[MPlayer-users] Q on monitor refresh rate versus fps

[Rashkae]

Matyas Sustik wrote:
> Hi All,
> 
> I do not understand the connection between monitor refresh rates and movie
> fps.  I read a few posts available in the archives but I would appreciate
> if someone could give me an unambiguous answer to the following questions.
> 
> 1.  When I play a 24fps source, how will the frames be displayed on a 60Hz
> refresh rate monitor?
> 
> 2.  Should one sync the refresh rate to the video fps?  (Multiple?)

The video driver should do this for you, if it's supported.

> 
> 3.  What does mplayer do different when playing the same video source, on
> different refresh rate monitors?
> 

This is called Vsync, and I believe it should be part of either the xv
or gl video output driver.  When working properly vsync should refresh
the video frame at an interval timed with the monitor refresh.

When Vsync isn't working, you will see tearing.  Meaning that only part
of the image is changed.  Tearing is most noticeable during horizontal
motion or horizontal screen panning, when it visibly looks as though the
image is paning one half the screen at a time.

> 4.  When purchasing an HDTV (1080p) does the 120Hz refresh rate get me
> anything worth paying for?  Note that I may be forced to use the TV through
> the VGA port since the PC-TV HDMI handshake protocol may not work.  (Oke, I
> never got it to work with my current unit despite my best efforts.)
> 

No, nothing whatsoever.  In the CRT days, a higher refresh would make
the flickering less noticeable (some people are sensitive to less than
80Mhz flicker).  LCD's don't have the same flickering problem however.
(I don't know about plasma)

> My questions are triggered by observing the playback of various video
> sources.  In particular I have a DVD (Love in the Afternoon) which appears to
> have progressive frames when I play it frame by frame (using '.').  However,
> every 4th frame is repeated, that is the fifth frame is the same as the
> fourth frame.
> 
> The movie is marked 29.97 fps so I figure that the original was recorded in
> 24fps and then to display it as 30fps every 4th frame is repeated (4/5 =
> 24/30).  I guess that then to use the 60Hz refresh rate every frame (included
> the duplicated ones) are shown twice by the hardware.
> 
> What program is doing the frame duplication?  Is it mplayer figuring out my
> refresh rate and repeating the frames?
> 

If the movie is marked 29.97, then its not progressive, it is interlaced
or Telecined.   Since you aren't seeing the interlace combing effects,
then you have some kind of de-interlacing filter going over the video.
Since you see frame duplication, I'm guessing the video is telecined,
and you are applying either the pullup or filmdint filter.  These will
restore telecined video to progressive 24fps, but causes frame
duplication when output to 30fps.

> 
> I reencoded the movie using x264 and the result again shows the repeated
> frames.  A side question is that how the duplicate frames get stored?  Is
> there just a flag indicating that there is a duplicate?  The duplicates may
> actually hurt compression, but I am not sure.  In any case I would prefer to
> encode the movie as 24fps and do the frame duplication on playback only when
> the monitor refresh rate requires it.
> 

I still think you must be getting a de-interlace filter applied
somehow,, maybe in your mplayer.conf file?  Try to encode to x264 with
-ofps 24000/1001, that should get the progressive video back to the
correct framerate (as long as the reverse telecine filter is still applied)