Urgent QT sync problem - is it my fault?

[idris]

Scenario :

- feature film supplied in 6 reels as MPEGs
- picture resolution too low to spot footsteps etc reliably.
- converted to QT with MPEGStreamclip
- source and destination files 24fps

- feature also supplied as PAL DVD (the type you rent from Blockbuster. Is there a technical term for these?)
- picture quality is still "off line" but better than the MPEGs
- DVD has the film split into 4 VOB files.
- DVD ripped and converted to QT with MPEGStreamclip
- QT DV Pal codec set to 24 fps

In the Session Setup window
- Timecode rate = 24fps
- Frame + feet rate = 24fps
- No pull up/down for video or audio


Theory suggests the files should match up like this

/--- MPEG R1 ---/--- MPEG R2 ---/--- MPEG R3 ---/--- MPEG R4 ---/--- MPEG R5 ---/--- MPEG R6 ---/
/------- VOB R1 --------/------- VOB R2 --------/------- VOB R3 --------/------- VOB R4 --------/

Spot checking 10-15 picture cuts every few minutes I've found the following :
MPEG R1 matches the 1st part of VOB R1
MPEG R2 (1st half) matches the 2nd part of VOB R1
MPEG R2 (2nd half) matches the 1st part of VOB R2 most of the time, but there are picture cuts that differ by 1 frame.


Replacement files are on their way, so that solves the probelem.
BUT, is this problem likely to have arisen because of the DVD autoring, the DVD/VOB to QT conversion, PT settings, or something else.

[Frank Kruse]

I always get dropped frames when ripping DVD video with MPEG streamclip. Ask for MJPEG or DV codec. avoid mpeg2. Delivering a reference video as DVD-VIDEO is high risk and not very professional. Ask for propper QTs instead of going through hours of conversion every time.

frank.

[sunsinger]

Same as above, after having alot of problems working on some Nat Geo programs, I started to have them deliver my videos
as Beta SP, and when I get those, I have a local video house convert my quicktimes into whatever I need... Flawless method, highest resolution...

[idris]

I always get dropped frames when ripping DVD video with MPEG streamclip.

Are the dropped frames cumulative or do they recover?
ie does the picture get one frame out, then two, then three, or does it recover to zero frames out and then go again some time later? (My problem is the latter.)

[mfranken]

The QTs that are converted from the PAL DVDs will be out-of-sync by up to a frame (strictly speaking 1/2 a frame). This is because the DVD has repeated fields (1/2 frames) twice a second to spread the 24 frames of the original footage over the 25 frames required for PAL. So when you capture the 25FPS into a 24FPS QT, the frames as such in the QT will not be the same as if it was generated from the original 24FPS footage.

If you want a true 24FPS QT you'll need to get the offline to create that for you inside the AVID/FCP. If they transfer to PAL digibeta/beta (any PAL device) you'll still get this frame/field inaccuracy.

I've never tried converting DVDs to QTs, so I'm not sure if this may be dropping frames as well. To check this, go to the 0 frame of any second and compare your pictures. I'd just check the start and end of each reel. The above problem should only appear within the second.

Regards,

Mark