Out of curiosity, what's the need for setting refresh rate to 24Hz?
It's basically because he's in PAL-land. The standard Frame Rate for film is 24fps. PAL uses a standard frame rate of 25fps (progressive) or 50 fields/sec (interlaced). Unfortunately, unlike with NTSC, this means there is no easy way to convert the video signal to 24fps. The result is that either: (a) you run content that was designed for 24fps at 25fps (which makes everyone go a little faster than they are supposed to), or (b) you do fancy retiming in software. Jmone experienced a common problem with option B in that he experienced significant "telecine judder" (unsmooth motion, especially noticeable with medium speed pans and other similar effects).
Those of us in NTSC-land (US, Canada, and Japan among other random countries) don't have as many issues with this because our "pulldown pattern" used to convert 24fps to 29.97fps is much simpler. A standard NTSC TV runs at 29.97fps (progressive) or 59.94 fields/sec (interlaced). To display 24fps content on these televisions, you can use a simple 3:2 pulldown pattern. This is accomplished in two steps:
1. The film frame rate is dropped slightly to 23.976 fps. This change is imperceptible from the original 24fps footage.
2. 3:2 pulldown is added to convert 23.976fps film to 29.97fps video. You may have noticed that 23.976 is exactly 4/5 of 29.97. This works out well, and allows you to exploit the interlaced nature of video to correct for this frame rate difference. It works like this:
Say you have 4 frames of film, which you want to transfer to video (obviously you would have a lot more than 4 frames, but keeping the example simple). These frames can be labeled A, B, C, D. Now, because video is interlaced, it actually has fields, not frames (the first field from each frame is all of the odd numbered lines, then the next is all the even numbered lines). So, what you do is you transfer those 4 frames of film to 5 frames of video by repeating a couple of fields in a 3:2 pattern, like this:
Video Frame 1 Field 1 = Frame A
Video Frame 1 Field 2 = Frame A
Video Frame 2 Field 1 = Frame A
Video Frame 2 Field 2 = Frame B
Video Frame 3 Field 1 = Frame B
Video Frame 3 Field 2 = Frame C
Video Frame 4 Field 1 = Frame C
Video Frame 4 Field 2 = Frame C
Video Frame 5 Field 1 = Frame D
Video Frame 5 Field 2 = Frame D
As you can see, after this fourth original frame, you've "fixed" the cycle (the original frame begins and ends in the same video field) and you can go back to the beginning of the pattern and start over. It basically just repeats this pattern over and over. It does make every other frame of video last a tiny fraction of a second longer than it "should" but because the TVs are interlaced you can't tell (because those elongated frames are "mixed" on screen with the proper frame).
Then, if you have a progressive scan TV and/or DVD player, it knows how to recognize this pattern and remove it to display only the original pristine frames. This is known as "reverse telecine". It simply recognizes and discards the mixed frames and only plays the proper frames as they were originally shot.
However, when you're in PAL-land, everything isn't so easy. To accomplish the same effect for PAL, they need to use a pattern called
2:2:2:2:2:2:2:2:2:2:2:3 pulldown. As you can probably guess, this is far less ideal and a lot harder to accomplish effectively. It essentially makes every 12th frame display for 3 PAL fields. Unfortunately, because of PAL's lower interlaced speed (50 vs. 59.94), the effect is far more noticeable. Also, reverse telecine requires much longer framebuffers (12 frames rather than only 5), which means you need higher-end hardware. As you can probably guess, it is less effective (due to cheap hardware)...
In the old days of PAL, they used to just run all 24fps content at 25fps. This eliminated the need for fancy conversion and more expensive hardware, but it makes everyone run a little faster, and more disturbingly it makes the audio a little higher-pitched and faster. So, if you don't want everyone to sound a little like Alvin and the Chipmunks, you need to do the above pulldown system...
So, to remove the need to do any of this, you can run your display at 24fps (assuming you have a monitor that can do that refresh rate). Running at 24fps isn't ideal for most other fast-motion though, as it will make fast animations and other on-screen effects look "jerky" (ever notice that no one does really fast pans in movies? That's because of the low 24fps frame rate!). It also looks terrible with other fast-motion content recorded at high frame rates (especially sports). So, unless you switch your monitor back and forth, your stuck with either (a) bad fast-motion, or (b) bad movie framerate conversion.
Make more sense?
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Topic: What Can I do in 5 Days with my new BluRay / HD-DVD Drive & MC12?? (Read 3994 times)