YouTube Supports 4K2K, Quad HD

4K2K. Quad HD. Whatever these terms refer to, YouTube is supporting them via an “Original” option in the video settings (source: The Official YouTube Blog). Let’s try to figure out what these terms mean. I will be using the term “pixel format” to refer to things like 1920×1080; resolution is not the right word as it refers to pixel density and shown as pixels per inch (PPI).

4K2K refers to a pixel format of around 4000×2000. Pixel formats and aspect ratios differ for digital film standards (source: Wikipedia):

  • Full Aperture 4K: 4096×3112, 1.32:1
  • Academy 4K: 3656×2664, 1.37:1
  • Digital Cinema 4K: 4096×1714, 2:39:1 or 3996×2160, 1.85:1

According to the Digital Cinema Initiatives (DCI), a joint venture among Disney, Fox, Paramount, Sony Pictures Element, Universal, and Warner Bros. Studios, 4K2K refers to motion picture with a pixel format of 4096×2160 (source: DCI Digital Cinema System Specification Version 1.2, in PDF).

It can also refer to a simple doubling of 1920×1080 pixels in the horizontal and vertical directions to 3840×2160, resulting in the quadrupling of the total number of pixels from 2,073,600 to 8,294,400. And hence the term Quad HD. A more technically correct term would be Quad Full HD since you can fit four 1920×1080 screens. Full HD is yet another industry jargon for 1920×1080 and usually associated with progressive scanning at 60 fps.

YouTube has conveniently listed all 4K2K titles for anyone with the bandwidth and just as importantly a 4K2K-capable display for the complete experience. On the list these are the titles that allow you to view the video in the Original pixel format, as of this writing: Life in the Garden, Surf NYC, 2nd Movement for Violin, and Lupe. Secret World seems to be limited to just 1080p.

I watched these 4K2K titles on a 1920×1080 LCD and was fairly impressed except that there were too many artifacts related to compression/decompression. On the other hand, I captured the screen (above, cropped to 512 pixels wide) and the quality of the image was outstanding. For quite some time most of us will be relegated to enjoying 4K2K videos on less-than 4K2K displays. Display and capture devices capable of 4K2K are incredibly rare and expensive. For example, JVC’s DLA-RS4000U reference series 4K2K home cinema projector has a MSRP of US$175,000.

What’s next?

Ultra High Definition (UHD) is the next step after High Definition (HD) and 4K2K/Quad HD. But before we get into UHD we have to understand where we are with HD. The ATSC standard was developed by the Advanced Television System Committee for digital TV transmissions with a maximum pixel format of 1920×1080. ATSC replaced the analog NTSC TV system on June 12, 2009 in the US. The maximum pixel format of 1920×1080 runs at a maximum frame rate of 60i where the letter ‘i’ is interlaced and the 60 refers to frames per second. This can also be shown as 1080/60i. According to the ATSC standard progressive scanning for the highest pixel format  include 1080/30p and 1080/24p. Progressive scanning at 60 frames per second is not terrestrially broadcasted but can be created with the deinterlacing process in the TV or an external box. Non-broadcast material such as Blu-ray has 1080/60p. So that’s HD; what is UHD?

The NHK (Nippon Hōsō Kyōkai, official English name: Japan Broadcasting Corporation) Science & Technical Research Laboratories developed UHD, which is also referred to as Super Hi-vision. The pixel format jumps to an amazing 7680×4320 and the frame rate to 60p. The short form would be 4320/60p. (All HDTV and UHDTV feature a 16:9 aspect ratio.) Super Hi-vision was demonstrated at World Exposition 2005 in Aichi, Japan on a 600-inch display. On November 2, 2005 NHK successfully transmitted Super Hi-vision signals between Kamogawa (Chiba prefecture) and its Science & Technical Research Laboratories). The distance between the two locations is 260km and is connected via optical cables. Super Hi-vision video and audio were uncompressed and transmitted using Dense Wavelength Division Multiplexing (DWDM). You can find more information at NHK.