UPDATE 14/2/17 4:20pm: The results are in for GTA4's Episodes from Liberty City, tested via Xbox One backward compatibility - and perhaps not surprisingly, we're seeing the same kind of performance profile we saw on the main game.
As expected, the look of all the titles is identical to Xbox 360 in terms of image quality, but again there are issues in performance. Frame-rate is higher, but as the game runs unlocked, variance in frame-pacing produces noticeable judder that is far less of an issue when running the same titles on original hardware.
Curiously though, the Ballad of Gay Tony appears to have fewer issues in this regard, with a turn-out that is closer to the Xbox 360's presentation. However, it's still not right and we remain hopeful that the Microsoft back-compat team revisit these titles with a view to stabilising frame delivery.
Original story: There are now well over 300 titles running under Xbox One backward compatibility, but arguably, this trio of releases are some of the most important. Grand Theft Auto 4 was a huge title in its day, its popularity only bolstered with the release of its standalone episodes - The Lost and the Damned and The Ballad of Gay Tony. All are now available to play on Xbox One, but is the experience as good - or better - than it was on original Xbox 360 hardware?
We're currently in the process of testing all three releases, but we wanted to get some results to you as quickly as we could, so we concentrated efforts on the original GTA4 - and the results are fascinating. There's no doubt that frame-rates are improved over original hardware, and in many other back-compat titles, that's a very good thing. Red Dead Redemption and Undead Nightmare offer up a tangibly improved experience on Xbox One, after all. GTA4, however? We're not so sure.
The key difference here is that the original game operates with an unlocked frame-rate, running above and indeed below the console-standard 30fps. New frames are delivered somewhat unevenly as a result, usually at 16ms and 33ms periods when the game is running well. On paper, Xbox One looks good. It hits the same performance level as original hardware, but can actually deliver anything up to a 5fps advantage. In terms of the quality of Microsoft's virtual machine, this is impressive - GTA4 hits CPU hard, in particular.
However, frame-pacing on Xbox One isn't quite right. Where 360 delivers new frames in 16ms and 33ms intervals, Xbox One often tosses in a bunch of 50ms and even 66ms spikes. The end result is that while mathematically, GTA4 runs faster on Xbox One than it does on Xbox 360, the experience is something else entirely. It feels choppier and more uneven, while controller latency - hardly one of the game's strongest points on original hardware - sometimes feels significantly laggier on Xbox One. In certain areas, frame-pacing seems to normalise but by and large, in-game performance seems less stable.
Microsoft's Xbox One backward compatibility team has been hitting it out of the park recently - we've reached the point where the virtual machine is capable of significantly improved GPU performance, and even CPU throughput seems to outpace the original Xenon tri-core PowerPC processor. And as we saw in Red Dead Redemption - running on very similar engine technology - games can run more smoothly as a result, much closer to their target frame-rates with fewer dips in performance. However, the evidence suggests that GTA4's unlocked frame-rate is causing issues here and in motion, the experience doesn't look or feel quite right.
Given a 30fps cap - something we saw in both Red Dead Redemption and indeed GTA5 - we can't help but feel that Xbox One back-compat for this game would run significantly more smoothly, even if this would see a reduction in frame-rate throughput. As things stand, GTA4 is one of a small number of back-compat titles that we'd prefer to play on Xbox 360 instead, and we hope that the back-compat team goes back to take a closer look at the frame-pacing issues here. Whether this extends to The Lost and the Damned and The Ballad of Gay Tony remains to be seen - but we'll be reporting back soon with the results of our testing.