I need help with a 30p DVD at DVinfo.net

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Old December 1st, 2009, 07:51 PM   #1
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I need help with a 30p DVD

I am having some trouble putting a 30p project on DVD. Hopefully someone can help me.

As far as I know (and someone correct me if I am wrong), the average DVD player will take the 30p content on the disc and pass it along to the TV as a 60i stream. Then, the TV is supposed to recognize that the 60i stream originated as 30p, reconstruct the original frames from adjacent fields, and then play each frame twice to achieve its native 60p playback.

However, I have tested my 30p DVD on two different DVD players, and two different HDTVs, and the 60i stream coming from the DVD player is NOT being handled correctly. Instead of recreating the original progressive frames, the TV is performing its own 60i-to-60p conversion (i.e., using each field to create its own full frame), and this results in a flickering mess.

I have no idea where the problem lies. Do I need a special DVD player and/or TV to correctly play a 30p DVD? That would seem strange considering that all Hollywood DVDs are 24p and seem to work fine. I realize there are progressive scan DVD players, but it was my understanding that even normal DVD players should recognize and pass along a progressive flag to the TV, so that the TV can correctly reassemble the original frames.

Or is the problem in the DVD itself? I know for a fact the m2v files created by Compressor are indeed 30p. Could it be that DVDSP is not flagging the video as truly progressive? How can I be sure?

Please help!

Thanks,

Mike

Any help would be much appreciated.
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Old December 1st, 2009, 08:57 PM   #2
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30P is not within DVD spec, only 60i and 24P, you need to change your project to 60i before you encode to MPEG2.
You are confusing frame rate 29.97/sec which is 59.94 interlaced, that is not 30P.
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Old December 1st, 2009, 10:16 PM   #3
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My 29.97p (lets just call it 30p) mpeg2 files were successully burned to DVD, and I know for a fact they were not re-encoded by the authoring program. And I do know the difference between 30 full frames per second and 60 interlaced fields per second.

So, 30p is indeed allowed for DVD. The question is, why can't a HDTV play them back correctly? Afterall, it plays back 24p correctly. In both cases, the DVD player is passing along the video at 60i.

Is it just that HDTVs are designed to detect 24p sources in a 60i stream, but NOT designed to find 30p sources in a 60i stream?

Thanks for your help.
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Old December 2nd, 2009, 01:51 AM   #4
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Well, after some more tests and some more forum browsing, i think i may have found someone with the answer. This is quoted from a user on a different forum:



"Of course 30p can be encoded as 60i, however interlace presentation has flicker issues if the source vertical bandwidth is too high. 30p to 60i can cause twittering (inter-line flicker) when a display converts 60i to 60p for HD display (most displays aren't expecting 30p over 60i sources, so they do the interpolation wrong.) ... Bascially most modern display can do 2-3 pulldown reconstruction, but not all do 2-2 (30p in 60i) pulldown detection, mainly because 2-2 sources are rare in professional sources.

DVD -- doesn't have either 24p or 30p profiles, only 60i, but all progressive DVD player can remove 2-3 pulldown, but not all 2-2, so same issues as BluRay. So 24p looks go on progressive displays, yet the 30p experience is varied. CRT display is fine for both, its the move to 60p progressive displays that is the issue.

Note: 24p on DVD/BluRay, pulldown is added automatically by the authoring sotware, you don't want to add pulldown manually with After Effects or elsewhere as the authoring software will like encode the image as regular 60i source (20% less efficient = lower quality) and not set the repeat flags -- many progressive DVD players use the repeat flags to extract pulldown. 30p on DVD has no repeat flags, making progressive detection more difficult."



It seems most HDTVs do not correctly detect a 30p source in a 60i stream, resulting in the flickering I was seeing.

Thanks for responding.
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Old December 9th, 2009, 07:27 PM   #5
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Quote:
Originally Posted by Mike Dominic View Post
My 29.97p (lets just call it 30p) mpeg2 files were successully burned to DVD, and I know for a fact they were not re-encoded by the authoring program. [snip] So, 30p is indeed allowed for DVD.
You can burn anything to a DVD, it is just a disc with a file system. That does not make it allowed by the DVD video specs.
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