Why does Windows Media Player play 30fps videos at 60fps?

Question

I've tested it with FRAPS, and WMP plays 30fps videos at 60fps where VLC and MPC play them at 30fps. I would like to be able to play the video at the intended fps, is there a way to turn this off? I also installed the CCCP codec if that is of any relevance.

Solution

In most cases, with played back video, or even video game rendering, playback uses something called VSync (Vertical Synchronization) where the video is being rendered or played back as it should but the player is syncing with your monitor's refresh rate (99% of the time which is 60Hz, or 60 refreshes per second). FRAPS may simply be reading the vsync refresh, not necessarily the actual playback speed of the video. Unless the video looks like it is running at double speed, then it is most likely still playing back at 30fps.

Comments

[Psycogeek]

are the videos interlaced or progressive?

[xsdf]

I don't know, is there a good way to tell?

[Psycogeek]

Different programs will show the interleave that exists (every other horizontal line) during high movement, when you freeze frame the picture. Mabey some code in the header. I am not sure if MediaInfo (a program that reads header info) would display that info. It was always something I could see in how the motion is acting, more half frames per second? and freezing it how you can see it is 2 interleaved pictures (feilds). Some programs will toss interlace and show psudo progressive, and some programs when freeze framing will freeze feild, which is 1/2 res.

[Psycogeek]

With the Old CRTs , the scanning was done by drawing every other line , to present this eye trick to the viewer. A computer would have to change 1/2 the picture in a 60th in similarity. For an LCD monitor which doesnt "scan" it would have to display a new picture every 60th of a second, with 1/2 of it changed. Mabey the reason they mostly gave up on the idea is my poor explainations :-)

[xsdf]

ok so then am I just to assume all data from FRAPS for WMP is going to not really represent the play back. And if so how can turn off the VSync, if at all possible?

[Psycogeek]

Vsync is adjustable in the application EX: many games would allow for the Vsync to be changed in the video or graphics options. Vsync can also be changed and locked manually or set for application control in the 3D options of the display device. EX: in ATI/AMD you would go to CCC (the GPU controls) and Find the 3D section and change the Vsync options.