7600/GV7601 chip developed by Gennum later became famous in security control. In addition to being the driving force of HDc ctv, it was also the first to integrate discrete chip architectures such as Tx and Rx into one. For example, the chip of the transmitter (Tx) is a serializer plus a cable driver, and the chip of the receiver (Rx) is a deserializer plus a cable equalizer, which can simplify the design of cameras and DVRs. Xu Wenlong, current Semtech Asia Pacific Business Manager, said: "Because the success of our chips comes from the recognition of the broadcasting and television field, many customers' R&D units will use our GV7600 and GV7601 for security applications in other related fields such as TV walls, medical endoscopes and Machine Vision. In fact, for example, adapters and Extender devices that extend HDMI signals to more than 100 meters can really perform well." This is a considerable comment on the quality capabilities of Semtech Canada (Gennum) chips. In the future,

Semtech Canada will also successively release new chips with additional functions based on existing security application chips, such as solutions for transmitting control signals, sound and other data from the monitoring end to the camera end through the same coaxial cable.

From a technical perspective, SDI is the full name of Serial Digital Interface, which is a series of formats defined by SMPTE (The Society of Motion Picture and Television Engineers). This SDI standard serial interface is used to transmit uncompressed and delay-free digital video signals, and can also embed Audio and Data handles. There are currently five SDI standards, among which HD-SDI of SMPTE-292M standard is mainly used for digital video interface of broadcast-level video, which transmits 720P and 1080i picture formats at 1.485Gbit/sec.

In addition, there is also a high-definition television definition format commonly known as 3G-SDI, which adopts SMPTE 424 M standard specification, and can provide 2.970 Gbit/s for 1080P high-speed image data transmission interface. In security control applications, HD-SDI and 3G-SDI are mostly used. In order to realize this transmission architecture, in addition to coaxial cables (including in the receiving end equipment) and BNC connectors, it mainly relies on several components. TI (NS) has launched various types of chips, including cable equalizers, cable drivers, reclockers, serializers, deserializers, video timing controllers, and other ICs with special control functions. This means that in the HD security and control SDI chip camp, there are two typical types, such as integrated types such as Semtech (Gennum) and discrete types such as TI (NS). Other companies that have launched discrete components include EqcoLogic and Mindspeed.

The integration degree of SDI chips affects the design

As for another way to distinguish SDI chips, which is particularly obvious in security control, it is the difference between single-channel and multi-channel, which mainly refers to whether there is a 4-channel integration in the high-speed deserializer (Deserializers). Currently, most of the solutions that can have 4 channels are provided by FPGA, such as Lattice, Altera and Xilinx; even if a Korean company like SiliconGear has developed a single chip that integrates HD-level MUX and 4-channel deserializers, it is still FPGA in nature. As for when there will be a real ASIC that is 4-channel in 1, perhaps when the market is more stable and mature, some old security control

chip manufacturers will launch products. In particular, equalizers are not suitable for multi-channel integration, which involves problems such as overly dense circuit wiring and interference.

In addition, SDI includes components such as Cable Driver and Equalizer, all of which contain mixed signal technology. Before being incorporated into Texas Instruments (TI), NS was a well-known analog chip supplier. As we all know, TI already has strong support for security IP cameras and DVR/NVR equipment main control chips in digital solutions, including DSP/SoC, and plays an indicative role in the security industry. The merger with NS not only strengthens TI's overall analog chip strength, but also has special significance for HD security design. In April this year, at the CompoSec (the 4th Global Security Electronics Technology Forum), the speaker of Texas Instruments' SDI products, senior application engineer Zeng Xianghua, had already announced the integration

design of front-end and back-end analog and digital chips. TI has been able to propose a more holistic solution for uncompressed HD cameras and HDD VR, making the introduction of the new architecture smoother.

TI (formerly NS)'s various SDI components are combined with streamlined FPGAs, and Semtech (formerly Gennum)'s SDI chips are continuing their competition in security applications since 2007 in terms of extending transmission distance and simplifying system design. If we only look at the SDI technology field, we can see that various ways of achieving HD transmission through IC semiconductors have already presented a diverse appearance; of course, many people have also discussed that such high-definition signals may use HDMI or DVI channels, and it is inappropriate to define this uncompressed high-definition solution as HD-SDI alone. Zhang Xingfu, a senior consultant of "Security & Automation Magazine", said that based on signal format transmission, convenient construction and substitutability, SDI connectors such as BNC are most beneficial to monitoring applications, and are relatively widely adopted and become a standard format that the HDCCTV Alliance is vigorously promoting.

HDCCTV and the test of long distances

In general, "HDCCTV has a short transmission distance" is one of the problems often raised by many security engineering companies. Even if coaxial cables are used, they can only be close to 150 meters. This requires system equipment vendors to provide extension and relay equipment (Repe ater), which must have built-in T x and R x, that is, SDI chips. If power supply and control signals are added, it is easy to raise costs. Xu Wenlong said: "In response to the needs of the security control industry, we have specially modified the R x to GV7601A, which can provide an additional 60 meters of transmission distance compared to the previous version, and a total of 200 meters."

For the SDI transmission supporting solution, some engineering departments have flexibly used optical fiber to transfer and extend the transmission distance. This consideration direction directly forms a new opportunity point for optical fiber materials and modules in security control. From this year's CompoSec security control electronics exhibition, we can also observe the wind. Zhang Xingfu said that some system manufacturers have begun to pay attention to this issue. In addition to actively developing new 3G-SDI products to increase the transmission distance of SDI with transmission rate, they will also choose FPGA design architecture to design HD-SDI Tx chips. For example, Dirac image compression technology can be used to achieve lossless compression without relay transmission, and the longest distance can reach 300 meters.

The HDbaseT solution recently promoted by Valens Semiconductor, an Israeli IC design company, can also transmit uncompressed original image signals up to 150 meters (or within the 150-meter limit).

The special feature is that it is not transmitted through HDMI, nor does it use coaxial cables like SDI, nor does it use LVDS interface circuits, but is transmitted through the most common cat5e/cat6a network cable (LANCable), which is the RJ45 network connector we are familiar with. Currently, the first wave of a pair of Tx and Rx chips are launched, and it is stated that they are developed for security and control applications. They can transmit uncompressed and high-quality 1080p@60fps images, and the maximum delay of 150 meters is only 10 microseconds.

HDbaseT uses network cables as audio and video signal cables

. Using network cables to run high-definition audio and video signals is of course new, just like our DVD or BD blue-ray players, and even the peripherals of handheld devices connected to TV screens, all use network cables as signal cables. The penetration of network-related technical forces should not be underestimated, but it is rare to play in this aspect.

As early as 2010, the HDbaseT Alliance challenged the HDMI interface with its five-in-one functions of power, control signal, network information flow, audio, and high-definition, so it can be conveniently regarded as HDMI with a network cable. In addition to Valens Semiconductor, LG, Samsung, and Sony are also core members, and it is not difficult to feel their ambition.

With the precedent of the SDI solution, HDbaseT is now more confident in promoting the solution to the security control market. Valens Asia Pacific Director Lin Haoyuan said: "Our biggest competitor is ourselves! While other solutions have been working hard for the transmission efficiency of HD images, VS020 has just started, but it has already produced an inherent advantage in terms of specifications."

Return to the essence of security control design

In addition to choosing a solution, there are several alternative technologies for security control that can be eliminated first to avoid unnecessary R&D and application obstacles.

The first is the cumbersome settings of TCP/IP between the camera and the storage device. Does high-definition image quality have to be achieved through network equipment?

What is the impact of image compression work on the front end? Where and in which data format is image analysis performed?

The above-mentioned HD transmission chip supplier has demonstrated the high-speed link solution of uncompressed images. However, if we care about the security control engineering end, we will definitely notice that the above ideal solution has a new threshold: real-time uncompressed (RAWDa ta) transmission! To fully implement this demand, it is not easy to achieve by simply replacing the cost of high-quality cables.

HD images are indeed a product trend in security monitoring, and they are irreversible; but what are HD images? "Uncompressed" must not be in the definition, otherwise the DVDs, Blu-ray discs, online videos, and even HD-level network cameras we have seen are not qualified to say that they are high-definition, because these sources are all compressed.

ccHDtv uses digital TV technology to transmit security images

Songhan Technology Product Manager Tu Zongxian said that he believes there must be a new design momentum, which comes from the demand for HD images and takes into account the convenience of transmission and management. There is no need to make laborious changes during online deployment, just like the intuition and trust accumulated by the industry between analog cameras and DVRs. There is no need to spend extra relay transmission costs, moderate compression processing can be allowed, and it is also convenient for IP network architecture integration.

也许，我们可以期待这样的安控摄影解决方案，会是新一波投入安控的IC设计产品发表重点。说到台厂的IC，切入HD安控提供Tx和R x最亮眼的代表，从2012年看过来，应该就是I T E联阳半导体，以及他们推动的ccHDtv架构。他们不但完全实现上述HD和非IP架构的描述，而且藉用他们在数字电视领域累积的经验，所提出技术本质为DVB-T的方案，即可实现用同轴电缆「串接」和「并接」等方式拉回储存端管理，确实节省了布线成本耗损。透过「多对一」和「一对多」灵活的分流管理，为HD安控领域注入鲜活的研发方向。

也许有人发现，这样的架构在安控或许是新鲜的，然而在第四台业者、数字电视(尤其是欧洲地区)早已行之多年。而车内收看的电视频道，就是透过DVB-T无线传输。这意味HD无线化的可能性，也是ccHDtv的架构优势。联阳半导体的资深营销经理赖胜中说：「无线化或许在台湾有频道管理上的考虑，但若是在闭路系统中，完全就没有这层法规和安全性顾虑。」这说法蛮务实贴近安控的系统工程实况。他补充：「建置在摄影机尾端的Tx芯片，是参考各方看法和需求性，为安控开发的全新IC，盼望使台湾产业拥有坚实而创新的方案。」

当我们再次聚焦HDcctv的HD-SDI各种芯片架构，包括FPGA、分离型、整合型芯片;参考了走上网络线的HDbaseT，并且有多任务能整合优势;再回看台湾推动的ccHDtv架构，藉DVB-T的成熟技术运用于安控;很显然，安控对HD影像的需求是不言可喻，并且一直将非IP化列为其中一种必要的设计考虑。

不论我们是走在哪一种设计路线，盼望都伴随一条能开创应用形态，同时也有源源不绝技术支撑的源泉。