Ultra-high definition (UHD) is and has been a hot topic in consumer appliances for years. Consumers want UHD and they want it in high-dynamic range (HDR). The UHD portion means simply more pixels and the HDR portion means the pixels are far more bright and colorful. For the consumer, this combination equates to incredibly beautiful television images and amazingly clear cell phone screens.
Combining UHD and HDR
However, UHD and HDR, when combined, represent a significant technical challenge for us in the display business. High pixel density in displays (PPI or pixels per inch) has outpaced a cable’s ability to carry uncompressed video data by a wide margin. Mobile screen resolutions since 2011 have doubled every year. HDR will add another 25% more data to represent each UHD pixel as each pixel needs 30 bits of data rather than 24 bits. On the other hand, the HDMI cable that connects the cable box (set-top box) with a TV, and the DisplayPort cable that connects a PC and its monitor, have grown in bandwidth by only 20% per year.
These industry specifications were developed by the HDMI Forum and by VESA (the Video Electronics Standards Association), respectively, with HDR in mind but the question remains, how does 2.2x more video fit in a pipe that’s only 20% bigger? The solution is to compress the pixels – very carefully.
The New DSC Standard
VESA recently introduced a revised Display Stream Compression (DSC) standard that does just that, visually compressing the pixel data in every video stream to a mobile panel, IT monitor or television. Samsung Display’s R&D Lab in San Jose works on video algorithms and we develop ways to tell if the end picture on a display is “lossless,” which means that even the most astute observer cannot tell whether a program was delivered with or without compression in the cable. Rather than use the well-known JPEG or AVC standards, which are perfectly good compression systems for natural images, photography or general TV content, the DSC must be invisible to the user. In other words, the display should look no different whether the cable carries compressed data or uncompressed data; the latter being typical for a full HD monitor.
What DSC 1.2 will Support
Last month, the VESA task group, which I chair, announced DSC v1.2. The new standard is designed for desktop monitors and televisions, supporting formats typically used in broadcast TV and Blu-ray discs. The new standard is future looking. It supports today’s content and future HDR content coding including 24-bit and 30-bits-per-pixel video, and higher color depth, too, up to 48-bit pixels. The fantastic range of colors available with HDR — 1 billion possible colors compared to standard TV’s 16 million colors — in better and brighter pixels, enables consumers to experience a “wow effect” when viewing a UHD + HDR program.
The Samsung Display Lab team has a deep understanding of compression algorithms, vision science and how imagery is seen. We gladly share our insights with VESA and other standards organizations. It is part of our commitment to making the world’s most desirable and technically proficient displays.
Now, tell us, do you think that UHD will make a significant difference in TV viewing, especially when combined with HDR?