Television set manufacturers need to keep their factories operating by creating a market for higher quality display. The next generation TV sets will present 4K images at higher frame rates with improved contrast ratios and larger colour spaces. Those are factors the manufacturers hope to be able to sell to a world-wide audience.

Likewise, content owners hope to charge a premium for brighter and sharper productions. Consumers want bigger displays and larger screens look their best with this new content. So this transition will happen, but getting there will be challenging. Let’s consider what advances need to be surmounted to make UHDTV as ubiquitous as HDTV is today.

Defining the data delta to existing systems and methods

The following chart shows the additional data required for more pixels, better pixels and faster pixels as compared to HDTV 720P/60 and 1080/29.95 using the same codecs.

1. 12 bit recording but only 20% increase for consumption with helper signal

2.  Progressive is easier to encode than interlace

3.  Increased resolution increases encoder efficiency

As can be seen, without a better codec, we would need to increase both storage and bandwidth throughout the whole production chain by 3.5 times, with the resulting cost increase. 

École Polytechnique Fédérale de Lausanne (EPFL) did a study to evaluate the subjective video quality of HEVC (High Efficiency Video Codec) at resolutions higher than HDTV. The study was done with three videos having resolutions of 3840×1744 at 24 fps, 3840×2048 at 30 fps, and 3840×2160 at 30 fps. The five second video sequences showed people on a street, traffic, and a scene from the open source computer animated movie Sintel.

The video sequences were encoded at five different bitrates using the HM-6.1.1 HEVC encoder and the JM-18.3 H.264/MPEG-4 AVC encoder. The subjective bit rate reductions were determined based on subjective assessment using mean opinion score values.

The study compared HEVC MP with H.264/MPEG-4 AVC HP and showed that, for HEVC MP, the average bitrate reduction based on PSNR was 44.4%, while the average bitrate reduction based on subjective video quality was 66.5%.

Applying the PSNR based reduction to the results shown in the contribution chain chart gives about 100mb/s, still twice what we have today but less than the x 3.5 previously predicted.

Now let’s consider the viewing aspects. Given that a HDTV (1080P/50) signal compressed to 10Mbs is degraded perceptibly but not annoyingly using AVC, then the equivalent quality for UHD would require 26 Mbs (66% improvement) using HEVC because 4 times the data needs to be transmitted. Adding the 20% required for HDR backward compatibility results in approximately 30 Mbs being required.

The pipes are too small

This is the tail that wags the dog. Unless we can provide the consumer with 30 Mbs they are not getting what they paid for. The chart below shows some of the delivery methods available today.

1.  German TV Satellite Broadcast

2.  ATSC Futurecast tests late 2015 (HDR possible but not used)

3.  Maximum Video Bit rate

4.  Netflix only does Movies. HFR (48p) announced but not delivered

The currently available bit rate for ATSC 3.0 using 256 QAM is 26Mbs which would result in a clean 4K transmission but all current tests use less. At this point there are three ways to deliver a signal to the home that approaches the capability of the display device. You can download a file for playback from your hard drive, use a Blu-ray player or a satellite dish.

Fortunately for broadcasters experience with HD has shown that the average consumer is willing to accept reduced quality in exchange for more program choices.

The next article will look at the challenges resulting from higher quality displays that will ripple back into the production pipeline to support live TV.