UHD is firmly established worldwide as the new production and consumption format, which quadruplicates the number of pixels and improves the immersive experience of the viewer, with more than 15 million screens sold around the world. On the other hand, the new video coding standard, ITU H.265 (HEVC), has been found to be the most efficient solution for the distribution of UHD content.
For the third year in a row, SAPEC in collaboration with the Institute of Telecommunications and Multimedia Applications of the Polytechnic University of Valencia (iTEAM-UPV), have participated as the greatest exponents of the Spanish audiovisual technology, presenting a technological solution for the efficient use of the HEVC standard for the future distribution of UHD content with HFR.
The different international standardisation bodies, such as the DVB and the ATSC, are immersed in the definition of a new generation of UHD named “UHD-1 Phase 2”. The new features that will be introduced by this new format include the increase of the temporal resolution up to 100/120 fps, in order to increase the sharpness of high-complex sequences, such as sports and action content, improving the experience of the viewer. This feature is known as HFR (High Frame Rate).
HFR implies doubling the number of frames from 50 to 100 per second in the capture, which implies doubling the video bit rate from 12Gbps to 24Gbps in baseband. With this study, SAPEC has proven that the efficient use of HEVC only requires a 20% increase in the bit rate of the compressed signal. For example, if we have a UHD service at 50 fps coded with HEVC at 20Mbps, getting this same service at 100fps would imply coding it at 24Mbps to obtain the same image quality (see figure 3).
HFR backward compatibility
The introduction of new audiovisual formats must always take into account the high number of users that may not have replaced their devices, forcing the broadcasters to maintain two services: one with the old format and another with the new, which is called Simulcast.
Simulcast is completely inefficient from the bandwidth point of view, incurring in high costs for the distribution and broadcasting of content. In the face of this challenge, SAPEC and the iTEAM have looked for technological solutions alternative to Simulcast, which allow for providing UHD@HFR content to all users through a single service.
The proposed solution is based on the use of the temporal scalability capacities offered by ITU-H.265, which allows for the video coding at 100fps to be separated in two layers. One base layer compatible with the current UHD@50fps receivers and a “complementary” layer that allows for viewing the HFR content in a UHD@100fps receiver.
In front of a large number of industry experts, SAPEC and the iTEAM-UPV showed how this solution allows for reducing the bit rate by 40%, compared to the Simulcast alternative. (see fig2).
As a final conclusion, SAPEC and the iTEAM-UPV highlighted:
- Doubling the frame rate only implies a 20% increase of the bit rate.
- The HEVC scalability capacities allow for having an HFR service that can be viewed in non-HFR devices, reducing the bandwidth by 40% compared to simulcast.
- It optimises the content distribution costs, allowing the broadcasters to create backward-compatible HFR services.
SAPEC is currently one of the first companies worldwide to have professional real-time HEVC encoders.