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Old March 5th, 2008, 11:58 AM   #1
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24p m2t conversion nightmare

I convinced an LA production company to shoot on my camera instead of a HVX200 P2, by offering to give them DVCPRO-HD 720/24p clips on a drive.
Rental income, more comfort with my camera, the extra work seemed worth it.

I'd done this before with a smaller batch of shorter clips no problem. I did some quick tests this time to confirm, and put them in a timeline with P2 footage I had from another shoot. Played back fine, looked great.

DVHScap to Mpeg streamclip (1.9 most recent version), 23.98fps, no interlace preset. Always repaired TC breaks.
This time it's 13 hours of footage (mostly long interviews). I found running over some breaks in shooting while making clips in MPGSC (Mpeg streamclip) knocked out sync, and I was able to go back and make new clips at these points, which always coincided with a pause in recording. A hassle, but this seemed to take care of it. I kept clips to under 20 mins even if I rolled interviews longer.

Everything looked good, but it was a rush to put it all together for the director to fly back with the drive. But, now, it turns out that I didn't notice that many clips lapsed into 12fps playback (actually 2 identical frames, skipping one frame). Not good. It's on me to fix it. I do see reports of this issue before, but no real solution. Just try again on that section and hope for the best...
The lapse into this skipped frame playback seems to happen randomly in the middle of clips unrelated to a camera pause. In interviews it's also hard to catch without careful review since there isn't that much movement.

HDVxDV I haven't tried, but it doesn't seem to have been updated recently, and sync problems with that sound nightmarish with 24p footage.

Hope someone can offer an approach to more reliable conversion.
Unfortunately all my m2t files are also on that drive in LA, and I just have a sample of one of the bad clips here. The client wants me to do the whole thing over from the tapes, which would be a real burden, and without a rock solid output. If it's using these tools, I think I'll want to be working through the existing drive, methodically re-doing the problem areas.

**UPDATE* I reached out via email to Andrew Young after searching the forums, and finding he'd done extensive work and reporting of issues with this process. He called me up 10 minutes later! I've got some solid other approaches to try - like transcoding from FCP captures with media manager.

Still up for comments and input though as I struggle with this.
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Old March 5th, 2008, 08:56 PM   #2
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Unfortunately I have no advice for you on your hardware/software, but I have had no problems transcoding from 24fps m2t's to 24fps dvcpro100 via canopus procoder.
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Old March 6th, 2008, 09:55 AM   #3
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Thanks Adam,
Pre-roll isn't really an issue here, (with settings to limit it to 1 sec), and I don't have a problem with clips getting broken up in the middle of a camera roll, so I'm capturing with FCP and converting with the media manager, which preserves timecode, and seems to be flawless so far. Should have worked this way from the start - it makes discrete clips by roll automatically and keeps TC (so editor can keep track of origins). I somehow thought of mpeg streamclip as having superior transcoding characteristics. It might be a bit faster, but that quirk was a real deal breaker. It seems this old workflow only makes sense if clip breakup and gaps are problematic with the tape (maybe from older camera) or system.
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Old March 6th, 2008, 03:02 PM   #4
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I agree with your findings, Sean. 100%.

From my own experiences, I've found:

1/ MPEG STREAMCLIP
Perfect for 25p.
Lousy for 24p (even when setting the Frame Rate at 23.976) with the same random "repeat frames" problem that you encountered. I would NEVER use it for 720p24 footage.

2/ HDVxDV
Gives a perfect conversion visually, so it's quite usable, but you get audio drift and have to be prepared to re-synch the audio to the actor's mouths in your FCP timeline. I only use it these days if someone gives me 24p footage shot with zero pre-roll and I find I really need those first frames.

3/ NATIVE CAPTURE IN FCP
For 24p footage, this is the way to go. Even if you get the occasional mid-clip break, it's still the way to go. No repeat frames and audio in perfect synch. From there, you can always transcode into a different codec, if you wish.
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