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-   -   24p questions (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/34265-24p-questions.html)

William LiPera November 2nd, 2004 07:25 PM

24p dvd and HDTV
 
Will it play 24p without pulldown on a progressive scan dvd player playing on a widescreen hdtv with component input? Thanks. Just want to get this straight.

Barry Green November 2nd, 2004 08:31 PM

It is my understanding that it will, but I don't have that combination so I can't say for sure.

Joshua Starnes November 3rd, 2004 11:27 AM

Re: 24p dvd and HDTV
 
Will it play 24p without pulldown on a progressive scan dvd player playing on a widescreen hdtv with component input? Thanks. Just want to get this straight.

No, it won't, because there are no TVs that exist right now that will show a pure 24p image.

The TV will perform the pulldown in order to show a 24p image on a 30i screen (which is what all HDTVs are right now) and that is it.

There is no way to show a pure 24p image on a TV right now-it doesn't matter whether it is an HDTV, component input, progressive scan DVD player or not. You can see an approximation of it, but not the real thing.

One day there will be TVs that can show an actual 24p image, but they don't exist right now.

Marty Hudzik November 3rd, 2004 12:02 PM

I'm not trying to question you on this but I thought HDTV was progressive by nature? You know.....720P is one of the standards. Why would we be limited to interlaced. Also....there are televisions that are advertised as doing 3:2 puldown removal on the fly for better image quality. Why would it remove the 3:2 pulldown from the source file just to re-add it on the boob tube itself? It seems that adding this as a feature would be pointless if the display can't actually display the 24P image.

Anyone got some hard concrete facts on this? Because I always thought a progressive 24P dvd would play back at 24 FPS on a "qualified" HD monitor. Some may not but I think it is a feature that is available.

Joshua Starnes November 3rd, 2004 12:37 PM

They are progressive by nature, but they are progressive at 30p only (I realize now I mistyped in my previous answer). When the TV is reading the progressive DVD player, it is reading it at 30p, not 24p. However, that does not, to the naked eye, change the movement of something that originated in 24p.

There is no TV that will show a true 24p image at the moment.

Marty Hudzik November 3rd, 2004 12:56 PM

Well the whole thing seems rather stupid to me. Why advertise that your TV has 3:2 pulldown for higher image qulaity when it doesn't really do anything but add back the same extra frames/fields that it is supposedly removing?

On another note I read somewhere that it may actually show 60P instead. In other words the 3:2 puldown is not field based but just time based. IT would show the first frame for 3/60 of a second and the next for 2/60 and the repeat. So it is doing a 3:2 pulldown but shows each full progressive image the entire time. Make sense?

The 60P is based off of the 60hz of US power supply. I also read that if we could generate a 72HZ signal to refresh the monitor then rather than a 3:2 pulldown it could do a 3:3 puldown....if that is the right term. In that case it could show each progressive frame 3 times and then move onto the next for 3 and so on. Then every frame would be even, temporally speeking, and fit exactly 24 in each second. This is not that different from how movie houses actually show each frame twice. The eye can't perceive it and we just see an even, non juddering cadence.

William LiPera November 4th, 2004 10:50 AM

24p for dvd
 
Is there any real advantage to editing in 24p (rather than 2:3 pulldown 60i ) if the final product is dvd in a progressive scan dvd player for hdtv widescreen viewing. As far as I understand progressive scan dvd players output 30p after de-interlacing the footage.

Christopher Go November 4th, 2004 11:53 AM

ISO Rating for XL2 in 24P?
 
What is the XL2's ISO rating at 24P, 16:9, with 1/48 shutter?

Joshua Starnes November 4th, 2004 12:18 PM

Yes. It will enable your cuts to be more accurate. Also it will allow you to follow the timecode you recorded. It will also make a major difference on you sound editing.

Stay in 24p until its time to put it on a DVD. That will give you the best results.

Yi Fong Yu November 4th, 2004 01:35 PM

what's iso?

David Lach November 4th, 2004 01:48 PM

ISO is the film stock sensibility, formerly known as ASA. The equivalent in video is EI (exposure index).

I was planing to test every setting this week-end (every gain level).

I might post my results if nobody has done it yet.

Pretty simple to test, you shoot a flat lit 18% grey card in auto mode with the gain level of your choice, and find an ISO setting on your meter that will match the aperture chosen by the camera with the corresponding shutter speed.

William LiPera November 4th, 2004 02:10 PM

24p to dvd
 
In what way will the cuts be more accurate and how is the sound affected if with 2:3 pull down no frames are lost ? This particular issue has never been clearly explained, from what I can find. Thanks

David Lach November 4th, 2004 02:56 PM

The two major advantages I see of editing in 24p (assuming you will shoot 24p regardless) is less rendering time and less compression on your DVD.

Less rendering because you only render 24fps instead of 30. If you've done complicated effects in post before, you know how much of a time saver this will be.

Less compression on the DVD based on the same principle. You only put 24fps on the DVD and let the DVD player do the 3:2 pull down when played on the TV. That way, you need to compress 6 less frames per second, meaning there's more room the preserve the overall quality (24fps compressed over 4.7GB or 9.6GB instead of 30fps).

William LiPera November 4th, 2004 03:16 PM

24p for dvd
 
But if your project is less than an hour, can't you fix the amount of compression to a low rate, regardless of the frame rate, to yield the same quality?

David Lach November 4th, 2004 03:43 PM

Sure you can, if you have enough room regardless, it's not really a problem, and won't make a huge difference.

You will still need to render only 24fps instead of 30fps, so you save time with your NLE rendering no matter the time of your project.


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