[x liddy x]

Hey.

I'm considering buying an optoma HD65, but this question has been going through my mind.
If this is a native 720p projector, what advantage do i get from using 1080p/24 with Blu-ray?
What does 1080p/24 actually do?

[alchemistkevin]

I could either type it in my words or just provide the following links


HDTV UK

An AVF Discussion thread here

[Jonstone]

The importance of 1080p24 is in how the film is encoded on the disk in the first place.

Blu ray movies are encoded at approximately 24 frames per second. If you have a display that can accept 1080p24 and produce the resultant image at a refresh rate that is a multiple of 24 i.e. 48 or 72 hz then you will get smooth playback.

If a display cannot do this then you will be introducing 3:2 pulldown judder.

Obviously if you take a source at 24 fps and try to display it at 60 fps like most displays do there has to be some conversion to get 24 into 60. This is generally done by repeating frames but in an uneven manner, some frames are repeated 3 times, others only twice ( hence the term 3:2 pulldown).

The result is a slight judder to the image which some people notice more than others.

Some displays will accept a 1080p24 source but still refresh at 60 hz so they still have judder, so the only way to make full use of 1080p24 is have a display that accepts the source and displays it properly.

Whether the HD65 does this I do not know but I am sure others can advise.

My projector for instance does not claim 1080p24 compatibility but I have found that although it won't take a 1080p60 source it will accept a 1080P24 one and with seemingly no judder and the difference is very noticeable

[x liddy x]

I understand what it is, i just don't understand what effect it would have on a 720p projector.

[Jonstone]

Exactly the same as on a 1080p one if it handles the source properly, it will be downscaled yes but it won't judder. It is definitely a feature I would recommend, if you notice judder it will definitely get on your nerves after a time

[Avi]

Originally Posted by x liddy x

What does 1080p/24 actually do?

Most "film" material is captured at a rate of 24 progressive frames (think of them as still images) per seconds. Ignoring the 1080 resolution bit it simply means the player can output film material at a frequencey 24 frames per seconds. Some displays will accept a 1080p/24 signal even if its native res is less than 1080 and still repeat the frames at a multiple of 24 thus eliminating the need for 3:2.

AVI

[alchemistkevin]

Some more info here

[x liddy x]

Ahh thank you.
So it's just because the films natural FPS is 24.
Thanks.

[Jeff]

It will make a film look like a PAL film rather than an NTSC film (in motion terms). PAL doesn't have 3:2 judder. So it's easy to know what 24Hz will look like in terms of motion smoothness, just watch a regular UK DVD.

[pjclark1]

My Toshiba EP-30 can play movies at 720p or 1080/24

On my hd-65
if I select 720p the output is at 50Hz
if I select 1080 the output is at 24Hz

As the film is encoded at 24fps it gives a smoother picture on 1080/24
Whichever way you play it a scaler will be used, so why not use the pj scaler and have the right fps?

[Avi]

Originally Posted by pjclark1

My Toshiba EP-30 can play movies at 720p or 1080/24

On my hd-65
if I select 720p the output is at 50Hz
if I select 1080 the output is at 24Hz

As the film is encoded at 24fps it gives a smoother picture on 1080/24
Whichever way you play it a scaler will be used, so why not use the pj scaler and have the right fps?

Do you mean movies on HD DVD or DVD ?

Unlike film encoded on HD DVD (or Blu-ray) R2 PAL DVD undergoes a speed up during the telecine process (not in the player) and should not be output at 24hz. R2 PAL DVD should be output at 50hz and HD DVD output at 24hz if the display properly supports it or 60hz (not 50hz) if it doesn't.

AVI

[Marky1973]

does the hd65 support 1080p/24?

[alchemistkevin]

Originally Posted by Marky1973

does the hd65 support 1080p/24?

according to the specs, yes