Possible cause of random stuttering? 60 fps vs 59.94 Hz | Forums

[rlmergeuser]

(Cross-posted from the Steam forums.)

What follows is semi-informed, semi-baseless speculation, so please bear with me...

This is about the issue where the game runs perfectly one second, and then starts stuttering badly the next, for seemingly no reason. The cause of it is v-sync, I'm absolutely certain of that. With v-sync enabled I invariably get the stuttering every now and then, lasting a good while every time. With v-sync disabled it never happens. I get some screen tearing instead, but the stuttering is completely gone. It doesn't matter if I activate v-sync from within the game or from the Nvidia Control Panel, it happens either way. The question is why v-sync makes this happen.

What's interesting is that MSI Afterburner reports exactly the same framerate at all times, no matter if v-sync is enabled or not and no matter if the game is currently visibly stuttering or not: 59.9 to 60 fps. It keeps flipping between these values, which unless I'm mistaken is because TVs (and also most/some monitors) actually refresh at 59.94 Hz, not 60 Hz. The framerate never changes from this, not once, and all through this my GPU utilization is at about 65%, so it isn't exactly being pushed to its limits. Therefore I feel pretty safe saying that the issue lies not with my hardware, but with the game engine and how it handles updates. Again, my framerate never changes, it's rock solid (note: the framerate does drop a bit if I enable the advanced visual settings such as high quality shadows, so Afterburner is definitely reporting it correctly).

Now, what does the Trials Evo game engine run at? 60 hz, according to the people at RedLynx (also evident by the fact that even without v-sync the framerate will never go above 60 fps). Is it possible that there's some conflict here, with the game being hard-coded to update at 60 Hz but the GPU wanting to update at 59.94 Hz (since it's v-syncing with the TV), causing the game and graphics updates to drift out of sync, eventually introducing the stuttering in the engine? I may be way off base here, but it sounds sort of reasonable to me. And I wouldn't be surprised if the people who claim to never have experienced any stuttering in this game are playing it on a 60 Hz monitor. This wouldn't happen to them if what I'm suggesting is true.

After a while the game always stops stuttering, and it usually does this instantly if you just restart the level. Not only that, but just pausing to bring up the menu for a few seconds usually fixes it for me. Doing these things seems to make the game engine's updates "re-align" with the graphics updates, and the game will be perfectly smooth again for a while.

Maybe there is something to this, maybe it has nothing to do with it at all. And even if it's exactly what's going on, only RedLynx knows if it can be fixed or not. But what's completely clear, at least in my case, is that v-sync is very much causing some weird stuff to happen to this game's engine.

[WakeXT]

Can't comment on the TV's lower Hz and if that causes a problem, not enough theoretical expertise nor the hardware to test available (got rid of my TV and gave it away). Maybe someone from RedLynx or Ubisoft Shanghai could investigate how their game behaves under those conditions.

So slightly off-topic:
I play with Vsync off(game and forced off in driver) on a 120Hz monitor but the game is capped to 60 fps anyway.
Trials doesn't tear that much that it bothers me, so I'd rather prefer as little input-lag as possible.
Limiting the game to 58 fps+forcing Vsync to reduce the Vsync-originated input-lag doesn't work very well with Trials unfortunately use that usually when downsampling via custom resolution or when a game just exhibits horrendous tearing in general).

That said, before 1.03 the game still choked in rare cases slightly- to medium-noticeable on certain tracks or areas of tracks, MP amplified it.
And that happened with a 2600k@4.7GHz, 16GB RAM, Titan and an SSD - a system which masked those issues but they were still there.
After 1.03 I didn't notice any stuttering so far.
So even without Vsync being a factor, in my case the game had some performance issues until the latest patch came out and it might not have had the same impact for everyone as there are still users complaining.

[rlmergeuser]

That said, before 1.03 the game still choked in rare cases slightly- to medium-noticeable on certain tracks or areas of tracks, MP amplified it.
And that happened with a 2600k@4.7GHz, 16GB RAM, Titan and an SSD - a system which masked those issues but they were still there.
After 1.03 I didn't notice any stuttering so far.
So even without Vsync being a factor, in my case the game had some performance issues until the latest patch came out and it might not have had the same impact for everyone as there are still users complaining.

It's possible that the game runs a bit smoother without v-sync now than it did before. It is really smooth for me as long as I keep it off, although I do get a noticeable (but not terrible) amount of tearing. But this issue with v-sync causing intermittent stuttering is just as bad now as it was before, and this thread was me speculating a bit about why that might be. Again, I could be completely wrong, but this quote from ShiftySamurai (RL) makes me believe there might be something to it:

Trials Evolution: Gold Edition is designed to run at constant 60 FPS and the engine will skip frames if it for some reason cannot achieve this. For this reason it is advisable to run the game only with monitor’s refresh rate set to 60Hz if Vsync is enabled

60 != 59.94

[WakeXT]

It would be interesting if the Xbox 360-version runs with Vsync off or on, if it's the latter it would have the same conditions on a TV as you suggest. I also wonder what the overall majority of console games uses.

That said: Most of the time when I view game play-videos it seemed to choke from too many particle-effects, lots of moving objects or water bodies on-screen, so pretty much the same as the PC version does for some.

[rlmergeuser]

It would be interesting if the Xbox 360-version runs with Vsync off or on, if it's the latter it would have the same conditions on a TV as you suggest. I also wonder what the overall majority of console games uses.

That said: Most of the time when I view game play-videos it seemed to choke from too many particle-effects, lots of moving objects or water bodies on-screen, so pretty much the same as the PC version does for some.

Yeah, I've been wondering why the 360 version doesn't exhibit the same issues. Something must have been lost in the translation when porting the game to the PC. At the end of the day, the simple truth is that the Trials Evolution engine was originally written from the ground up especially for the 360, and deeply optimized to run as well as possible on that fixed hardware. The same care was clearly not taken when moving that code onto the PC, where different things need to be considered for optimal results.

[TeriXeri]

I noticed the "stuttering" for me doesn't actually drop fps under 60 either, I have a Monitor-TV (made for both pc and tv graphics), it happens on some tracks more then others, and multiplayer definately it happens almost once every track.

Backgrounds with a lot of fog/smoke effects seem to cause it more often,likely due to more particle effects, also clouds seem to not work well with anti-aliasing showing jagged edges.

Update: with in-game Vsync on it sits at 59.9 fps most of the time, with it off, I get major screen tearing, some tracks definately seem to have issues related to foggy backgrounds etc as trials hd tracks seem to perform much better overall.