Digital Foundry: Hands-on with PS4's PlayStation 2 emulation

UPDATE 21/11/15 11:38am: Just how much faster is the PS2 emulator compared to original hardware? We've just posted this extensive analysis using the three games we have available.

UPDATE 20/11/15 8:41am: Overnight, Sony has confirmed PlayStation 2 emulation for PS4, but is remaining tight-lipped on its plans for the project. "We are working on utilising PS2 emulation technology to bring PS2 games forward to the current generation," Sony told Wired. "We have nothing further to comment at this point in time."

Original story: It's been a long time since we first reported that classic PS1 and PS2 titles were heading to PlayStation 4, running under emulation. It's been so long in fact, that we began to wonder whether Sony had shelved the project. The company originally informed developers of the existence of the emulator at the same time it briefed them on the planned rollout for the PlayStation Now cloud service, way back in January 2014. Since then, the only hints at its existence came in the form of some telling PEGI game ratings, along with some sightings of PS2 classics appearing in shared media lists during the PS4 firmware 3.0 beta phase.

As it happens, the PlayStation 4's PS2 emulator is now available, released with no fanfare whatsoever. A new PS4 Star Wars bundle has been released, including a package of four 'classic' franchise titles: Super Star Wars, Star Wars: Jedi Starfighter, Star Wars: Racer Revenge and Star Wars: Bounty Hunter. All four titles are supplied via a single PSN code, as opposed to a physical disc included with the hardware. You'll note that three of those titles hail from the PlayStation 2 era, and after we downloaded them, it became clear that all of them are running under emulation.

How can we tell? First of all, a system prompt appears telling you that select and start buttons are mapped to the left and right sides of the Dual Shock 4's trackpad. Third party game developers cannot access the system OS in this manner. Secondly, just like the PS2 emulator on PlayStation 3, there's an emulation system in place for handling PS2 memory cards. Thirdly, the classic PlayStation 2 logo appears in all of its poorly upscaled glory when you boot each title. And finally, all in-game button prompts relate to the PS2's controller - nothing has been changed at all, effectively ruling out a remaster.

Upscaling? Probably not what you wanted to hear bearing in mind that older titles haven't aged well visually, and a disappointing result bearing in mind that our initial information said that Sony would be emulating these titles in high definition. Well, there's both good and bad news here. All 2D artwork in every title gets the upscaling treatment - there's nothing that can be done about that, and it can look pretty ropey. However, the 3D elements are substantially improved and do get a resolution increase.

Original PlayStation 2 titles ran at a range of pixel counts, but 512x448 and 640x448 were commonplace (God of War 2 even let you choose between the two). It's still early days in our analysis, but first impressions suggest that the emulator resolves a native resolution of 1292x896. Two black lines are added top and bottom to the image, before receiving a final upscale up to full 1080p. In effect, we're looking at around 4x the pixel count - possibly higher, depending on the title. Texture filtering also looks improved, but on close inspection we think that the increased quality is probably down to the extra resolution alone.

Overall impressions are positive - there's little that can be done to improve the quality of 2D assets, but the improvements to the 3D side of things are welcome. It looks like some kind of post-process effect is in place mimicking anti-aliasing - edges are surprisingly smooth, and there's little in the way of shimmer. Oh, and there's one more addition worthy of note: trophy support is added to the emulator - something we can confirm having unlocked one while playing Racer Revenge. On the face of it, this may seem to rule out emulation (trophies were never in the original games) - but this patent explains how it is done. Essentially, it seems the emulator tracks certain 'trigger' conditions required for specific trophies to activate - we expect that it is tracking the game state as you play.

Moving on, the outstanding question is one of performance. We've got some substantial improvements to image quality, but do the games run as they should - or dare we hope, better? It's early days right now. In truth it's been a while since we analysed PS2 titles, and getting a clean 480p feed isn't easy - even with backward compatible PS3s in the house. However, it's certainly looking promising. The emulator is clearly running these games more smoothly, with Jedi Starfighter hitting 60fps while the game running on PS2 hardware has nothing like that level of output.

We've not run the numbers yet, but just looking at Racer Revenge side-by-side sees another substantial increase to game fluidity. Obviously, these aren't the most testing of games and other titles may perform entirely differently - but imagine Metal Gear Solid 3 with higher frame-rates, the God of War titles running at a locked frame-rate, or Gran Turismo 4 operating without any tearing. We're really looking forward to seeing what this emulator is capable of.

The arrival of PS2 emulation on the PlayStation 4 is a big deal - we reached out to Sony and await comment, but it is a little odd that a lovely piece of technology that's bound to excite a lot of interest has slipped out without any kind of fanfare. The PlayStation 2 is one of the classic pieces of console hardware, and the ability to access that back catalogue with enhanced visuals is a tantalising proposition. And with that in mind, it's actually a bit of a shame that the emulator has launched with a trio of mediocre titles, as opposed to a sparkling line-up of the console's greatest hits.

On top of that, we can't help but wonder whether the launch of Microsoft's Xbox One backward compatibility has had any kind of bearing on Sony's internal strategy. The Redmond giant is allowing gamers to use their existing discs to play Xbox 360 games on its latest console (albeit as a 'key' that prompts a full download). Meanwhile, the evidence to date - not least the ESRB ratings for PS2 classics - perhaps suggests that Sony's plans for the PS2 emulator involve selling these titles digitally, just as it did last-gen. With the PS2 emulation now in the hands of consumers, hopefully Sony's plans for the technology will be revealed shortly.

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