Vibrant Video Logistics

  

click here to read the original article in ProSystems Africa News 

The term ‘plug and play’ has been around for decades and mostly pertains to the ease of use of technology systems. It’s especially appealing to non-technical consumers prior to opening the box of a new technology-related product. But, at least for the AV professional, it’s often a different story. Video communication is literally stealing the show in the modern age - from marketing platforms to information management and entertainment. For the viewer, it’s as simple as pressing a button and selecting what to watch, or even watching whatever is already displayed. The intricate part, however, is delivering the content from the source to the screen – a process unseen by the user. This has been the cause of many a grey hair for the AV professional. Video distribution has its limitations, which need to be known when designing signal distribution systems. As technology develops, new signal types also come with new challenges.

The most common signal type used in current day video is HDMI (High Definition Digital Media Interface) because of its diverse design. With the introduction of high definition satellite television to the residential market, digital video connection between source and screen was done with HDMI. It was a simple, fresh and effective new component that arrived with the whole new world of high definition television. In fact, HDMI was developed to carry a variety of signals in a single cable. This primarily includes a video component, which is capable of transporting video signals in extremely high resolutions, and an embedded digital audio signal that delivers adequate audio information for the most recent surround sound variants. These two components are sufficient to deliver a comprehensible video signal, but HDMI technology exceeds this by far and additional information is available on the same cable infrastructure

Thus, over and above the audiovisual components, HDMI 1.4 includes an Ethernet channel, enabling high-speed, bi-directional network connectivity at up to 100 Mbps. Display resolution is recognised with EDID (Extended Display Identification Data), which is available to identify the native resolution of a display as soon as it is connected to a video source. The source component will respond by transmitting the content in the optimum resolution that the screen is capable of receiving. In most cases it will be full HD (1920x1080) or, these days, even UHD (3840x2160). Challenges include, for example, sending a full HD signal to a WXGA projector with a native resolution of only 1280x800 – which would be incapable of displaying the complete pixel space of the source image. In this scenario, one of two adjustments can be made to display the content. Ideally, the display device would scan convert (downscale) the image to match its own native resolution. If this is not possible, the source device would reduce its own output resolution in order to meet the display. The latter is not ideal for networked video distribution systems, as the source content’s quality would then be reduced on all connected displays - regardless of their capability to meet a higher definition video.

HDCP (High Bandwidth Digital Content Protection) is the main element behind the development of HDMI as a standard video format. For decades, Hollywood producers have been fighting the piracy war in spite of content duplication being legally prohibited. It has always been a losing battle as there is no effective way to prevent consumers from duplicating analogue video. In a digital world, many parameters can be introduced to a signal to only allow duplication when certain criteria are met. HDCP did exactly that by creating a standard that couldn’t be legally duplicated unless all components in the particular system conforms to a licensed process. Law enforcement is much easier when all stakeholders in the video supply chain are forced to conform, instead of just the end consumer. HDMI’s trump card is that the source component will not transmit a video signal unless a digital handshake takes place to confirm that the display device is licensed as well. Recording equipment will not tick all the required boxes and hence remain unlicensed. A source device will thus not release a video signal connected to a recording device. In layman’s terms, HDCP prevents the digital signal flow unless the display device is HDCP compliant. With economic pressure, the manufacturers of video players and displays are very eager to license their products to avoid paying the price of non-compatibility. Unfortunately, there will always be electronic devices on the black market that override these parameters.

CEC (Consumer Electronics Control) is another feature of HDMI which enables users to control multiple connected devices with a single control interface. A DVD player, for example, can be controlled via the connected HDMI feed, or a third-party control system can control sources and display devices from a single user interface. With all the above components forming part of the HDMI signal, bandwidth requirements are clearly extensive and, as a result, distribution distances are limited. A full HD signal should not be distributed farther than 15m. In a standard residential dwelling this will be adequate, but in larger residences and in professional systems especially, the distribution becomes a challenge. Cables are available at lengths of up to 22m and will work well with lower resolutions, but this might be problematic as the bandwidth increases. In these larger systems even 22m cables won’t be adequate to distribute signals to all displays.

With these distance limitations, an entire new world of opportunities has opened up. Many technologies are available to distribute HDMI - each with unique architecture and challenges. There are balun transmitter- and receiver sets that distribute the HDMI signal components over twisted pair cables, and HDBaseT that uses the same infrastructure but also transmits additional signals such as control protocols and even low voltage power supply on the same cable. Fibre optic mediums are positioning themselves amongst these technologies and, although expensive, are capable of transmitting digital signals across longer distances.

The latest technology breakthrough to see the light is based on the IP infrastructure available in everyday IT networks. These two technologies are encroaching on the other’s territory as they improve. The challenge has always been that the available bandwidth in current day networks is far too little for the vast number of data packets of a video signal. Many compression techniques bridge the gaps and higher bandwidth networks are available, but the latter adds an extra zero to the price tag. Despite all these red flags, Video over IP technology adds a fresh new dynamic to video distribution systems by replacing the conventional video router or switcher with a network switch. True to IT network architecture, video inputs and outputs can be connected at any patch point across the network and routing takes place based on IP addresses. Because video signals can be distributed as IP packets, wireless systems are also seeing the light of day - but many creases still need to be ironed out. It will happen eventually, it’s just not possible to say exactly when.

Video distribution, from small to large systems, may have given consultants and technicians many a headache in this exciting industry. But, luckily, almost always with a happy ending.

The Pixel Age

The most common and primitive method of video signal transmission is between any illuminated object and the human eye. Light from the sun, or any alternative source, reflects off an object towards us at, well, the speed of light. In today’s digital world, littered with video streaming wherever we turn, things happen, rather, at the speed of data packets.

Analogue signals will never be conquered by the digital world. This is based on pure physics. Analogue light and sound waves exist all around us, mostly without human interference. Another reason why we’ll always need the analogue spectrum is because humans are analogue beings. Our eyes and ears receive analogue waves in order to see and comprehend, and our vocal cords produce analogue vibrations for us to be audible. In fact, any digital communication device in the modern world requires A-D (Analogue to Digital) and D-A conversion at either ends of the system to make it usable for human beings. The digital part is purely the technology used to transport the information between end-points without quality loss.

Media streaming is nothing new. The most prevalent example of streamed video and audio is probably from the popular website, YouTube. Many other web services are also using the World Wide Web to distribute video content. Video streaming is however not limited to internet connectivity, and there are many applications which require video distribution over Local Area Networks (LAN) or Wide Area Networks (WAN) in an IP, point-to-point, or multipoint network. The conventional way to distribute video is over copper-cabled systems. From elementary Radio Frequency (RF) networks, to higher resolution video formats such as RGBHV (Red, Green, Blue, Horizontal, Vertical), commonly (and incorrectly) termed VGA signals. When digital video technologies surfaced, they brought along High Definition (HD) resolutions and formats such as HDMI (High Definition Media Interface), DVI (Digital Video Interface), Display Port and SDI (Serial Digital Interface), with the latter still being distributed on RG59 coaxial cable. Parallel to the digital video technology development, Information Technology (IT) also took off at a breakneck pace.

When an image is displayed optically with an overhead or slide projector, for example, the image is created from light projected through a filmstrip and a lens onto a distant surface, which then magnifies every little bit of detail showing perfect lines and curves. In order to reproduce the same image digitally, one would have to subdivide the entire frame in tiny blocks (pixels) and colour them individually to form a pixelated image. The more pixels used in the frame, the better the image quality will appear, but theoretically it’s impossible to produce a perfect curve by using square pixels. Even when the pixels are so tiny that the human eye cannot differentiate between them, a curve may appear smooth, but, in fact, it will always consist of tiny squares. Therefore, higher definitions are the best way to produce quality digital video images.

In order to convert the information of one digital pixel, the analogue wave is plotted on an X and Y axis and broken up into various samples, at a specific sample rate. The metric coordinates of each sample are then converted to a binary system – a numerical system that only utilises ones and noughts and most commonly uses eight digits simultaneously to represent any number between nought and 256. Each digit is known as a ‘bit’, and in the most generally used 8bit networks, eight bits equal one ‘byte’. The high number of pixels in an image, along with other relevant information, thus results in a large amount of data packets – kilobytes and megabytes. Moving video is made up of a series of still images which is displayed in a quick sequence to create the illusion of a moving object. Standard formats use 24, 25 and 30 Frames per Second (FPS). The amount of data packets for one still image thus needs to be multiplied by the refresh rate (FPS), which will suggest the bandwidth required to transmit the video signal in the IP network for every second that it’s playing – for example in Mbps (Megabytes per second).

Once a signal is digital, the challenge is that the bandwidth required in HD video signals exceeds the capacity of most commonly used IP networks. These networks are adequate for basic networking requirements, but video streaming will consume the available data flow and congest the entire network, making it dormant for any of the users. Higher capacity networks are available, but at an inflated cost, which is difficult to justify for video streaming only, if not purposely required.

Video Compression
This brings us to the reason why certain video signals are being compressed for IP distribution. Many different compression formats are available and currently in use. These are divided into lossless and lossy codecs. Many video codecs are necessarily lossy, simply because of the idea of eliminating information to reduce bandwidth. Lossy codecs compress video based on many algorithms. Basic lossy codecs are throwing away data at regular intervals, which is effective to reduce bandwidth, but may result in a much lower image quality. Another effective lossy compression format is based on an analysis of the nature of human vision, which then dismisses excess information that the human eye would find visually redundant, such as close colour variances. Human vision is much more sensitive to brightness (luma) than colour (chroma) and would thus not distinguish between pixels of closely relevant colour. The third is called ‘chroma subsampling’, which reduces colour space information at regular intervals. Colour sample ratios are often seen as 4:2:2, 4:2:0, 4:1:1 and many similar ratios, which indicate the changes between the chroma samples from one row to the next.

Lossless codecs, as the name indicates, do not discard any information and thus compress video signals by preventing duplicate pixel information from being transmitted. Duplicate pixels exist where large areas in an image are made up of the same pixel information, such as a large background of the same colour with little motion, or adjacent video frames from long scenes in a movie or fixed film sets such as filmed interviews. These will result in many frames having similar pixel information. In these frames, only the changing pixels will be transmitted. Another format of video compression is to group average pixel values together, where several pixels are averaged out into one large rectangular pixel of the same value.

Most of these systems allow the user to adjust variable settings prior to compression, such as a specific resolution, frame rate reduction and bit rate to be preconfigured for maximum quality versus maximum compression. Multiple formats have been developed over the years. JPEG, HDV and MPEG-2 are examples of lossy compression, where the latter compresses data over multiple frames (interframe) instead of individual frames (intraframe). Mpeg4000 and its version 10 (H.264) are some of the most popular compression formats used in current systems.

Uncompressed video is also seeing the light of day, but in order to distribute uncompressed video one would need a network with the required capacity, such as 10Gbps and who knows what else the future holds. All that we know for now, is that the future of video distribution lies in IP systems.

Video over IP - the next wave.

Article published in ProSystems Africa News magazine Jan/Feb 2016 edition.

Access article on ProSystems Africa News Site

Traditional video distribution has come a long way since the days of analogue radio frequencies and higher resolution RGBHV signals.

The digital world brought us HD (High Definition) television, but with brand new technical challenges. HDMI (High Definition MultiMedia Interface) was introduced as a HD signal standard with a higher bandwidth requirement for more information transfer between source and sync (display) devices. Because of this, multi-media signals over copper cables are limited by distance. In addition, the HDMI equipment did not accommodate multiple source/multiple display architecture. Another challenge brought about by HDMI is HDCP (High-bandwidth Digital Content Protection). The latter is a control protocol embedded within the HDMI signal. Word on the street has it that Hollywood orchestrated this in an attempt to reduce the criminality around counterfeit copies sold on the black market, which costs content producers in dishonoured royalty obligations. HDCP ensures that both source and sync devices are conforming to a protocol – a digital handshake between licensed devices prohibiting the user from duplicating material.

HDMI soon became the norm in residential set-ups and later on in the professional audio-visual industry where many new technologies facilitated the distribution challenges. In professional video systems, one is more often than not faced with system architecture that requires video signals to reach greater distances than intended for HDMI’s design.Certain systems require video switching between multiple sources and others require multiple displays showing the same content. More advanced systems need a combination of both multiple source and multiple display devices with full routing flexibility. Many different technologies introduced solutions to some of these challenges. 

Balun (Balanced/Unbalanced) systems with transmit and receiver hardware on either side of a STP (shielded twisted pair) cable increased distribution distances but at an expense. More recently, HDMI optical fibre cables function in a similar style with transmit/receiver components integrated at both ends of optical fibre cables with power supplied by the HDMI ports. Fibre cables thus eliminate various components and instead provide a single point of failure with a neater installation appearance. The latest breakthrough in distribution technology is video distribution over IP (Internet Protocol). As more and more audio-visual systems integrate with IT systems, it was only a matter of time before IP networks were introduced to distribute HD multi-media signals. Technologies continue to develop with higher resolutions and current recording, distribution and display devices are capable of 4K UHD (Ultra-High Definition) signals with a resolution of 3840x2160 – four times that of Full HD(1920x1080). Video over IP has changed the architecture limitations of conventional video routing systems. 

Based on customer requirements, conventional systems select a frame to accommodate the configuration required before being populated with components. The negative side to this solution is that the frame size is established by either the number of inputs or outputs to be accommodated. This then results in the other side of the solution having to use the exact same frame even if only a fraction of the real estate is used. IP distribution systems utilise one multi-port switch with transmitters and receivers at both ends of the solution. Each transmitter will convert the HD signal to IP and send it to the IP switch. The receiving end will dictate an IP address where the required source is transmitted from and thus switched to the desired display. This design only requires an IP switch to accommodate the total number of connections (sources and displays) needed in a system. 

The greatest benefit of a video over IP system is that it utilises IT network infrastructure but in order to distribute uncompressed HD or UHD video, network infrastructure must be capable of 10Gb/s bandwidth. This might increase cost but will prepare networks for future IT requirements, assuming that the pace of development around the ‘internet of things’ remains the same. Certain video over IP systems will use video compression and thus require much lower bandwidth capabilities. This makes these systems more appealing because of an attractive bottom line. The question to ask is whether the objective of distributing true HD or UHD video is achieved. Another important factor to keep in mind is the HDCP protocol explained earlier. It might not be required when a local presentation is sent over a network as the content belongs to the presenter. However, the moment one decides to send a HD news broadcast or the latest release blockbuster over a network that is not HDCP enabled, the signal will be rejected by the display device, resulting in a ‘no show’. It is also of high importance to have the initial IT functionality still available on the IT network.

On a 10Gb/s system, each video endpoint is capable of delivering 1Gb/s allocation for internet only. Systems should also be capable of sending USB protocols over the same network and to make it more attractive to the AV professional. Control integration at each endpoint must be capable of delivering Infrared and RS232 protocols. Video over IP technologies are also readily available for the entertainment and staging industry where signal distribution has always been a challenge. System architecture is slightly different with a FOH (Front of House) sender unit – where source components connect – and a back stage distributor switch sending various commands and signals to relevant systems. Both components are linked by a single, two cable connection for redundancy. Some of the supported signals include audio and video as well as control protocols such as Dante and Artnet for lighting control – an important aspect of the live entertainment industry. Equipment is built for rugged on-the-road conditions and the architecture has revolutionised the requirements around live event set-up. In short: the future of video distribution lies with IP networking, with high enough bandwidth to accommodate all the components and technologies in today’s digital world.