Frame Rate Bug

Background Information

In Windows Vista and Windows 7, there is a particularly annoying Windows Media Center bug that affects certain interlaced (480i or 1080i) video. Essentially, Media Center "thinks" that the video is rapidly toggling between interlaced and progressive scan. As a result, Media Center causes your video card's hardware deinterlacer to reinitialize over and over again. Whenever the deinterlacer has to restart, a variety of side effects will manifest. The most common effects are:

Stuttering or Juddering Video
Screen Blanking
Flickering or Strobing Video

This bug has been noted to affect both ATI and Nvidia videocards -- particularly newer cards (circa 2005 or newer) with more advanced on-board video processing features.

The bug only affects interlaced scan programming (CBS-HD, NBC-HD, CW-HD, Digital Standard Definition Programming).

In addition, only certain television shows will be affected by the bug. In general, affected content was originally filmed at 24fps. This includes movies and most prime-time HD programming. Sporting events, reality shows, news, and late-night talk shows are generally NOT affected by the bug.

And, to complicate things a little more, the bug is also dependent upon encoding methods used by individual broadcast affiliates. So, some guy in Memphis might have stuttering video due to the Frame Rate Bug while watching "The Office" on a Thursday night. Meanwhile, someone else in Detroit might not encounter the bug while watching the same airing of "The Office", because his NBC affiliate is using a different video encoding method than the Memphis NBC affiliate.

Diagnosing the Frame Rate Bug

Now, there are several things that can cause the symptoms listed above. Poor antenna signals, excessive hard drive activity, or network congestion (if you have a networked TV tuner like the HD HomeRun) can cause some or all of these symptoms. Here's how you determine if you have the Frame Rate Bug.

Start watching a program that exhibits any of the three symptoms listed above. You can either watch as Live TV, or play back an affected Recorded TV program.
On your remote, press the following keys: "4", "1", "1", "Info". You should now see a diagnostic table overlaying the playing video.
Press the "right" key several times until the header of the window reads "DEBUG: Presentation".
At the bottom of the Debug window, there will be an item called "Frame Rate". Watch this value. If it frequently bounces between 59.9401 and 29.97, then you are affected by the Frame Rate Bug.

The Symptoms

1. Stuttering or Juddering Video

More info coming soon...

2. Screen Blanking

More info coming soon....

3. Flickering or Strobing Video

The video below demonstrates the flickering or strobing effect associated with the Frame Rate bug in Media Center.

If you have an ATI video card, this can be fixed by disabling Dynamic Contrast in Catalyst Control Center.

If you have an Nvidia video card, you may see similar flickering if you've made significant changes to the color settings from within the video drivers. In this case, the flicker can be remedied by setting the Nvidia Color Adjustment settings to "Use Application Settings".

Whenever the Frame Rate Bug forces your video card's deinterlacer to reboot, any color settings applied within the drivers will be turned off for a frame or two. The result is the flickering effect seen above. The solution is to make sure that your video card's color settings are as close to the defaults as possible.

Home Theater PC