Question

Note: This might seem like a Super User question at first, but please read it completely — it’s a programming question.

---

So they removed GDI acceleration from Windows 7, and now the classic theme animations look horrible. And because it was a fundamental design change, there’s no way to fix it, right?

Wrong!

I was really surprised today when I switched to Classic view (which turned off Aero) when VLC media player was running. Normally, the maximize/minimize animations look horrible (they barely even show up), but while VLC was running, the animations were perfect, just like on XP! As soon as I closed VLC, they became horrible again. (They were better when media was playing than when the player was idle.)

I’d reproduced this sometime before when I’d fired up a 3D game and noticed that the animations had improved, but I’d assumed that it it had been a DirectX-related issue. I’d tried to figure out which function calls had caused the improvement, but with no luck. So I was really surprised today when I noticed the same behavior with VLC, because it was not playing video, only audio (not even visualizations!) — and yet playing audio improved my GDI graphics performance, making me think that maybe, just maybe, Windows 7 does have some sort of GDI acceleration after all. (?)

In the case this makes a difference, my graphics card is an NVIDIA GT 330M, and PowerMizer is off. I’ve controlled for every variable I can think of except for whether or not VLC was running, so I can pretty much rule out anything related to features of the graphics card.

---

So, now for my question:

Does anyone have any idea which API call(s) might be causing this improvement, and whether they are actually related to graphics or not?

I’ve tried making a program that calls IDirectDraw::CreateSurface and simply runs in the background (hoping that it would do the same thing as my 3D game did), but no; there wasn’t any difference. I’m not even sure if it’s a graphics-related API call that might be causing this, since like I said, VLC was playing music, not video. It’s a mystery to me why the performance would improve when a multimedia app is running, so any insight to what’s going on inside this would be appreciated. 🙂

Answer 1

It could just be a factor of the system clock tick period. Running VLC probably changes the clock tick to every 1ms, causing the animations to run more smoothly.

Use Clockres to check the system timer resolution with and without VLC running to see if it’s making a difference.

See the timeBeginPeriod function for how to set the time period yourself. Keep in mind that the shorter the period, the less time your CPU will be able to sleep between ticks, and the hotter it will run.