Madrid, Mexico City, Copenhague – 4 Diciembre de 2020
SAPEC cooperates with RTVE to successfully demonstrate that 8K transmission over DVB-T2 is possible
With SAPEC´s support on encoding & compression, the UPM-RTVE chair carries on the world first UHD 8K broadcast transmission over a DTT channel.
This pilot test was conducted last October from different transmission points including Torrespaña or the UPM College Telecommunication. The presentation and demonstration of this event was streamed1 from the RTVE Institute (Madrid) within the framework of the RTVE-UPM Chair. This test has been dubbed by many means as a global milestone in the Broadcast sector, being the world’s first broadcast of an 8K signal over a DVB-T2 channel.
8K is a new video format with a resolution of approximately 33 million pixels per image. Within the standards of the digital television industry, it is more specifically associated with a resolution of 7680 pixels and 4320 lines. It is therefore a format that doubles the number of pixels and the number of lines relative to 4K, which has 3840 pixels and 2160 lines. This means that it quadruples the total number of pixels: 33.177.600 compared to 8.294.400 pixels of the 4K.
The best technique currently available for compressing 8K video is the HEVC standard (ITU H.265). As already mentioned, the 8K format quadruples the number of pixels relative to 4K, which implies an increase in the bandwidth requirement needed to transmit the signal.
Miguel Cristobal, CEO at SAPEC, exposed during the semi-presidential event the different challenges that SAPEC has faced on this pilot: “The challenge for SAPEC engineers has been to compress the UHD 8K signal that represents more than 48Gbps of video, at less than 33 Mbps2, maintaining the video quality that this type of signal requires. This means generating a compression ratio from 1000 to 1. This challenge has been made possible by the ability of SAPEC engineers to adjust all parameters and optimize the tools enabled by the HEVC encoding standard, to reduce bitrate.”
In addition to bandwidth requirements, SAPEC also had to meet the required time and process capacity requirements. For example, for progressive video at 50 images per second, means an average compression time of 20 milliseconds or less. Compared to 4K we would be talking about compressing 4 times more pixels in this short period of time, which with current technology is still challenging. To address this problem, the solution is to increase the computing capacity of the hardware, and to use different techniques to obtain those results.
“The size of the content was of a significant magnitude due to the high resolution, and it has been a challenge to handle it. The hardware available on the market has been pushed to the limit and spatial and temporal paralysis techniques have been used to make content management possible,” Miguel Cristobal continued.
The evolution to 8K has several perceptual advantages that go beyond an increase in image detail. Although today there are already products on the market that support 8K, there are still elements of the transmission chain in which there is still considerable job ahead.
The problems that arise for compression, in terms of bandwidth and increased processing capacity (although they could be covered with current tools), it is to be expected that can be solved with the emergence of new compression standards and the improvement of current hardware. At the same time, standardization organizations still have tasks in the pipeline as for example, publishing standards that ensure proper interoperability of all equipment, both at the physical interface level and at the stream signaling level.The companies that, together with RTVE-UPM, have made success possible are Cellnex Telecom, Dolby, SGO, Sony, Televes Corporación (Gsertel, TRedess and Televés) and SAPEC.
SAPEC, which has always defined a company with R&D DNA, adds another milestone to its career as a company in the field of research and development in the Broadcast sector. SAPEC has participated over the past decade in high-caliber technological projects such as EUREKA projects where it has worked on defining the UHDTV Workflow in DVB or developing the first encoder with DVB-3D implemented (3D-JEDI). In addition, SAPEC has collaborated on UHDTV broadcasts on DVB-S2 or DVB-T2 in different editions of Mobile World Congress. Finally, it should be mentioned that SAPEC has been a collaborator and invited to participate in different editions of the SMPTE conferences being the last topic also related to UHD: “HEVC Mezzanine Compression for UHD transport over SDI&IP infrastructures”.
With this new research project, SAPEC not only puts the pin to a decade of important research projects for the Broadcast but puts the first stone into 8K UHD signals compression.