Will high-capacity Blu-Ray mean better graphics than Killzone 2?

Will high-capacity Blu-Ray mean better graphics than Killzone 2?

It was recently announced that Blu-Ray discs were going to be able to increase capacity and that the PS3 would be able to read these new high-capacity discs. It got me wondering what this could mean for PS3 games. To understand what the 400Gb, or even 1Tb, Blu-Ray discs mean to gaming and specifically the PS3, you need to look at some technical and business aspects, which have been roundly ignored, or perhaps not even considered, by a lot of “pundits”. I’ve tried to look at some of these and in some cases simplified interesting points to try and make them understandable. I’m not going to compare the Blu-Ray capacity to the Xbox 360 DVD capacity, so I’ll leave it to others to interpret what I discuss as to what it means for conquest over Microsoft. What I am interested in working out is whether increased storage capacity for the PS3, above the current 50Gbs, can mean bigger or better games.

There are two ways you can see a 400Gb disc being used by developers. The first is to make games bigger and longer. Keep the data per minute of gameplay consistent with today’s rates, but simply give us all more. Unless game prices can rise to match the increased development cost, while at the same time not damaging the elasticity curve that governs purchasing (how many copies of a game will be sold decreases as price increases), it’s hard to see why developers would do this. It doesn’t take a degree in economics to see why not. Better sense to release the game and then sell expansions either online or as expansion discs.

The other possibility is that instead of using compressed textures and the like, developers have the luxury of using the uncompressed, highest quality textures giving the graphics an never-before seen quality (that’s the theory people seem to be operating on). But there are problems with this also…

The amount of data a disc can hold is not much use if the access speed of the drive doesn’t allow for the data to be shifted from the disc to the machine’s memory fast enough. The PS3 has a sustained access speed of 72Mbps according to its specification. (That’s Megabits, not Megabytes.) This works out as 9 Megabytes per second, sustained. Now anyone with working knowledge of computers, especially from the early CD-ROM days, will know that getting a sustained rate of transfer needs several things. The disc has to spin up, find the place on the disc where the data requested starts (what is called seek time) and, assuming the data has been optimised so that it all exists in one long string from start to finish on the disc, not split into several fragments, read it into memory via the CPU. It then has to get the next bit of data that the machine needs, which is unlikely to be sequentially placed on the disc. (Think of it like this: you may be loading some character information from the start of the disc, and then some environment data for level 1 and they might be placed right next to each other on the disc, so the seek time is low when loading level 1. When you’re on level 10 though, the same character information might be needed from the start of the disc, but the level data is at the end, so the seek time increases.)

The point of all this is that sustained access speed, and real world access times that the PS3 can achieve from a game developer’s point of view will be wildly different. So, it’s unlikely that it makes much sense to include uncompressed textures as it would take too long to load them. It’s likely, given the speed of the PS3 CPU vs the speed of the 2x Blu-Ray access in the PS3, that technically it would make more sense to have a smaller file compressed on the disc for fast access, then very quickly uncompressed by the CPU. You also have to remember that compression doesn’t always mean lossy compression. It’s perfectly possible to compress data without losing any data (Zip compression is one good example of lossless compression (implemented in the TIFF image format, for example), while JPEG is a lossy compression [some data is thrown out when the image is saved and “guessed” when re-loaded]).

Additionally, all this quality information would need to be stored somewhere once loaded from the disc in order to be used, most usefully in RAM (though it could be swapped in and out from the hard drive). There isn’t enough RAM to do this, quite simply because there’s never enough – the more RAM you get, the more developers will use up. So RAM will limit the amount of concurrent data a game can use from the disc, irrespective of the disc’s capacity.

What’s most likely from a technical point of view is that if developers are filling up the current 50Gb discs (which is rare, so far) they may opt for a bigger disc and relax some of the compression, so textures and the like can be marginally improved. (Clearly, you are going to need a big, very high quality, HD TV to benefit – if anyone (anyone?) is running a PS3 on a CRT, you’re not going to see any difference.) It’s hard to see this requiring an 8-fold increase in capacity though.

The other aspect that comes into play is cost of production. Assuming Blu-Ray duplication costs mirror the way DVD dual-layer duplication costs went, then single and dual-layer duplication costs will drop (increasing margin to publishers) while multi-layer (400Gb is 16 layer) discs will cost significantly more (decreasing margin to publishers). One area where multi-layer sounds tempting is to TV aficionados – we could get the whole series of something on one disc and watch it all without needing to swap discs. Unfortunately, business comes into play here with what is called “Perceived Value for Money”. (Note, not real value for money). This is why you get DVD Special Editions with 2 DVDs in it, rather than the cheaper to produce dual-sided DVD. The same data can be included on both, but the customer perceives more value by getting 2 discs. Frankly, I find it hard to believe that perceived value for money would remain consistent for customers seeing a single DVD style case with one disc in, as for a DVD boxset with six discs. And I suspect business managers will agree. Put simply – you can’t charge £60 for a single disc (and one that to the average punter looks just like a DVD) and sell as many.

What all this means is that the 400Gb or 1Tb limits on Blu-Ray are a fantastic technical achievement, and as a geek, I doff my cap to the boffins who managed it. But, it’s hard to see what it can be used for, except that history shows that up until now we have always found uses for extra capacity.