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TV to view 720/30p and 480/24p material


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#1 of 13 OFFLINE   ashley__cooper

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Posted September 06 2003 - 07:06 PM

I asked this in the HT basics area but no one responded.

I'm new to these forum and have read a lot of the basics, but am still confused. I'm an indie filmmaker (or video maker as I use video instead of film) and I was wondering if there's a decent sized TV that can display these images with out converting them. If anyone's interrested, I'm asking about this because 2 cameras recently came out that use these formats.
What I really want is a rear projection TV that can handle this kind of content. Plasma and LCD are just too pricey right now for me. Also curious about 480/30p material. So, is there a rear projection TV that can handle these formats without converting them?
Hate to drag this into the ground, but could someone also confirm to me that the "Reverse 3:2 Pulldown" and "Digital Reality Creation" features on some TVs doesn't mean it displays 24p without conversion

Thanks ahead of time for any information!

#2 of 13 OFFLINE   Allan Jayne

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Posted September 07 2003 - 03:30 AM

Are you sure the camera really outputs 720/30p, 480/24p, or 480/30p uncompressed? These are not standard consumer video formats and no ordinary or HDTV set can accept them.

As far as I know, video cameras only output standard video, making the conversion for you as needed. In order to convert the aforementioned camera frame rates to standard video, pulldown is used. THe 24 fps video camera or telecine machine creates the 3-2 pulldown so 60 fields or frames come out each second. (59.94 to be more exact for NTSC)

Meanwhile the TV also scans the picture tube only at certain standard top to bottom field (interlaced) or frame (progressive) rates namely 59.94 fps for progressive NTSC and 50.00 fps for progressive PAL. (If you use an external scaler, you can deal with other frame rates like 72, 75, or 100 fps that a TV might accept) I do not know of any TV that scans top to bottom a 720p or 480p picture 24 times a second and if it really did so, there would be a terribly annoying flicker in the form of a thick horizontal darkish bar rolling down.

A more correct description for "reverse 3-2 pulldown" is "3-2 pulldown recognition, optimizing, and preservation". The pulldown, when present in the source, needs to be preserved without weaving together non-matching interlaced fields when the video gets to the screen. The TV, doing HDTV or progressive scan, is still receiving 60 fields or frames (not all unique subject wise in the case of 24 or 30 fps film or camera material) via the input and putting 60 frames (fields for 1080i) on the screen every second (50 for PAL).

Video hints:
http://members.aol.c...ynejr/video.htm

(For HDTV transmission, film source video is often in such formats as 720/30p or 720/24p, but before sent to the TV, it must be MPEG decompressed and the 3-2 pulldown re-imposed.)
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#3 of 13 OFFLINE   Stephen Tu

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Posted September 07 2003 - 03:35 AM

No consumer TV will display at these rates; it's too low to avoid flicker. They all display at 60 frames (or fields) per second.

The "reverse 3:2" is just a way to cleanly convert 60i -> 24p -> 60p (60p is the final display rate) when the processor detects video originating from film.

#4 of 13 OFFLINE   ashley__cooper

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Posted September 07 2003 - 09:43 AM

Yes, I'm sure about these new formats. It's very exciting for would be filmmakers using video. The camera that shoots 480/24p is the Panasonic DVX-100. It can also shoot at 480/30p. It's a little conplecated how it works, but in 24p mode it adds interlaced frames which your editing software recognizes and removes- returning it to 24p. Don't confuse this with software conversion of 60i material into 24p- what the panasonic does is much different.

The other camera just released is the JVC HD10U. It shoots 720/30p material with MPEG2 compression and 480/30p w/o the mpeg compression.

I just tried giving a link to check out these cams, but the forum won't let me. Oh well.

My editing software allows me to make a dvd in 24p and my understanding was you could view it through a plasma or LCD screen. Is this not the case? I really thought you could at least watch 24p material through your computer LCD screen.
Sorry, guess I'm still confused as I think you both are saying that 720/30p and 480/30p material will also not be accepted by an HDTV. Thought these were okay for HDTV. Could you please clarify?
Thank you for your time and concern.

#5 of 13 OFFLINE   David Lorenzo

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Posted September 07 2003 - 10:10 AM

Ashley,

The camera does not output 480 24p or 30p. They are both converted to 480i.

The way that software performs 3:2 pulldown on a film based DVD is the exact same thing that must be done to reconstruct the 480i coming from the camera back into 24p or 30p. There's nothing special happening there.

What you want is a display that can do 480p and 720p. A RPTV based on the HD2 DLP chip would be good, but it would scale the 480 material up to 720p.

Good luck,
David

#6 of 13 OFFLINE   Tommy Haupfear

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Posted September 07 2003 - 10:41 AM

David made a good point about a DLP based RPTV. That way you have 720p support for that quirky JVC consumer HD cam.

I desperately wanted that cam to be the answer to my widescreen dilemma but other than higher resolution it doesn't offer much in control or color accuracy compared to today's top 3CC prosumer models.

I eventually just picked up Sony's PDX10 which gives me the a true 16:9 picture in a compact package.
Tommy Haupfear
Greenville SC

#7 of 13 OFFLINE   Stephen Tu

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Posted September 07 2003 - 11:13 AM

Quote:
Sorry, guess I'm still confused as I think you both are saying that 720/30p and 480/30p material will also not be accepted by an HDTV. Thought these were okay for HDTV. Could you please clarify

These are valid DTV transmission formats. The STBs will accept them. But the displays themselves generally don't sync to these rates; the STB has to convert them to 60p.

#8 of 13 OFFLINE   ashley__cooper

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Posted September 07 2003 - 11:20 AM

Thank you both. David, I'm not very good at explaining what happens with the PAnasonic dvx100, but my understanding is it shoots at 24p in two different modes and adds interlaced elements when output. The editing software, like Final Cut Pro or Vegas, then removes the marked interlaced elements and returns the material to its original 24p state. I may be wrong about this is a few ways, but I know it is very different from converting native 60i material into 24p.
More importantly though, I'm unfamiliar with the HD2 DLP. Is this new? Are there disadvantages of converting 480p material into 720 as far as accuracy for filmmaking? Can you recommend any models?
Thanks for all the help!

#9 of 13 OFFLINE   Allan Jayne

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Posted September 08 2003 - 06:20 AM

IMHO, if the camera delivers the video as 480i or 480p, you are better off editing it as 480i or 480p, preferably 480p if you have a good de-interlacer between the camera and the editing machine. If you edit and store the video as 720p it takes up a lot more disk space but the resolution of the subject matter is still 480p quality.

To save more disk space, editing is better done using the video as 24 fps, without the 3-2 pulldown. If the camera outputs 480i, what must happen is this:

1. A de-interlacer, either stand alone or in the editing machine or in the editing software, converts the 480i to 480p 60 fps. A top quality de-interlacer without 3-2 pulldown sensing and optmizing will yield video that pretty much has the 3-2 pulldown preserved, given 24 fps film source, although there may be minor frame to frame discrepancies.

2. The editing machine also looks for 3-2 pulldown, keeping one frame from each threesome and one frame from each twosome which yields true 480p 24 fps video. (if the incoming video was not 24 fps film, the editing machine needs an alternate strategy which I won't discuss yet.)

3. You do your editing.

4. You would save the master copy digitally as 24 fps but to make VCR tapes your editing machine must regenerate 3-2 pulldown for standard 480i 30 fps. A DVD burner may accept 24 fps video but then it too might require the 480i.

5. You can make 720p copies of the finished video from your 480p master.
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#10 of 13 OFFLINE   ashley__cooper

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Posted September 08 2003 - 09:17 AM

I wish I could post where to check out these cameras, but they won't let me. but check out the models i mentioned at panasonic and jvc for more info. sonic foundry (who just got bought by sony) makes vegas+dvd editing software specially designed for editing the panasonic 24p camera and making 24p dvds.
Here's what someone wrote on a vegas forum about 24p viewing:

"all new panasonic HD plasma's can play 24p at 24fps ..
sony has a few HD plasma's that can at 24fps and will include it on new HD plasma models as they are introduced.

a few sony's HD TV's can do a reverse 3:2 pull down from source material to play 24fps ..

many digital projector's can play 24fps.. many hi end DVD players can remove the 3:2 if source was 24p and on DVD at 29.97.. "

He seems to be disagreeing with what was said here about HDTVs only being able to show 60i or 60p material and the reverse 3-2 pull down. Is he right, sort or right, or just plain misguided?
Thanks again for any help.

#11 of 13 OFFLINE   David Lorenzo

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Posted September 08 2003 - 05:10 PM

Ashley,

Any HD display will show 480p.

I don't understand your question about 24p. You want the display to show it at 24hz? What's the point? If it is shown at 60hz the only thing that happens is the frames get repeated 2 or 3 times.

If a digital projector displayed 24p at 24hz there would be noticeable flicker and would probably be very distracting. The only projector I know of that doesn't convert 24p into 60p is the InFocus 5700 and the upcoming 7205. These display 24p at 48hz, showing each frame twice. I don't know of any plasma that will show 24p at 24hz. Maybe if you fed it with a PC at a custom resolution and refresh rate it could.

#12 of 13 OFFLINE   Stephen Tu

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Posted September 09 2003 - 07:42 AM

Quote:
He seems to be disagreeing with what was said here about HDTVs only being able to show 60i or 60p material and the reverse 3-2 pull down. Is he right, sort or right, or just plain misguided

The guy's half right. The deinterlacers in the DVD players / TVs detect the 3-2 pulldown on the 60i material and convert it internally back to 24p. But they then take those frames and repeat them to get to 60p (or 48/72/120 with the right processor/PC & compatible projector). They never actually display at 24p because of the flicker that would result.

#13 of 13 OFFLINE   ashley__cooper

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Posted September 09 2003 - 07:17 PM

I just asked that guy if he was sure about the 24p on HDTV and here's what he said:

"i am 100% positive -- as I extensivly use hdtv format and higher and use plasma's and hdtv tv 's and monitors and a number of video projectors to test with -- about 15 of such within 50feet of me right now in fact ..

I guess the people who told you that misinformation don'tgo to watch movies much in a theater- as films have the same 24 frame per sec flicker ..

in our company , we most often use a higher frame rate for most of our films .. but standard filsm are 24fps ..."

Then someone else expanded:

"When you watch a movie in a theater, you are seeing 48 images per second.

This is because each film frame is shown twice (using a rotating two-bladed shutter) before moving on to the next frame, in order to reduce the flicker.

But to avoid confusion let's spell out that you're seeing 24 distinct images per second, flashed 48 times per second. They flash the visible image twice, to help smooth out the dark period when the film is moving to the next frame."

My only goal is to watch my 24p material as it would look in a theater. Does this mean I need 24p at 48hz? Is there an HDTV or projector that someone can recommend that will do that?





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