Progressive DVD Export from HDV

[David Newman]

Originally Posted by Bill Binder

For starters can't a DVD hold a 24p MPEG2 file?

No, the pulldown is rendered in so that a 24p source is encoded as 60i. There are no 24p encoded DVD, only 60i with 3:2 pulldown (or 25p within 50i.)

[Bill Binder]

Originally Posted by David Newman

No, the pulldown is rendered in so that a 24p source is encoded as 60i. There are no 24p encoded DVD, only 60i with 3:2 pulldown (or 25p within 50i.)

I actually think you might be wrong on that one. 23.976 fps is part of the MPEG2 specs, and to my knowledge many commercial DVD's come as true 24p on the DVD, then the DVD player inserts pulldown only if needed (on a TV that can handle 480p it won't bother). That's not to say much 24p footage is encoded to 60i with pulldown already inserted, and then some DVD players (or the TV can do it too if it is modern), can REMOVE the pulldown to display a 480p version at 23.976 fps. My understanding is that it can go either way, because people can and do squeeze more time onto true 24p DVD's (at the same bit rate) than they can for 60i DVDs.

In the case of 24 fps source, the encoder embeds MPEG-2 repeat_first_field flags into the video stream to make the decoder either perform 2-3 pulldown for 60Hz NTSC displays (actually 59.94Hz) or 2-2 pulldown (with resulting 4% speedup) for 50Hz PAL/SECAM displays. In other words, the player doesn't "know" what the encoded rate is, it simply follows the MPEG-2 encoder's instructions to produce the predetermined display rate of 25 fps or 29.97 fps.

Here's a link:
http://www.dvfilm.com/maker/24Pdvd.htm

And a google search:
http://www.google.com/search?q=24p+dvd+mpeg2

[David Newman]

Sorry, I do know this one. The MPEG2 does has progressive modes, yet these are not support in today's DVDs. Pick a copy of DVD Demystified. 24p is encoding as 60i with repeat flags.

[Daniel Rudd]

so should I bother with a progressive DVD?

[David Newman]

Absolutely, it is the best look for progressive HDV content.

[Daniel Rudd]

I'm not being argumentative. I'm sincerely trying to understand.
If it's just 60i with repeat flags- how does it alter the image.

Daniel

[David Newman]

Yes it is confusing. An interlace storage system like DVD doesn't care whether you encode 60i unique fields or 24p via 3-2 pulldown, the disk still sees 60i (all interlaced coding is used.) Yet a progressive scan DVD player can see these repeat flags and reconstruct the progressive image, perfect for upscaling to an HD display. This is why it is worth it.