I was having issues with video playback of large (nearly 4k) videos.
Part of the video was tearing, I knew the hardware was capable of playing the video ok, but in several applications the video would having tearing and playback performance wouldn't be very good.
After extensive trial and error, we determined the cause was the fact that we had switched off windows themes.
The machine in question was running Windows 7 Professional.
We tried this on a few other computers around and found the same thing. We had to switch themes back on to make the video play back reasonably.
We were able to turn the themes service back on and off and each time consistently see the video play poorly with themes off and then dramatically improve when switched back on.
I (perhaps naively) assumed that the themes service was purely responsible for the visual styling of GUI elements. Clearly this isn't all the W7 themes service does.
I can not find via google or microsoft.com a complete description of what the themes services is responsible for.
Does anybody have -
1. Any idea why themes service being on would improve video playback ?
2. A complete description of what the themes service does ?
edit- in case it matters the video format was MP4 h.264, we tried both the build in Microsoft decoder, as well as LAV.
Answer
Vsync is usually the reason for tearing.
Vsync in Windows Vista and later is handled by the desktop compositor and video applications. With classic theme, screen drawing reverts to GDI (think Windows XP but worse) where there is essentially no control over vsync. Nvidia driver will only force vsync in D3D or OGL applications.
The solution in this case is to enable vsync in your video application. If your current video application doesn't support vsync, get one that does. As far as I'm aware, that feature is for example supported in Media Player Classic Home Cinema.
You should also check if the video settings for refresh rate or frame rate are different
when aero or classic are on.
No comments:
Post a Comment