CurtPalme.com Home Theater Forum

[kal]

HOME THEATER QUESTIONS & ANSWERS

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Q: What's 1080p/24? Is it possible on CRT projectors? Does the Moome Sony IFB-HD HDMI card support 1080p/24 directly from a Blu-ray player to the projector (Sony G90 in my case)?

A: HD DVD and Blu-ray films are stored in 1920x1080 resolution at 24 frames/second (or Hz), referred to as 1080p/24. Film is shot at 24 frames/second so this is the 'native' rate of film.

The Moome Sony IFB-HD HDMI card does permit you to use 1080p/24 direct from a Blu-ray player. See the user manual available in the IFB-HD FAQ thread in our forum. However, (and this is important) you cannot use 24Hz refresh rate on any CRT projector or analog display device as the refresh rate is simply too low and the flicker that results from only refreshing the image 24 times/second is unbearable to watch. Many analog displays and CRT projectors will not sync as low as 24Hz refresh rate either as there's simply no reason to require it.

24 Hz output exists on newer Blu-ray and HD DVD sources to eliminate the motion judder that occurs as the '3:2 pull-down' process no longer needs to be used. 3:2 pulldown is the process of converting 24 frames/second film to 60 frames/second video required by most displays. Some newer digital displays (and video scalers) can accept the native 24 frames/second data thus eliminating 3:2 pulldown and the resulting judder effect noticed by some people. 3:2 pulldown judder appears as an uneven skipping of the image, most apparent during smooth pans in movies.

This judder shouldn't be confused with the general effect of fast pans appearing blurry due to film only being shot at 24 frames/second. Motion blur in fast pans in film is normal. Nothing can be done until studios start shooting at faster frame rates like 60 frames/second and a new disc formats are created to support this. This is not likely to happen any time soon. One reason being that people are used to the 'look' of 24 frames/second film and using higher refresh rates results in something that just doesn't look like film anymore to most people.

If you wish to use 24 Hz with a CRT projector in order to eliminate 3:2 pulldown judder, you will need to use a scaler to double or triple the refresh rate to at least 48Hz or 72Hz before feeding it to the projector. By multiplying the refresh rate evenly, judder is not introduced. DVDO, Lumagen, and others make scalers to do this. However, $1000-2000 to only eliminate 3:2 pulldown judder is more than most people are willing to spend, given that most people do not see or are bothered by this judder (we aren't). It is important to mention that 99%+ of televisions and projectors out there are run at 60Hz which requires the use of this 3:2 pull-down to translate 24Hz into 60Hz and it really has not bothered most people for the last 50+ years.

If you are not bothered by this judder or did not realize why 24Hz output existed then I would simply recommend that you not worry about it and run the Blu-ray player at 1080p/60! Simple, and no scaler needed.

There have been numerous topics on 3:2 pulldown and 24Hz output in our forum over the years. If you'd like to learn more feel free to search and read and ask further questions.

Kal

[kal]

HOME THEATER QUESTIONS & ANSWERS

Sign up for our newsletter and receive Home Theater Questions & Answers right in your inbox! This question is from our March 31, 2008 newsletter.

________________________________

Q: What's 1080p/24? Is it possible on CRT projectors? Does the Moome Sony IFB-HD HDMI card support 1080p/24 directly from a Blu-ray player to the projector (Sony G90 in my case)?

A: HD DVD and Blu-ray films are stored in 1920x1080 resolution at 24 frames/second (or Hz), referred to as 1080p/24. Film is shot at 24 frames/second so this is the 'native' rate of film.

The Moome Sony IFB-HD HDMI card does permit you to use 1080p/24 direct from a Blu-ray player. See the user manual available in the IFB-HD FAQ thread in our forum. However, (and this is important) you cannot use 24Hz refresh rate on any CRT projector or analog display device as the refresh rate is simply too low and the flicker that results from only refreshing the image 24 times/second is unbearable to watch. Many analog displays and CRT projectors will not sync as low as 24Hz refresh rate either as there's simply no reason to require it.

24 Hz output exists on newer Blu-ray and HD DVD sources to eliminate the motion judder that occurs as the '3:2 pull-down' process no longer needs to be used. 3:2 pulldown is the process of converting 24 frames/second film to 60 frames/second video required by most displays. Some newer digital displays (and video scalers) can accept the native 24 frames/second data thus eliminating 3:2 pulldown and the resulting judder effect noticed by some people. 3:2 pulldown judder appears as an uneven skipping of the image, most apparent during smooth pans in movies.

This judder shouldn't be confused with the general effect of fast pans appearing blurry due to film only being shot at 24 frames/second. Motion blur in fast pans in film is normal. Nothing can be done until studios start shooting at faster frame rates like 60 frames/second and a new disc formats are created to support this. This is not likely to happen any time soon. One reason being that people are used to the 'look' of 24 frames/second film and using higher refresh rates results in something that just doesn't look like film anymore to most people.

If you wish to use 24 Hz with a CRT projector in order to eliminate 3:2 pulldown judder, you will need to use a scaler to double or triple the refresh rate to at least 48Hz or 72Hz before feeding it to the projector. By multiplying the refresh rate evenly, judder is not introduced. DVDO, Lumagen, and others make scalers to do this. However, $1000-2000 to only eliminate 3:2 pulldown judder is more than most people are willing to spend, given that most people do not see or are bothered by this judder (we aren't). It is important to mention that 99%+ of televisions and projectors out there are run at 60Hz which requires the use of this 3:2 pull-down to translate 24Hz into 60Hz and it really has not bothered most people for the last 50+ years.

If you are not bothered by this judder or did not realize why 24Hz output existed then I would simply recommend that you not worry about it and run the Blu-ray player at 1080p/60! Simple, and no scaler needed.

There have been numerous topics on 3:2 pulldown and 24Hz output in our forum over the years. If you'd like to learn more feel free to search and read and ask further questions.

Kal

[Person99]

Couple interesting things:
1) Film is shot at 24 fps but shown in theaters at 48 (most common) or (rarely) 72.
2) Many digital displays that except 1080p/24 convert it to 60. Those that don't generally display it at another rate (48, 72 or 96) just like you would do on a CRT.
3) Given that a CRT handles motion better than any digital, 60 Hz on a CRT can look better than a multiple of 24 on a digital. In fact to really notice the judder on a CRT at 60 Hz, you have to have just the right speed of pan.

[kal]

[kal]