Interlace artifacts in 24pa encoded with iDVD

[KevinScott]

Hi all,

This is my first post, although I've benefited *greatly* from all the Q&A's, especially from Capt. Mench, Slapdragon, DVXShooter, Scottdvx100... thanks to you all.

I've just completed my first two short films, one entered in the 48HourFilmFestival, the other in the National Film Challenge; both were great fun & I learned a lot. All teams had one weekend to create & deliver their films.

I shot the NFC project in 24pa, edited in a 29.97 FCP-HD timeline...planning to deliver on DVD. I thought this would work fine (leaving the pulldown -in, and editing in a 29.97 timeline... since I knew I'd be outputting to DVD anyway), but after using Apple's iDVD to create the disc, I was majorly bummed when I saw interlace artifacts (odd/even scan lines) in our movie.

After doing some research (see thank you in 1st paragraph), I find that the DVX100a's progressive modes record to tape using interlaced fields to create a "progressive" frame... so the interlace'd fields issue will always be there to deal with. I kick myself now after realizing that NTSC can only record "one way", even though dvd players support progressive frame playback from a real 24fps disc.

At this point I've got a finished 24fps-movie (i.e. -shot in 24pa without removing the pulldown, with 8 audio tracks & 3 video tracks) sitting
in a 29.97 timeline.

Is it possible to remove the pulldown (from my current 29.97 timeline) and retain my edit?

If not, how can I keep the project intact and output a clean dvd without the interlace artifacts being so visible?

When using iDVD (because it's all I've had time to learn), the interlace artifacts are very visible and disturbing in scenes with motion... but... I recently purchased DVDSP (but don't know how to use it yet) and stumbled through the program well enough to have created a disc that does NOT exhibit the problem. Dumb luck?

What is DVDSP doing *for me, automatically*...that iDVD did not do... to eliminate the interlace problem?

Thanks from the newbie, but learning fast!

Photonic

 

[angrymexican]

Re: Interlace artifacts in 24pa encoded with iDVD

idvd does not support 24p DVD. You need to use DVD studio Pro.

 

[Scottdvx100]

Re: Interlace artifacts in 24pa encoded with iDVD

If you shot 24pA you shouldn't be seeing any interlacing, just duplicate frames. Note that 24pa will be slightly jerkier in a 29.97 timeline.
Try stepping through frame by frame on the computer.

If you want to go 29.97 timeline shoot 24p mode. This will have interlacing (just like a film that's transferred to video has interlacing) but the interlacing should look smooth on real video (not computer)

As mentioned iDVD doesn't support 24fps DVD. DVD Pro shouldn't really make a difference in your case unless you start with a 23.98 timeline. Then it's smart enough to do the right thing but it shouldn't be auto removing telecine interlacing.

 

[KevinScott]

Re: Interlace artifacts in 24pa encoded with iDVD

Thanks for your replies; perhaps I need to make it more clear that when I stated that I successfully used iDVD to create a disc, it was from my *existing 29.97 timeline*...I didn't remove the pulldown (B4 editing) & set up my edit using a 29.97 timeline, planning on outputting to a dvd disc. I know that iDVD doesn't support 24fps projects.

I absolutely shot 24pa, but even in FCP's Canvas & Browser windows I can clearly see interlacing in some frames... it now seems clear that it's due to the way the DVX100 records "progressive" frames to tape - it still records two seperate fields (odd/even), they just happen to be exactly the same, and when combined, produce one 'progressive' frame; ...and (in the 24pa mode) follow this recording pattern:  2:3:3:2   ...meaning 2 identical *frames* each composed of 2 identical fields, then 3 identical frames each composed of 2 identical fields, etc. 24pa uses this pattern:  aa:bb:bc:cc:dd, and then removing the pulldown discards the BC frames, if my understanding is correct.

My point is the fields are still there in a 29.97 timeline, and may cause a problem in the edit under certain circumstances.

My question is, since I'm working with 24pa footage captured straight from the camera (leaving the pulldown *in*) and editing this footage in a 29.97 timeline, why do I clearly see interlacing effects on some frames (i.e. action) when the disc is made using iDVD, but *not* seen if the disc is made using DVDSP?

Is it due to making an edit on a split frame that contains a field from two different 24pa frames, and DVDSP recognizes the split frames & is discarding them for me?

Does FCP's Browser or Canvas window show *both* fields, or only one field?

Since the edit has been finished and is in a 29.97 timeline, is it possible to remove the pulldown now without my edit getting hosed?

BTW, I shot 24pa with the possiblity of a filmout in mind.

Thanks for your help!