MacBook Pro 1080p 24hz?

Discussion in 'Mac Basics and Help' started by AaronChiles, Feb 26, 2008.

  1. AaronChiles macrumors newbie

    Feb 7, 2008
    Raleigh, NC
    I have a MacBook Pro with the 8600GT 256mb and a Westinghouse TX-42F430S 42" LCD with HDMI that supports 1080p/24hz.

    I was wondering if any of you know how to output 24hz via DVI? It only comes up with 60hz when I plug it in, yet my TV supports 24hz. Is there anyway to set a custom refresh rate? I am really new to Macs.

  2. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    60hz is the correct refresh rate (because it's just a convenient setting; a holdover from CRT days). By "24hz" you mean 24fps, and you wouldn't want 24hz for the connection anyway. With refresh rate, higher is better, not lower. 24hz would be roughly equivalent to 42ms pixel shift. Actual displays are typically 12-16ms, with lower being better.

    You don't need to change that setting; the TV will handle the 24fps content the same way it would from a DVD.
  3. AaronChiles thread starter macrumors newbie

    Feb 7, 2008
    Raleigh, NC
    Yeah higher is better, but I'm trying to achieve 24hz 48hz or 72hz. Since movies are shot in 23.997 fps, the new TVs (some support 120hz) display the best picture that way because their is no 3:2 pulldown conversion. I can see the lag on 60hz when the camera pans across something and I'd just like to eliminate. I'm more concerned about if it is possible to do in OS X, or if I'm going to have to do it via boot camp. Thanks.
  4. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    You can't.
    You're confusing refresh rate and frame rate. A television is not a film projector. No LCD or plasma TV can do what you're asking, and neither Windows nor OS X will give you that option. Pixel shift will automatically slow to compensate for the change in content for the frame rate; LCD and plasma televisions are not "redrawn" and cycles-per-second refresh rates are meaningless.
  5. tangles macrumors member

    Jul 1, 2008
    24hz output is definitely possible to LCD/Plasma

    Hi Matticus,

    24Hz certainly is a valid output option. As long as your LCD or Plasma display can accept it.
    Be careful though, some manufacturers claim to be able to receive a signal of 24Hz, which they do, but they also convert to 50/60Hz on the fly, which is where the 3:2 pulldown is applied.

    I have a Sharp 42" LCD Display that happily accepts a 24Hz signal without any on-the-fly conversion, from my MacPro. It's just a pity that I have to use Vista and ATI Catalyst drivers to achieve it.

    Viewing a Matroska file encoded at 23.97/24 fps is a fantastic experience when output to my Sharp display at 24Hz.
    No 3:2 pulldown fields being repeated whatsoever, and so a smooth flowing image results.

    To say that higher is better is just well, plain silly. The key to any viewing setup is to "match" the source from start to finish.
    e.g. if you have a DVD (basically all are re-encoded to NTSC or PAL by the way) which are 25fps for PAL SD or 29.97fps for NTSC SD, then a display that can output 50Hz and 60Hz respectively, is desirable.

    Nowadays, some LCD displays are being manufactured with even greater refresh rates. Sony have just released a 200/240Hz LCD display. What this basically means is that if you have a PAL SD source (say a DVD) which is 25fps, then the Sony LCD display will simply add 4 fields for 100Hz and 8 fields for 200Hz, iinto each refresh of the display. (assuming the Sony display is set to receive a PAL signal of 50Hz)

    Oh, and 120Hz is divisible by 24, therefore a Matroska file with 24p encoding, when sent to my Sharp LCD will fill in 5 fields per frame per refresh cycle, hence no added fields causing the dreaded stutter effect.

  6. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    No, 24fps is a valid output option. 24Hz is not valid. A flat panel display will always output at 60Hz or 120Hz, depending on which technology you have.
    If you are outputting on a stock video card, it's 60Hz. Always. The signal clock does not change. There are indeed models that can output 24fps content without telecine, but that is a totally separate question from the signal clock.
  7. tangles macrumors member

    Jul 1, 2008
    Well of course all LCD displays output 60/120/240 for NTSC or 50/100/200 for PAL regions. I thought this was a no-brainer and assumed by everyone... (so I thought).

    This whole thread is about accepting a 24hz signal, adding fields per frame to pad out the signal/feed, to avoid the dreaded 3:2 pulldown: when being viewed on LCD panels with the above signals...

    And over the break I successfully got my MacPro to output a 24hz signal! Yay for me!!
    So I apologise to Apple, but wish it were a bit easier to achieve.

    This is what I did to achieve it.

    Had to use Micro$loth Windoze so bootcamp etc is necessary. (don't think VMs get direct access to video so I'm not sure if a VM would work, confirm anyone?)

    I have a Radeon 4870x2 in my MacPro and so I used the ATI/AMD Catalyst 8.11 which has a 1920x1080 24Hz as a choice in the drop-down resolutions.
    I have a Sharp Aquos LC42D83X connected.

    This however did not tell me the necessary information that SwitchResX requires, such as:
    • Active
    • Scaled
    • Sync
    • Porches
    • Frequencies, or refresh rates
    • Pixel clock
    (as per

    This is where PowerStrip for Windoze comes in.
    It's shareware, but you don't need to pay to attain the above values.

    Using this, I took a screen shot (or just write down the values).
    Boot back into OSX and launch SwitchResX. (you only need the control panel, not the full app by the way to achieve this)
    I created a custom resolution with the new values.
    Reboot and hello, the 24Hz appeared in my System Prefences -> Displays pref pane.
    Selected it and sure enough, my Sharp LCD Panel popped up it's source-signal-overlay text thingy and informed me that it's receiving a 24hz signal.

    First thing I obviously did was launch VLC and tested it out with some 24p footage..... marvelous! no more judder/stutter annoyances. Gone forever.

    So, anyone should be able to repeat this for their specific LCD Panel.
    I'm at work atm but I'll post the actual SwitchResX values for others who might have the same LCD panel as me.

    cheers all.
  8. SnowLeopard2008 macrumors 604


    Jul 4, 2008
    Silicon Valley
    Why would you decapitate yourself with slower refresh rates?
  9. tangles macrumors member

    Jul 1, 2008

    have a read of wiki's explanation and use of 24p.

    I can notice a "flicker" on the screen, but only really if I look away from the screen or when the screen is in my peripheral vision.

    I much prefer the "24p film" effect over the stuttering "3:2 pull-down" effect any day, to the point where I used to boot into Vista to watch anything 24p, it jacked me off that much!

    I'm about to write some applescripts to toggle my setup between 24Hz, 50Hz and 60Hz so I can use my Dvico Remote, and have my HTPC and Sharp display match the source file I wish to play/watch.

    (Thanx again to Peter for writing the Dvico OS X driver too)
  10. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    What you're missing is that while the Westinghouse the OP mentioned supports 24fps inputs, it is not a 120Hz display and thus cannot operate at "24Hz".
    That's not how it works--you're describing interlaced telecine. A 24fps source will, in displays that support true telecine-free film modes, simply repeat the same frame to match the display. This requires a 120Hz HDTV. 60Hz HDTVs, or in other words nearly all of them, simply cannot do this, whether they accept the input or not.

    Just like many 720p HDTVs will accept a 1080p input, many 60Hz displays have a 24fps mode which will also duplicate frames and not fields (but progressively), resulting in somewhat smoother motion than the basic 3:2, but it's still a telecining technique and not all frames are displayed for the same amount of time, so it is not displaying anything at 24Hz or any multiple thereof.
    Well, you mean no noticeable judder from 3:2 telecine effects. There is still uneven motion from the film mode and you still have to contend with the source material, some of which is filmed with judder as part of the presentation.
    Your display is 100/120Hz, so that would work fine for you and others with such a set, but not for the OP and his 60Hz LCD.
  11. davidrools macrumors newbie

    Jan 27, 2009
    What you say was true a couple years ago, but is no longer the case. LCD panel manufacturers have responded to customer demand to avoid 3:2 pulldown and have developed sets that DO down-clock the signal sync to accept a 24hz refresh rate signal and display 24 unique frames per second. My Sharp D64U panel clocks down from 60Hz to 48Hz and it is clearly evident that it is not simply accepting the 24hz signal and displaying at 60hz (side by side comparisons make the 3:2 pulldown's effect even more noticeable)

    Here's a list of displays that can adjust their display signal clock to 48, 72, 96, or 120hz.

    Yes, the OP's set accepts a 24Hz signal but cannot display anything other than 60Hz. I think you've corrected yourself by your last post. However, a 120Hz maximum refresh rate is not necessary as some lower-refresh sets can down-sync.

    You're dead on with the fact that displaying 24 frames per second will make fast motion look choppy. That's the limitation of filming at 24 frames per second. Motion-enhancement on some sets will try to draw unique intermediate frames between the source frames, which will produce some softness similar to 3:2 pulldown but also retain the original source frames (unlike with pulldown).

    Personally, what displaying at 48Hz does for me is to greatly improve the sharpness that is lost with 3:2 pulldown. I actually see MORE judder at 48Hz than at 60Hz, since the pulldown also has a bit of a smoothing effect, believe it or not. Still, 48Hz matches theater projector refresh rates and is my preferred setup for watching blu-ray discs.

    Speaking of blu-ray discs, there's really no reason to try to achieve syncing a 24Hz signal between a computer and a display unless you're watching a blu-ray disc or a (most likely illegally obtained) 24fps encoded video file. Last time I checked, too, MacOS didn't support playing blu-ray discs, so you'd have to be booting to Windows anyway. DVDs are encoded in PAL/NTSC, as a previous poster mentioned.

    I'm confident that in the next few years, cinema will convert to digital 1080p/60Hz filming equipment and this whole discussion will be for not. Cinema projectors will be digital and match the same 1080p/60Hz input with equal output. But for now, 1080p/24, 72, 96, 120, or 240Hz is the way to go!
  12. 7031 macrumors 6502


    Apr 6, 2007
    Really? While 60Hz may be better in some respects, I feel that the 24Hz rate helps give films that unique look.
  13. matticus008 macrumors 68040


    Jan 16, 2005
    Bay Area, CA
    No, 24Hz continues to be invalid. As you correctly point out, there are panels that can vary their displays to multiples of 24, but you are still referring to a 24fps mode and not a 24Hz signal clock, which simply does not exist, and would have serious stability problems if it did, as the electronic switching used in VGA and TMDS-based transmission systems is designed for a specific frequency band.

    I did not discuss the 48Hz models for simplicity's sake because it was clear the OP did not have one--his LCD would be, and always remain, 60 or 120Hz, depending on the model. As it turned out later, his was a 60Hz set.
    Yes, that is indeed an omission from my first post. Such displays are so rare (indeed the list you link only refers to four models with such a mode of the hundreds supporting a 24fps-compatible mode) as to not really need mentioning with the introduction of 120 and 240Hz panels, but in the interest of precise accuracy, you are correct.
  14. Mr Dobey macrumors 6502

    Aug 8, 2008
    Still confused

    I see what you mean by always remaining at 60Hz because at the back panel of my tv it says ~120V 60Hz

    But I am still confused as you can see from the attached photo of my setup, what exactly is being presented at 24Hz?

    Toshiba REGZA 32RV530U
    MacBook Pro
    via DVI to HDMI

    While watching a 23.976fps Blu-Ray rip via Plex the movie looks almost identical on 24Hz or 60Hz. The only difference I see is that movement on everything else (like mouse movement and selecting a window) is very very choppy at 24Hz.

    Attached Files:

  15. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    These numbers have absolutely nothing to do with the refresh rates being described in this thread; that 60Hz is the frequency of the AC electricity your TV gets from the power company, not the refresh rate of the display panel. They're just both measured in cycles per second (Hz), and are both 60 (not a coincidence; the broadcast TV standard was originally designed to match the frequency of the power, to reduce visual distortions on old TV sets).

    My guess is you're not noticiing a difference because you're just not sensitive to judder, though it could well also be because of something the Mac is doing "wrong" displaying the signal (although the fact that it offers 24p for output implies it should work properly).

    I'm not well-enough-versed to try and give a good answer, though. I will note that this thread started two years ago (not that all that much has changed since then).

    Also, I recently tested a clip of 60p video on my MBP (true 60p; it was a tech demo some website was experimenting with), and Quicktime was definitely capable of displaying it properly--it looked almost weirdly smooth, though quite pretty.
  16. Mr Dobey macrumors 6502

    Aug 8, 2008

    Well at least the 60Hz on the rear of the TV question is resolved.

    I'm still a little surprised that the 24Hz makes the movies look slightly better but the mouse movement incredibly choppy.

    Makosuke, when you were describing how true 60p video looks almost weirdly smooth it reminded me of a particular scene I came across when I was watching the Blu-Ray 'Kingdom of the Blue Whale'. All through the movie I could see jutter when viewing high motion scenes like water splashing. But than there is a 10 second clip of a tanker ship that you can tell was shot with a different camera. For these 10 seconds the motion looked so smooth that it was almost fake. Could it be possible that the movie switched to a different higher frame rate than 24p? The smooth playback looked similar to a demo Blu-Ray unit on a new 240Hz TruMotion screen at the stores. I've now seen 106 Blu-Ray titles with my TV connected to my PS3 and this is the only time I've encountered this.

    What's going on and how can I see more movies this smooth : )
  17. tangles macrumors member

    Jul 1, 2008
    If your display is 100/120Hz capable and accepts a 24p signal without converting it on the fly (i.e. 3:2 pulldown), this is what happens:

    The source (BD player, Mac etc) sends a 24Hz/24p signal.

    Your display accepts the 24Hz/24p signal and displays a single frame 4 times before refreshing the screen and moving onto the next frame. This is known as a field.

    So: 24 frames x 4 fields = 120. (aka: 120Hz)

    Your display never actually (physically) changes its refresh rate... it remains the same at 120Hz. It simply pads each cycle by 4 fields when receiving a 24p input.

    This is why you notice a "choppy" mouse because your display is only updating the mouse coordinates 1/4 of the time when receiving a 24p input.

    I hope this makes sense to you.

    And all of this matters, only if you notice that slightly annoying, painful, frustrating, infuriating 3:2 pulldown effect. LOL

    if you don't notice it... (most don't until it's pointed out to them, then you can't help noticing it at other people's houses) then don't worry about adjusting anything... :D


    Because I live in australia, we receive MPEG2 TS at 25 fps interlaced at approximately 12 to 14 MBit/sec... It's rather average... and wish we had MPEG4 Part 10 down here!!

    Anyway. To watch tele, I set my Sharp display to 50Hz. Therefore it pads each refresh-cycle by 2 frames to equal 50Hz... with me? (I also have EyeTV convert the interlaced feed to progressive, so EyeTV creates a 50p signal from a 25i source (with a bit of softness due to ripping the interlaced stream apart)

    With 10.6.2 out now... I don't need to hack/apply anything with my MacMini 2009. It auto recognises when a display is 24p capable, so I don't even have Vista installed anymore... (yay)

  18. Mr Dobey macrumors 6502

    Aug 8, 2008
    Thanks a bunch.

    Just found the specs on NewEgg and it says video scan rate is 60 Hz.

    With this info, there will never be a way for me to avoid 3:2 Pull down correct? because 60 is not a multiple of 24.

    Just to clear things up in my own mind, When I select 24 Hz from the display preferences in Mac OS X I am not changing any settings on the TV, just the output rate of my computer right?

    Also, since I'm watching 24p, would it be easier on my processor to output at 24Hz than 60Hz? I need all the spare processing power I can get.

    Soooo possibly the extremely smooth video I was talking about earlier could of been shot in 30fps????

    So: 24 frames x 4 fields = 120. (aka: 120Hz)"
    you mean 24 x 5 = 120 right?

    Thank You for all the insite : D
  19. tangles macrumors member

    Jul 1, 2008
    Correct.... any 50/60Hz display that accepts a 24p signal must apply 3:2 pulldown to fill in the fields...

    Correct. you display only ever outputs/refreshes it screen at 50Hz or 60Hz. It's just capable of receiving different frequencies...

    mmm, this one I'm not sure of...
    But if you have a 60FPS source and output at 24Hz, your computer still needs to decode the file fully before display anything... so I'd imagine it would not be beneficial to go down this path.

    Here are some good references/reads for you, that I occasionally go back to as "refreshers"...

  20. Mr Dobey macrumors 6502

    Aug 8, 2008
    Since we've been talking about sending a DVI signal to a TV this whole time, does everything stay true to a computer display also?

    For example, I put a 1920x1200 LG screen in my MacBook Pro, and the only frequency it will run under in Snow Leopard is 56Hz using SwitchResX. If I have all my details straight, the screen panel will always run at 60Hz, I'm simply feeding it a 56Hz signal from the OS right?

    I could imagine there must be some bad match up going on since the movie is 24fps, signal is 56Hz and the screen 60Hz.

    I attached a screen shot and EDID Profile if that helps at all.

    After all this new knowledge I want a 120Hz Laptop display to be released : (
    A 15" MacBook Pro with a Blu-Ray drive, 120Hz WUXGA Screen and HDMI, We can dream right?

    Attached Files:

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