30FPS displayed on a 200Hz monitor

AI Thread Summary
Playing an NTSC file at approximately 30fps on a PAL TV with a 200Hz refresh rate can lead to frame display challenges due to the lack of a common multiple. The discussion explores the possibility of achieving a close approximation to 30fps by displaying some frames for 6 cycles and others for 7 cycles, with calculations suggesting an average frame rate of around 30.95fps. Participants discuss the mathematical approach to determine the optimal mix of frames to minimize discrepancies without dropping any frames. The conversation also touches on how TVs handle frame rates that do not align with their refresh rates, with suggestions for potential methods to improve fluidity in playback. Ultimately, the complexity of achieving a perfect frame rate match remains a key concern.
Daveigh
Messages
5
Reaction score
0
Hello!

I have a PAL TV, and that means it is best for footage of 25fps and 50fps
The TV's refresh rate is 200Hz
Well, my questions are:
What happens if I play an NTSC file on the TV? (≈30fps), since it doesn't go well with 200Hz much (isn't a multiple)...
  • I thought about how would the TV display such files, assuming and hoping that no frames are dropped.
  • I thought that if you copy a frame 7 times at 200Hz it is approximately 28fps, and if you copy a frame 6 times, it is approximately 33fps.
  • Since the average of them is about 30.95fps, it quite irritates me, as I tend to be quite perfectionist...
  • I wanted to calculate how much frames to play at 33fps and how much frames to play at 28fps (overall in a second) to achieve the closest result to 30fps, again, without dropping frames.

I've made a sort of a assumption, which I have no idea if right or even close to reality, since my knowledge at math is quite basic.

Here is the link to all the calculations I attempted:
desmos.com/calculator/76jnihypub

I hope it is understandable enough, and since I have a tendency to confuse between cycle time and frequency, I cannot tell if what I've done makes any sense, it could be absolute nonesense...

If it is not even close, then please, I would like if someone could enlighten me and show me how should this be done.And as a side question, if anyone is familiar with this, what do TVs with various refresh rates actually do when given files whose frame rates don't have a common divisor with the Hz of the monitor?
Thank you very much!
 
Last edited by a moderator:
Mathematics news on Phys.org
Why so complicated? Let a fraction p of images been shown for 6 frames, the other for 7 frames.
Then the average number of frames per image is 6+p which means the average time of an image is (6+p)/200 seconds. This should be the same as 1/30 second, therefore 1/30 = (6+p)/200. And this has a nice simple solution.
I don't know if monitors actually do this (you can get a better (more fluent) result if you mix the two images).
 
mfb said:
Why so complicated? Let a fraction p of images been shown for 6 frames, the other for 7 frames.
Then the average number of frames per image is 6+p which means the average time of an image is (6+p)/200 seconds. This should be the same as 1/30 second, therefore 1/30 = (6+p)/200. And this has a nice simple solution.
I don't know if monitors actually do this (you can get a better (more fluent) result if you mix the two images).

B1%7D%7B30%7D%3D%5Cfrac%7Bp+6%7D%7B200%7D%5C%3B%5Crightarrow%5C%3Bp%3D%5Cfrac%7B2%7D%7B3%7D.gif
Sorry if this is a silly question, but what exactly does p stand for?
Do I have to do the same thing with (p+7)/200?
If yes what should I do after, and what in conclusion is the best average frame rate?
 
mfb said:
Let a fraction p of images been shown for 6 frames, the other for 7 frames.
I don't see where you would get (p+7)/200 from. The average number of frames won't exceed 7.

p=2/3 suggests to use 2 images for 7 frames and 1 for 6 frames. 3 images in 20 frames, or 30 images in 200 frames, which directly matches your frame rates.
 
mfb said:
I don't see where you would get (p+7)/200 from. The average number of frames won't exceed 7.

p=2/3 suggests to use 2 images for 7 frames and 1 for 6 frames. 3 images in 20 frames, or 30 images in 200 frames, which directly matches your frame rates.

Wait so this is the method you mentioned that mixes the images?
 
No. What I meant with "mixing" is something like this, but on a shorter timescale.
 
Thread 'Video on imaginary numbers and some queries'
Hi, I was watching the following video. I found some points confusing. Could you please help me to understand the gaps? Thanks, in advance! Question 1: Around 4:22, the video says the following. So for those mathematicians, negative numbers didn't exist. You could subtract, that is find the difference between two positive quantities, but you couldn't have a negative answer or negative coefficients. Mathematicians were so averse to negative numbers that there was no single quadratic...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Thread 'Unit Circle Double Angle Derivations'
Here I made a terrible mistake of assuming this to be an equilateral triangle and set 2sinx=1 => x=pi/6. Although this did derive the double angle formulas it also led into a terrible mess trying to find all the combinations of sides. I must have been tired and just assumed 6x=180 and 2sinx=1. By that time, I was so mindset that I nearly scolded a person for even saying 90-x. I wonder if this is a case of biased observation that seeks to dis credit me like Jesus of Nazareth since in reality...
Back
Top