Preface
SDI signal is a very successful interconnection technology in the radio and television industry. It has been widely used in digital video transmission. It really works well. It has served the industry for more than 30 years and has been developing continuously during this period.
According to the performance, a large number of SDI devices have been installed in production and distribution facilities around the world. These devices communicate with other devices through these 1-wire 1-signal coaxial SDI cables.
Establishment of basic rules
In the long developing radio and television industry, we have learned a universal truth: if a device has some vitality, radio and television engineers will not throw it away. The hardware equipment of SDI interface and SDI wire itself are still working.
Therefore, our view is that we are not facing a war between the old SDI guards and the new IP generation. On the slogans of many exhibitions, those sensational words, such as IP replacing SDI, will always attract people's attention, but this is not the case. Now is the time to correctly evaluate how SDI and IP adapt to our system planning.
Although we sometimes use the word "IP solution" for convenience, I actually mean the equipment and architecture that conform to the SMPTE ST 2110 standard (more broadly, the AIMS roadmap). We are optimistic about the future of ST 2110. The ST 2110 is the trend in the future, because it is a standard that is unanimously supported by the radio and television industry and has been verified by hundreds of high-profile projects, especially the rapid development of IP system in recent years.
Development and evolution of new media infrastructure
So, if SDI is effective, what drives the media infrastructure's demand for IP 2110? It is a technology that can endow higher capabilities: a new way and method to expand the boundaries of SDI in the past.
SDI works well within its limits. Up to HD (1080p) and 3G, it handles very well, with good cable transmission distance and a large number of optical fiber extenders. But with the arrival of 4K resolution, SDI also has some limitations. The 12G SDI is a great interconnection in the chassis or flight package, but for large facilities, this distance is not enough. In addition, the scalability of the 12G-SDI matrix system is limited for large facilities. With the development of content production and distribution towards UHD and HDR on a large scale, SDI must have flexible measures for our use. These measures are often problematic, and the signal quality and transmission distance will be limited.
The traditional SDI matrix has new limitations. If we design a system around the 288x288 SDI matrix, when someone urgently needs to schedule the 289th source signal, they will again face the problem of system workarounds and production restrictions. Then someone will need the 290th source signal... and so on. The matrix port scheduling in SDI facilities needs to be redesigned and allocated, and may conflict with other signals.
In addition, one of the popular advantages of SDI is that it embeds audio into it, so audio and video are kept together and synchronized, which is good in the media workflow where audio is closely embedded into video. But in the production field, audio is usually produced separately, and then recombined with video at the end of the production chain.
So in the production domain workflow, you have to extract the audio from the video, map them to the audio transmission line, and transmit them to the audio room, because mixing and all other audio processing occur there, and then return through the audio transmission line, and re embed the audio signal at each position of the video that needs to be switched with audio, which will result in a little out of sync audio and video. The complexity of embedding and de embedding, as well as the constant adjustment of video and audio delay, are daily realities in current program production.
It is obvious that the SDI video and embedded audio gradually cannot perfectly match the existing use requirements and system expansion. At present, many new radio and television stations have been built from scratch, and there are many new large-scale production and distribution systems. The operation scale and interconnection of SDI alone are extremely huge and unimaginable. Even for the typical new large broadcast system being built, the number of sources and destinations is amazing, and it needs to support signals such as UHD and HDR, which is far beyond the limit of SDI.
Multi platform distribution
Viewers hope to watch various video signals anytime and anywhere through cable, wireless TV or their mobile devices. This means that we need to output multiple specifications and release multiple versions; Such requirements In the traditional SDI workflow, the matrix ports will explode. IP based on SMPTE ST 2110 can now work effectively and is fully prepared for UHD, HDR and upward expansion. There is also the question of flexibility. In SDI, in order to reduce the number of matrix ports, devices are often built as "chains". But in an IP environment, everything is connected through a switch. Therefore, each interconnection point is essentially a routing point. Reorganizing to a new workflow is to choose a route.
This is true when you have the ST 2110 architecture. At this time, you are not constrained by a fixed number of intersections and a limited number of paths back to the matrix, but have a network topology that can reasonably grow, which is limited by bandwidth (not switching ports). The separated video, audio and data signals share a common switching structure, so that each device can only obtain the signals required for its work.
For the newly designed system architecture, the scale and scalability of the SMPTE ST 2110 architecture are obvious, but for economic reasons, even new construction projects will require some old equipment to be reused; For example, perhaps a new studio camera was bought only a few years ago, and how to integrate it into the new system architecture. A common method is to add ST 2110 conversion equipment when redeveloping the traditional architecture, and gradually move to the IP system. The hybrid architecture will be a good transition way.
Summary
Between SDI and IP, neither you nor I will die. We are sure that when we retire from this industry, there will still be a large number of traditional SDI devices in operation. But as TV engineers, we are not afraid of new developments; In fact, in the past many years, TV engineering has been constantly integrating new technologies and new developments.
At present, ST 2110 technology is being gradually supported from device suppliers, and it is verified by field cases - not scientific experiments.