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Interlacing Bug in Software Mode with Constant Frame Skipping
#1
Bug 
Hello forum!

Recently I have tried to play Fallout: Brotherhood of Steel on PCSX2. The well known bug with half-screen black is solved by using Software Mode, but the image is "shaking" during gameplay and needs to be deinterlaced...

After all I got an "overlapped" bug - from time to time the current image "saves" in the interlacing overlay and stick on the screen. It happens regulary, but not systematically... Smile

Screenshot of the bug:
[Image: 315271e.jpg]

I made an animation to make it clearer:
[Image: 2u7neoj.gif]

My GS settings (every second frame is skipped - gives best performance on my machine):
[Image: 2nb5894.jpg]

My Gsdx9 settings (weave bff deinterlacing used):
[Image: 35cg9cg.jpg]

My rig:
- Intel Dual Core E5200 @ 3GHz
- 2 Gb DDR3
- Ati 5570 1 Gb @ 700 / 950 Mhz
- Windows 7 Home Premium

Sorry for my English, it's not my native language.
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#2
that's actually the normal effect of skipping interlaced frames. i don't see any bug there. the frozen frame is the one that is skipped to be rendered with actual data. the effect that it switches sometimes is due to ps2 internal framerate issues flipping the interlaced frame.

actually the trick to solve this is whether skip or draw even frame numbers, like 2, 4, 6 while the other value is uneven like 1, 3, 5. the effect is that the skipped interlace field changes every couple frames when rendering. it may cause some "freeze bug stop motion" but it's not doing that frosty frames you posted there.
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#3
(11-20-2012, 02:43 PM)xstyla Wrote: that's actually the normal effect of skipping interlaced frames. i don't see any bug there.
If this is not a bug, when why it appers so suddenly?! Some times the screen just black after enabling Skipping Frames.

(11-20-2012, 02:43 PM)xstyla Wrote: the effect that it switches sometimes is due to ps2 internal framerate issues flipping the interlaced frame.
May be some hack to make this interlaced frame black or something?

(11-20-2012, 02:43 PM)xstyla Wrote: the trick to solve this is whether skip or draw even frame numbers, like 2, 4, 6 while the other value is uneven like 1, 3, 5.
I played with numbers, tried both even, like default 2/2, even/uneven and vice versa pairs, in this cases the image is twitching and gameplay becomes very unplesant. The 1/1 pair is providing ~30fps, which gives smooth and cheerful gameplay.

May be exists another method to achieve 30fps from default 60? Changing NTSC/PAL thresholds is working in wrong way, the game becomes even more sluggish. In MKA, for example, it makes gameplay like underwater. Laugh
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#4
Speedhacks and frameskip can be seen as one as well are attempts to get the machine at correct FPS or near it.

But they may introduce problems (not only in the graphics but mainly in the second case). you'd be actually running the game at 30 samples per second (although the FPS would near that desired 60).

1:1 is a really strong level of skipping and almost every game will present serious issues with it. If absolutely needed you could try 2:2 for despite being the same ratio it would draw the 2 frames needed for the interlace and skip the two following frames.

Anyway, that hardly would represent a good solution and no, it's not a bug in that specific case, the machine is just not powerful enough to run as the emulation request. And depends on the game being played and not the emulator alone.

The problem with the half screen is already a symptom that game is highly misbehaving even with the emulator not resourcing to any these hacks.

There is a bug indeed but is the half image and one that possibly will not be addressed that soon.
Imagination is where we are truly real
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#5
Would you prefer if the frameskip options were removed? It's a hack, which means it's intentionally taking shortcuts or performing other tricks in the hope that it might help on some cases, but it WILL break some games for sure. Interlaced games are one of those cases for which frameskip doesn't work well, it would appear, so just don't use it with them.
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#6
Thumbs Up 
(11-20-2012, 11:19 PM)nosisab Ken Keleh Wrote: 1:1 is a really strong level of skipping and almost every game will present serious issues with it.
At 30 fps (1/1) all motion in games looks smooth enough, 60 fps is not necessary, IMHO, but 15-20 fps (2/2) makes game very tearing.

(11-20-2012, 11:19 PM)nosisab Ken Keleh Wrote: If absolutely needed you could try 2:2 for despite being the same ratio it would draw the 2 frames needed for the interlace and skip the two following frames.
I have tried already. The results are not as good as when 1/1, the picture is twitches and playing is not so pleasant, but... it seems I'm accustomed. Rolleyes

(11-20-2012, 11:19 PM)nosisab Ken Keleh Wrote: There is a bug indeed but is the half image and one that possibly will not be addressed that soon.
AFAIK, this bug is engine-dependent and appears in another game or two. I believe the engine draws left and right parts of the screen alternately, may be this is a interlacing method...

(11-20-2012, 11:47 PM)avih Wrote: Would you prefer if the frameskip options were removed?
No, absolutely no!
Something wrong happens with only one frame out of the bunch and this frame can be just skipped, the player will not even notice that loss.
The problem is how to identify such a frame... I think this "bug" can be reproduced in debug mode by one of the developers and reason will be found, am I right?

(11-20-2012, 11:47 PM)avih Wrote: Interlaced games are one of those cases for which frameskip doesn't work well, it would appear, so just don't use it with them.
Unfortunately, the quantity of "interlaced" games is much bigger, than with progressive scan.

Thanks to all for quick replies.
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#7
Also you can give an attempt and try that:

Code:
// Force Alternate Rendering Mode
patch=1,EE,201B8170,word,24120002
patch=1,EE,201B87A8,word,0803FFE0
patch=1,EE,200FFF80,word,3C010003
patch=1,EE,200FFF84,word,0061182F
patch=1,EE,200FFF88,word,FCA30000
patch=1,EE,200FFF8C,word,0806E1EB

You need to make a normal boot for this to take effect, don't load a savestate, it won't work.
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#8
(11-21-2012, 02:18 AM)VIRGIN KLM Wrote: Also you can give an attempt and try that...
Nope, hangs up after language select, just before memory card check. Anyway, thank you for help!

Have tried 1/1, 2/2 and disabling frame skipping, result the same - black screen. Even has disabled all speed haks and changed VU0/1 recompilers - no difference.

With 2/2 frame skipping I noticed flickering of sprites over video, what PS2 uses frequently in games, like this:
[Image: zx4fgx.gif]

Nothing can be done about this? "Switch to GSdx sofware rendering when a FMV plays" hack already checked.
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#9
(11-21-2012, 02:14 AM)antaurus Wrote: At 30 fps (1/1) all motion in games looks smooth enough, 60 fps is not necessary, IMHO, but 15-20 fps (2/2) makes game very tearing.

I have tried already. The results are not as good as when 1/1, the picture is twitches and playing is not so pleasant, but... it seems I'm accustomed. Rolleyes

AFAIK, this bug is engine-dependent and appears in another game or two. I believe the engine draws left and right parts of the screen alternately, may be this is a interlacing method...

No, absolutely no!
Something wrong happens with only one frame out of the bunch and this frame can be just skipped, the player will not even notice that loss.
The problem is how to identify such a frame... I think this "bug" can be reproduced in debug mode by one of the developers and reason will be found, am I right?

Unfortunately, the quantity of "interlaced" games is much bigger, than with progressive scan.

Thanks to all for quick replies.

Don't confuse PC games where the synchronization is done in real time with console (TV standard) where it is done by frame. But is not what I meant, you'd still have 60FPS just than not actually processing the even frames (just replaying the odd ones or skipping the calculation of frames second the chosen ratio). If even with all these hacks you can't get near 60FPS, it is helpless. That's one the reasons for the flickering you see there.

What was already said is you'll not going to get that game playable as you want so soon. Refer to this link and see what I mean.

http://pcsx2.net/compatibility-list.html?letter=F

It's already not working even if no hack at all is applied... with hacks you can only expect things to be worse yet.
Imagination is where we are truly real
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#10
(11-21-2012, 03:32 AM)antaurus Wrote: Nope, hangs up after language select, just before memory card check. Anyway, thank you for help!
Which version of the game do you have?
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