Rendering shifts video, creating loss of sync.
by Joni Church
on
Apr 8, 2008 at 6:49:07 pm
I came upon a few similar issues in this forum and elsewhere on the net, but none that found a solution.
I'm working with 720p 23.98 footage in FCP 6.0.2, shot on a Varicam, and all is well until I render a clip. Whether the render is necessary due to an opacity change or a filter applied, as soon as a clip is rendered, it shifts and becomes out of sync with the audio. If I undo the render, it plays fine again. It's for a music video, so there's only one long audio clip which stays put. When I watch the cut using the Safe RT preview before rendering, everything matches up, but as I said, if I place the playhead anywhere on the clip and render, when the render finishes the video actually shifts in the Canvas. I should note that my render settings under the Sequence menu are all correct.
The footage was captured at 59.94 in order to run it through the DVCPRO HD Frame Rate Converter for slow motion purposes, and that process worked fine.
What I've tried so far (with no success):
1. Trashed all of my render files
2. Trashed my FCP prefs
3. Repaired permissions
4. Copied the clips into a new sequence in an entirely new project
5. Nested the 720p sequence into a 1080p sequence (a shot in the dark to see if forcing all the clips to be rendered would trick it into working)
6. Forcing the render by exporting a full-res Quicktime
10. Placing the clips in a 59.94 timeline and rendering (ridiculously grasping at straws, I know)
11. And of course, restarting after many of the above attempts.
Currently I'm running the original footage through Cinema Tools to convert it to 23.98 to see if that changes anything (instead of using the Frame Rate Converter), but I'm not very optimistic since the FRC has never given me any trouble before.
My profile specs aren't up to date. The current details are:
- FCP 6.0.2
- OSX 10.4.11
- Quad Core 2.5 GHz PowerPc G5
- 6.5 GB RAM
- Project file is on System Drive
- Render files are going to either a separate internal SATA drive (plenty of space free) or an external FW drive (tried both)
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 8, 2008 at 11:48:51 pm
It's true, it does seem like something easy is missing, which is why I wasn't worried about it at first. Now I'm not so sure.
When I render one clip on its own, it goes out of sync alone, the rest of the un-rendered clips are fine.
I'm working in DVCPro HD, and I did try resetting my Easy Setup, which didn't change anything.
Leaving the sequence un-rendered and exporting a QT doesn't help, because the force-render FCP applies before the export makes the clips go out of sync in the resulting QT file.
The abnormality in all of this is that it's only the clips that have a filter applied to them (any filter, doesn't matter which one) or an opacity shift that go out of sync when rendered. It's not like the whole timeline is out of sync, or the sync drifts. It's not even related to the audio at all, actually, that's just how I first noticed it. Even with no audio present, if I pull the opacity on a video-only clip down to 60% and render it, it shifts. It's puzzling.
I figure if I can't get to the bottom of this before I need to show my client the video, I'll have to figure out how many frames each clip shifts, and knock each of them out of sync manually before rendering so they line up once they're rendered... but I hate band-aids and prefer to find the source of the problem, (as I'm sure you do as well).
Thanks again for your input, it helps having another brain checking in on everything.
Re: Rendering shifts video, creating loss of sync. by Jeremy Garchow on Apr 9, 2008 at 12:46:50 am
[Joni Church]"When I render one clip on its own, it goes out of sync alone, the rest of the un-rendered clips are fine."
And if you remove all filters from all clips, it stays in sync (in a duplicated timeline of course)?
[Joni Church]"Leaving the sequence un-rendered and exporting a QT doesn't help, because the force-render FCP applies before the export makes the clips go out of sync in the resulting QT file. "
I fiugred as much, but worth it to check.
[Joni Church]"It's puzzling. "
No doubt.
Anyway you can post a small out of sync clip? If not, I understand. is the sync predictable? If you adjust opacity, then render, then adjust it again, the render again, is it the same amount of shift or is it different?
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 9, 2008 at 1:27:43 am
Yeah, they all stay in sync if the filters and opacity adjustments are removed.
I was also thinking when I got home tonight about whether or not the sync would shift the same amount after multiple adjustments and renders- I hadn't considered that before, so it's a good question. I'll do some tests tomorrow, and let you know what I come up with. I'll also post a clip when I get back into the suite.
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 14, 2008 at 2:27:32 pm
Hey Jeremy,
I'm sorry I dropped off the face of the earth- our server went down for a couple of days and then we moved offices so we just got back up and running today.
I did some more tests this morning, and after rendering it appears the actual timecode of the clip doesn't change. The video most definitely shifts to another point in the clip, but the timecode reads as if no change has been made. So the only way for me to bandage it is to guess how many frames the clip shifts, bump it out of sync by that many, render, and check it. Less than ideal, of course. I did find that it only shifts once after rendered, so if I adjust it, render, and adjust it and render again, it doesn't keep shifting (I hope that makes sense).
At this point I'm not sure where else to go with it. I think I might need to quit editing and open a flower shop. Flowers never need to be rendered.
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 14, 2008 at 3:15:41 pm
No, it wasn't updated at all so that's not an issue. I actually sent the deck I rented (Panasonic 1400A) back last week, so I'm going to try to get another one in this week and recapture a few clips to see if it helps. It's our only hope!
Re: Rendering shifts video, creating loss of sync. by Jeremy Garchow on Apr 15, 2008 at 4:19:45 am
[Joni Church]"It's our only hope! "
Yep. As far as I know (which doesn't go that far), and without being there to see exactly what is going on, it's hard to determine what is happenin. A recap will help reveal or solve the problem.
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 15, 2008 at 6:32:28 pm
Since I can't get a deck until next week, I figured I'd try a few new ideas (credited to my co-worker as well).
He wondered if exporting a full-res Quicktime of the original material captured at 59.94 and then bringing that file back in to FCP and re-running it through the FRC would do anything. It didn't.
However as a last ditch attempt, I exported the files (simple EXPORT> QUICKTIME MOVIE) that I had already run through the FRC to convert to 23.98, and reconnected the clips using that media, and it worked. No sync problems whatsoever. All is well in the world. I still can't explain technically why this would be (which still drives me crazy), but there it is. A solution.
I wanted to post it in case anybody else ever encounters this mess of a problem. Thanks again for your input!
Re: Rendering shifts video, creating loss of sync. by Joni Church on Apr 21, 2008 at 1:07:49 pm
That's what's so weird about it, I did run them through Cinema Tools to conform to 23.98 and it didn't help. When I first ran them through the FRC I conformed to 23.98.
Re: Rendering shifts video, creating loss of sync. by Stuart Lanceley on Apr 21, 2008 at 3:46:39 pm
I have had a similar-ish problem with certain shots in a sequence going out of sync with the audio when i export using 'Quicktime Conversion->H.264'
This was an interview shot on two HDV cameras, one was a wide shot, the other handheld closeups.
The video footage shot on the handheld camera was all about 16 frames out of sync with the audio after exporting.
This caused missed deadlines, diplomatic breakdown with client and much hair loss.
I found that if I made a duplicate sequence, changed the sequence Settings to 'None' compression and then exported using Quicktime Conversion-> H.264, then in the Video settings selected 'Key Frames -> All' that the problem was fixed.
I have no idea why. I just hope this saves someone else some brainache.
