With the TV market slowly but gradually shifting from 4K to 8K, some are suggesting Ultra HD Blu-ray discs and players should follow suit. That’s not likely to happen, for a couple of reasons.
First of all, almost nobody has 8K TVs yet. IHS Markit pegs the household penetration for 2020 at well below 1%. Even in Japan, where the Tokyo Olympics will be shot and broadcast in 8K, the penetration will be just 0.1%. It’ll be a few years before there is a decent installed base of them.
Of course, you may say this situation is not unlike that of 4K about 6 years earlier, and yet we got the 4K Ultra HD Blu-ray disc format, but some circumstances are different. More about that in a minute.
Secondly, there is no 8K movie or TV content, and there isn’t going to be any any time soon. There is barely even any real 4K content and Hollywood is not in much of a rush to start producing it. Most movies are still finished at 2K. Even movies that are shot at higher resolutions (2.8K, 3.4K, 4K, 6K, 8K) typically get a 2K DI (Digital Intermediate – the main deliverable of the Post Production process, from which all theatrical and home video distribution media are derived) as CGI (computer-generated imagery i.e. graphics, also referred to as VFX or visual effects) are typically rendered in 2K (a resolution comparable to 1080p HD), because of a combination of time constraints and cost savings. Gradually, movies finished in 4K are becoming less exceptional but they’re not the norm yet and at the time of writing no Hollywood movie has been done in 8K yet.
That means the only sources of 8K content in the short term are going to be powerful gaming PCs, next-gen games consoles (PS5 and the next Xbox) and consumer cameras, including high-end smartphones.
The outlook for optical discs
By the time these two things change, it’s probably too late for an 8K disc format. No company is going to invest in a next-gen optical disc format and associated player hardware. The product category is in decline since years. 4K Ultra HD Blu-ray is not going to become a mass-market product but remain niche. We are lucky that we got the format in the first place. It’s not going to return optical discs to a growth market and 8K even less so.
Two major brands in the video disc player market, Samsung and Oppo, have exited the business last year, and LG hasn’t renewed its modest line-up of players since CES 2018. There have been no new entrants after Pioneer. Note also how no low-cost Chinese brands have entered the market like they did with DVD and to a lesser extent with BD players. There’s not a whole lot of competition.
Brands we’re left to choose from are Panasonic, Sony, Pioneer, LG, Funai/Phlips/Magnavox in the USA (although Funai hasn’t introduced the prototype it presented earlier, and the Philips/Magnavox products haven’t been renewed after their second iteration), and of course Microsoft’s Xbox One S/X, which brings us to games consoles and the announcement by Sony that PlayStation 5 will use 100GB BD-ROM discs for games and the optical drive will function as a 4K Ultra HD Blu-ray player – a welcome boost to the 4K disc format's longevity for movie publishers and consumers alike.
There seems to have been a 10-year cycle in video disc formats, with DVD-Video introduced in 1996, Blu-ray Disc in 2006 and Ultra HD Blu-ray in 2016 (see A brief history of Ultra HD Blu-ray). An obvious date after that would be 2026 but it’s hard to tell what state the optical disc market will be in by then except probably not great.
What if they used the current disc?
If 8K on disc is going to happen, it’s probably going to be on the current BD-ROM 3.x disc format. It can be done, but the challenge is going to be whether the 100 GB disc capacity will allow enough playing time without sacrificing picture quality, which would defy the whole point of 8K.
Some key numbers: A triple-layer UHD BD disc has 100 GB capacity, with a maximum transfer rate of 128 Mbps. 8K video requires 4 times the bandwidth of 4K video as there’s no economy of scale when scaling spatial resolution. For documentaries and other non-cinematic content, a doubling of the frame rate is desired in order to combat motion blur which becomes more noticeable with increased spatial resolution. Fortunately, this improves encoding efficiency, as differences between successive frames become smaller. Reportedly this will increase the bandwidth with only 15-25%.
For theatrical content however, we may assume a 24 fps frame rate is maintained. With the current state of the art codec HEVC, streaming services like Netflix recommend a 25 Mbps bandwidth pipe to sustain a 4K stream of 15 Mbps on average. This is substantially lower than 4K Ultra HD Blu-ray, which easily uses 50-70 Mbps on average with even higher peaks.
A quick back-of-the-envelope calculation tells us that a 100 GB disc, if used at 100 Mbps, can hold 136 minutes of video. Coincidentally (or perhaps not) this is very close to the 135 minutes that was always quoted as the ‘running time’ of the DVD format. I suspect that this duration covers 95% of all Hollywood movies, which seems to be backed up by this chart (source: Stephen Follows).
Now the question is: Would 100 Mbps give sufficient picture quality to do justice to 8K video, for movies at 24 fps and documentaries at higher frame rates? If you’d ask Netflix the answer would surely be ‘yes’. If you ask the companies currently releasing 4K Ultra HD Blu-ray discs, it will be open for debate.
Relief may come from raising the maximum transfer rate, as this would not impact the disc spec much but merely what disc players have to be capable of processing – bearing in mind, of course, that raising the bit rate will shorten the play time.
Further relief may come in the form of new codecs. The successor the current HEVC (High-Efficiency Video Coding or H.265) standard is one called VVC (Versatile Video Coding or H.266). It is currently in draft and planned to be completed by July 2020. The new algorithms should have 30-50% better compression rate for the same perceptual quality, likely making publishing of 8K movies in good quality possible on 100 GB discs.
The official 8K Association recently felt compelled (no doubt after getting asked by numerous journalists) to issue a statement that an 8K Blu-ray format should not be counted on.
While this seems a fair statement, considering what the first part of this article discussed, please keep in mind that the 8K Association is (yet another) organization led by Samsung, a company that has exited the optical disc market altogether. Perhaps it would be better to ask the BDA (Blu-ray Disc Association) where Sony and Panasonic play a major role.
We’re probably not going to see a new optical disc format with higher capacity, using shorter wavelength lasers (never mind the fact that ‘UltraViolet’ discs would be terribly confusing), but 8K video could probably be squeezed onto the current 100GB BD-ROM 3.0 discs with decent quality when using new codecs like VVC. While such standardization would involve much less effort than previous video disc formats, it’s unlikely to happen for now considering a complete lack of 8K content and an installed base of 8K TVs that will take years to grow.
Yoeri Geutskens has worked in consumer electronics and telecommunications for two decades. He works as a consultant in media technology and writes about high-resolution audio and video. You can find his blogs about Ultra HD at @UHD4k and @UltraHDBluray.