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In Theory: How The Cloud Could Run Backwards-Compatible PlayStation Games

Are older titles a better match for current limitations in cloud tech? Digital Foundry investigates.

The Sony/cloud collaboration story just keeps on rolling, this time with the revelation that older PlayStation titles will be streamed to PS3 and PlayStation Vita. ran the story first with editor Matt Martin having spent a while chasing down multiple sources willing to confirm it.

It's an intriguing solution to a difficult challenge. Back-compat is seen as a bit of a cash cow: money for old rope, if you will. Both PS3 and PlayStation Vita are more than capable of running PS1 and PSP titles under full software emulation, but downloads that are anything up to 1.4GB in size with no prospect of playable demos erects a barrier to entry that probably makes actual sales of these titles very low. In this sense, the cloud offers plenty of advantages: instant access to the whole library of games on both systems, plus playable demos by default, because the system would simply time-limit access.

PS1 and PSP emulation is a walk in the park, really - it's PlayStation 2 that is the real challenge here. Having removed back-compat hardware from the PS3 early on in the machine's lifetime, Sony has struggled to convincingly simulate the challenging graphics synthesizer chip via software, and only a small handful of emulated PS2 games are available to download from the PlayStation Store. Cloud could make the process a lot easier and significantly more accessible.

Firstly we should assume that Sony would be utilising the existing hardware in the datacentres of its partners - which would be PC-based in nature - because rolling out bespoke hardware would be far more expensive. This would represent zero hardware investment by Sony and its existing PS1/PSP emulators could be easily re-factored into PC compatible software. Bearing in mind that the open-source PCSX2 emulator (built from the ground up with no inside access into the original hardware) makes a good fist of running virtually any PS2 title, we can only imagine that Sony's own code would be better still.

Other aspects of this concept also make a good amount of sense - not least that PS2-emulated titles would also work on Vita, which simply doesn't have the horsepower to emulate last-gen titles without complete ports being undertaken.

"We're still sceptical but implemented well it could convincingly re-energise a vast and impressive back catalogue of quality games and could prove to be a serious boost to the PlayStation Network."

Our comparison of Shadow of the Colossus running on PS2 and in HD on PS3. Owing to the more simplistic nature of the visuals, excellent picture quality can be attained at low bit-rates making last-gen titles a pretty good match for the limitations in cloud video encoding. This video is running at 1280x720 resolution and includes a fair amount of HD source material but rarely troubles the 2mbps barrier.

A last-gen approach to the cloud also helps mitigate the image quality issues. Game video is really difficult to encode effectively on a cloud system, but the job becomes a whole lot easier if we're addressing older, visually less complex games. With a couple of exceptions, resolution on PS2 titles tops out at a mere 640x448 - meaning no HD streaming is required. Detail levels are also much lower generally, meaning that the bandwidth requirement would drop still further. Getting the balance right between bandwidth and quality would be a lot easier and based on our own tests encoding PS2 titles for our HD remaster comparisons, 1.5mbps to 2mbps would be more than enough for a majority of games.

We can foresee pitfalls, however. First of all, encoded picture quality would need to be very good. Upscaling a poorly encoded 480p image to 720p (or 1080p, depending on the user's set-up) would only serve to emphasise inadequacies in the video - similar to how low bit-rate digital TV channels can look absolutely awful viewed on an HDTV.

Secondly, there's a real danger that latency would be a deal-breaker, to committed gamers at least, because one way or another we're going to be looking at games that simply don't play as well as they did on the original hardware. The basic principle of Cloud gaming is that PC versions run the game simulation at 60FPS rather than 30FPS, input latency is reduced and that saving is used to mitigate encoding/decoding and transmission lag.

Any kind of legacy console emulator for cloud systems would need to be built to get player commands processed as quickly as possible - faster than they were on the original hardware. Even factoring that in, plus the general improvements we have seen in cloud latencies, the fact remains that a lot of the original PS2 games ran at 60Hz already so the experience is almost certainly going to be diminished regardless in those cases. The question is to what extent the lag would manifest and whether the majority of the userbase would notice.

We still view this story with some scepticism, but implemented well it could convincingly re-energise a vast and impressive back catalogue of quality games and could prove to be a serious boost to the PlayStation Network. Convenience and accessibility to a mammoth library of legacy PlayStation titles is an irresistible possibility for Sony and third-party publishers - not to mention gamers - and the notion of being able to stream with no problem to any device capable of decoding h.264 video is also a winner. It wouldn't just be PS3 and Vita invited to the party, either, because Bravia HDTVs and PlayStation-certified mobile devices are viable targets too...

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