Sync drift problem with long (3min+) shots - please help!

[GigaSnow85]

Hi All

My Set Up:
1.) 4k .r3d file into RedRushes, transcoded into 1/4 res ProRes 422 HQ .mov.
2.) Imported into FCP, on a 24fps timebase, with 48khz/24bit 24fps broadcast .wav audio file, synced up to boards using in points.

The Norm:
Works fine.

Until...
I have a long continuous shot, ~ 3 minutes +, which due to its size is automatically partitioned into _001, _002, _003 etc. .r3d files.

Opening the _001 .r3d file upon playback OR processing opens the whole file, i.e. all partitions.

The same with RedRushes - it takes the (for example) three partitioned .r3d files and outputs one .mov.

But...

Once in FCP, synced up to the sound using boards/in points, after a minute or two into the one long take, the sync starts to drift.

A colleague of mine was only dealing with a one-off long shot, so he simply nudged the sync back in when the actors weren't talking.

My problem is that I'm dealing with a lot of long takes, so I'm wondering if this curious conundrum is a problem within RedRushes and its processing of the partitioned .r3d files.

Or is it something else?

If it is RedRushes - any quick fixes that can be applied?

Any help would be much appreciated.

Cheers!

 

[Priit Poldmaa]

I don't know is it the same but we have found some oddies with sound.

We extract sound with QuicTime Pro via proxies to wav files.
Picture is rendered out to DPX or TGA using RedCine.
Both on PC.
All clips have audio one or tow frames longer than picture.

It seems to me that Red One does record bit more audio than picture.

Priit

 

[Scott Mason]

I don't know if this helps, but we had the same problem in a telecine session once and it was because the nagra did not have house sync running to it. I bring this up because it is very possible it is a drop frame issue that is causing this. If short takes work fine and long takes do not then most likely the video and sound are not running at the same rate. make sure they are both 23.976 and/or 29.97 or 24 and/or 30. It does not matter if the video is 23.976 and the sound is 29.97 so long as they are both drop frame (indicated by the .something). What can cause problems is a 24fps video and a 29.97 sound or a 23.976 video and a 30fps sound. You see a second is always a second so frame rate will not change the sync of sound, but dropping or not dropping frames will. good luck.

 

[GigaSnow85]

Thanks for the suggestions

I should have made clear that I receive sound on a separate flash card, so I don't have to extract sound etc.

Also, everything is on a 24fps timebase.

Any other thoughts?

Cheers!

 

[Stuart English]

Sound Sync

Sound Sync

Also, everything is on a 24fps time base.

Can you 100% verify that you did not record video at 23.98 and sound at 24.00 or vice versa ?

On the "drop frame" comment, its the other way round - make sure that you record NON Drop Frame on both devices, RED-ONE only supports NDF.

 

[MichaelP]

A 23.976 versus 24 issue would manifest itself as a 1 frame cumulative out of sync every ~40 seconds.

Michael

 

[Cail Young]

My problem is that I'm dealing with a lot of long takes, so I'm wondering if this curious conundrum is a problem within RedRushes and its processing of the partitioned .r3d files.

Or is it something else?

It's something else. Final Cut Pro cannot handle 24.00fps BWF audio correctly (at least in my experience).

If you can track down Sebsky Tools (I have a copy if you'd like it) it will convert the BWF to a .mov so you can still sync with timecode.

I've heard a suggestion that the capture settings might fix the issue but it needs to be changed before you import any BWF files.

 

[Bal Deo]

A 23.976 versus 24 issue would manifest itself as a 1 frame cumulative out of sync every ~40 seconds.

Michael

as micheal mentioned this may be the cause. We fell in to this trap. To do a quick test, take a single clip and convert it to 23.976 using cinema tools and try sync. Ensure you duplicate the clip before converting as a safety measure.