FORUMS: list search recent posts

Double system sound Sync issue

COW Forums : Apple Final Cut Pro Legacy

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Lars Fuchs
Double system sound Sync issue
on Dec 31, 2012 at 5:12:46 am

Dear Cow Experts!

I have a 71 minute interview shot on an HPX-170 at 23.98 fps 1080PA. I shot with a camera mounted Røde recording to the camera for reference and I used a Tascam DR-40 for double-system audio. It was recorded at 48 kHz. Synced using audio/visual clapper. wav files were converted to 24bit AIFFs in Compressor prior to importing to FCP. (Im using 7.0.3 on 2007 MBP w/4GB ram under OS X 10.7.5)

When I sync the audio to the picture using the clapper, the audio is in sync well enough for 10-20 minutes. Around then is when the slippage becomes noticeable. By around 58 minutes its about 8 frames off. The audio lags behind the video.

I wonder if anyone might have a diagnostic suggestion. I suspected it was related to pullup/down and just by experimenting I found that speeding the audio to 100.01% helped a lot. That makes the offset less than a frame.

That's not what I expected... I thought that the video, at 23.98 fps, was slower than real-time, implying that the realtime audio tracks should be slowed down to match. However, slowing the audio to 99.99% made it worse.

I have two questions -
1) Is there some pre-processing workflow I can apply to the double-system audio prior to import that will resolve the audio to the 23.98 video? What program(s) should I use?
2) Can anyone help me understand what's going on here?

Thanks
Lars


Return to posts index

Rafael Amador
Re: Double system sound Sync issue
on Dec 31, 2012 at 11:49:04 am

Hi Lars,
Duplicate the sequence and try to sync the original Wav files.
rafael

http://www.nagavideo.com


Return to posts index

Lars Fuchs
Re: Double system sound Sync issue
on Dec 31, 2012 at 7:46:10 pm

Didn't work.

I tried two things: creating a new sequence, dragging the video into it, and clicked 'yes' for FCP to match sequence settings to clip settings. Then I dragged the .wav file into the timeline with 'snap' on, which allowed me to align the markers i had placed at the clap. Same result as with aiff - starts okay, but by the end off by many frames.

2nd thing was to create a sequence from scratch and add the .wav as above, but with similar lack of sucess.

What else can I try?


Return to posts index


Lars Fuchs
Re: Double system sound Sync issue
on Dec 31, 2012 at 7:53:52 pm

I also created a prores sequence at 24 (not 23.98) and added the audio and video to that. Audio still lags behind video.


Return to posts index

Rafael Amador
Re: Double system sound Sync issue
on Jan 1, 2013 at 3:58:45 am

FC has a very well known bug that puts audio out of synk on certain circumstances.
Have a look to this:
http://library.creativecow.net/articles/lyon_matt/
rafael

http://www.nagavideo.com


Return to posts index

Lars Fuchs
Re: Double system sound Sync issue
on Jan 2, 2013 at 7:44:56 pm

I read Matt's article/tutorial. Here's what I've tried:

1) Set default sequence preset to 1920x1080 24p. Quit and relaunched FCP. Imported my video footage (DVCProHD 1080p30 23.98 fps, shot with HPX-170 at 1080PA24). Then I imported the AIFF (converted from .wav using Compressor). Synced to clapper, but same problem.

2) Set default sequence to DVCProHD 1080p24. Quit and relaunched FCP. Imported video footage, wav file. Synced to clapper, but same problem.

3) repeated above with default set to DVCProHD 1080p30. Quit & relaunched. Imported video and audio. WHen I put the video in the sequence, I did two ways, allowing FCP to match the sequence settings (making it 23.98) and not (forcing the 23.98 footage into a 29.97 sequence). Same problem, its out of sync noticeably an hour later. (It gets worse as time goes on but its perceptible around 20 minutes in).

4) I reset the default sequence preset back to Apple ProRes 1920x1080 24p, quit and relaunched, imported audio and video, forced the DVCProHD clip into the prores sequence (didn't allow fcp to match settings), then synchronized audio at the clapper. Then I exported an XML of the sequence and opened it in TextEdit. The video clip and the audio clip are both NTSC: TRUE and TIMEBASE 24.

So now I'm really up it, since Matt's fix seems not work. Have I missed something?


Return to posts index


Lars Fuchs
Re: Double system sound Sync issue
on Jan 2, 2013 at 8:35:18 pm

I have also tried to change the way the video clip is imported. So I opened Log&Transfer, and under preferences set P2-Plugin/P2 AVC-Intra to ProRes 422 (see grab:)



Unfortunately, it doesn't seem to make a difference. When I reimport the clip, its compressor is still DVCProHD 1080p30, frame rate 23.98. In the Log&Transfer window, I see that the source format and target format are the same regardless of the settings in the preference pane:



So now I'm really stumped.


Return to posts index

Todd Gillespie
Re: Double system sound Sync issue
on Jan 2, 2013 at 9:23:45 pm

Most of the time when this occurs, it's an issue with the original digitizing. Slow drives, full drives, or using the system while digitizing. Unfortunately once it's captured wrong there's no way to get the file to sync. You have to recapture . No redigitizing re-encoding will fix it.
Good luck
Todd

Todd at UCSB
Television Production


Return to posts index

Lars Fuchs
Re: Double system sound Sync issue
on Jan 2, 2013 at 9:55:04 pm

If I change the speed of the audio clip to %100.01, it stays in sync the whole way through. That suggests that it is a problem of 24 vs 23.98. Would mis-digitizing account for that?

[Todd Gillespie] "Slow drives, full drives, or using the system while digitizing."

I'm using a CalDigit VR external RAID 0 over FW800 importing from a G-Tech mini 7200 RPM. There's over a terabyte of free space on the CalDigit. I"m using a MBP 2.4 GHz Intel Core 2 Duo with 4 GB of RAM. I'm confident (but not 100% sure) that I left the system unattended during Log&Transfer). I can of course try it again, and I'l repost afterwards.

Interestingly, I installed a trial version of Premiere CS6, which will open the mxf files directly. Same problem!


Return to posts index


Lars Fuchs
Re: Double system sound Sync issue
on Jan 2, 2013 at 10:35:45 pm

As another test, I imported the audio into Audacity. There I sped it up by 0.01%. I also tried to change the sample rate to 48048Hz. I imported both back into FCP, and the first one worked very well, the second not. It was 4 seconds shorter than first (both were about 1hr 10min long). It didn't matter if the sequence was prores 1080p24 or DVCProHD 1080p24

go figure.


Return to posts index

Lars Fuchs
Re: Double system sound Sync issue
on Jan 3, 2013 at 12:44:31 am

So I downloaded SoundDevices WaveAgent app, and tried every combination of frame rate and sample rate and no luck. THE ONLY thing that works (so far) is to change the speed inside FCP to 100.01%.


Return to posts index

Rafael Amador
Re: Double system sound Sync issue
on Jan 3, 2013 at 4:22:28 pm

Lars,
Why are you working with REAL p24 sequences?
The PANAS do not make REAL p24.
Read here about DVCProHD 1080PA24.
http://documentation.apple.com/en/finalcutpro/professionalformatsandworkflo...
rafael

http://www.nagavideo.com


Return to posts index


Lars Fuchs
Re: Double system sound Sync issue
on Jan 3, 2013 at 5:36:53 pm

[Rafael Amador] "Why are you working with REAL p24 sequences?"

I'm not. I only created one as a test, to see if it made any difference. It didnt'. The editing sequences I hace have been using, and the default sequence preset, have always been 23.98. Please note that I had this problem even in a DVCProHD 23.98 Sequence (ie, camera-native.)

I will read the link you gave now.
-Lars


Return to posts index

Matt Lyon
Re: Double system sound Sync issue
on Jan 3, 2013 at 5:23:17 pm

Lars, the 100.1% speed change you are applying is consistent with the difference between 24.00/23.976 fps ... in other words, standard audio pulldown that is used for film workflows. As described in my tutorial, this is happening because something is preventing the audio from importing properly, and FCP is applying the incorrect NTSC flag. Look for the telltale orange bars I describe overlayed on your audio files...

If you're audio was being imported properly, the NTSC flag would be set to FALSE! So you need to revisit the steps you are taking when importing the audio, and figure out what is going wrong exactly. Your sequence preset should be set to a 23.98 frame rate. Try importing the files in a new, empty project and then dumping out a quick XML to verify the import worked.

I can't imagine that disk speed is an issue, since you are doing a completely file based workflow, no? There is no "digitizing" to speak of.

I don't have direct experience with the camera and audio recorder you mention, so I can't say whether something specific to those devices is creating issues too.

Hope this helps,

Matt Lyon
Editor
Toronto


Return to posts index

Lars Fuchs
Re: Double system sound Sync issue
on Jan 3, 2013 at 7:50:14 pm

I tried to follow your tutorial to the letter. However I AM in an NTSC region, so I don't want PAL sequences. With that in mind, here is a detailed explanation of the exact steps I've taken. (I wrote it down after each one, so I'm confident this is accurate.

Note, this is a long post with excruciating detail, so here's the bullet: it didn't work. I couldnt get them to be in sync.

Steps:
1) Downloaded Preference Manager
2) Backed up FCP preferences
3) Trashed FCP preferences (emptied Trash as instructed by PM)
4) Launched FCP.
5) Set new Default sequence as follows: DVCProHD 1080pA24 @ 23.98 fps.



6) Verified that the default sequence preset is 23.98 in Audio/Video Settings:



7) Imported .wav file, 48 kHz 16bit stereo file recorded on Tascam DR-40.
8) Imported video file from scratch disk. Had been previously imported via Log&Transfer. Verified it is DVCProHD 23.98:



9) Created two sequences: Seq 1 as DVCProHD 23.98, Seq 2 as Apple ProRes 1920x1080 23.98:



and



10) Located and added marker at sync-clap in video and audio clips.
11) Dragged video into Seq 1 Canvas (the DVCProHD Seq). Dragged audio into timeline and aligned markers. moved audio track until clap was perfectly in sync. Confirmed by listening - no phasing. HOWEVER it is audibly out of sync (phasing detectable by 10 minutes), getting progressively worse. The audio lags the video. There are NO RENDER BARS or color coding on either video or audio clips in the timeline:



12) Exported XML. Opened xml in TextEdit. Sequence and both clips are <ntsc>TRUE</ntsc> and <timebase>24</timebase>


13) Using Copy/Paste and Find/Replace all instances of TRUE were replaced with FALSE. I didn't change the timebase because 24 is correct. Then saved that xml file as a new copy.
14) Quit FCP. Relaunched FCP, but forgot to disable 'open last project', so project opened. disabled setting, quit and relaunched FCP with only untitled project 1 open. Saved that new project with new name.
15) Imported fixes xml file as instructed in tutorial, all options checked, settings on (auto)
SEQUENCE IS STIL OUT OF SYNC! Now I have green render bars on all audio clips!



16) as an experiment, in the xml file I changed ONLY the audio clips <ntsc> parameter to FALSE, but left everything else TRUE. this got rid of the green render bars (See grab below) but IT WAS STILL OUT OF SYNC.



17) I saved this new xml import test project with a new name, closed it, and quit/relaunched FCP.
18) I reopened the project I created in steps 6/7 above. I closed the DVCProHD sequence (Seq 1) and opened the Apple ProRes sequence (Seq 2). Synced up the audio and video as before to the clap. No phasing in first several minutes, phasing progressively worsening until its badly out of sync by the end (70 minutes later.) THis is all same as before. Note that now the video had a green render bar, as expected from putting DVCProHD into a ProRes T/L.
19) Exported and XML of the ProRes sequence.
20) XML file shows that sequence, video and audio are all still <ntsc>TRUE</ntsc> and <timebase>24</timebase>.
21) replaced all TRUE with FALSE , saved as a new xml file
22) saved and quit FCP. Relaunched FCP, created new project by SAVE As. Imported new xml file, Now both audio and video have green render bars. AND IT IS STILL OUT OF SYNC.


Return to posts index


Lars Fuchs
Re: Double system sound Sync issue
on Jan 4, 2013 at 2:58:56 pm

I've spoken to the most experienced and knowledgeable production and post sound specialist I know (decades of experience, feature and tv credit list as long as my arm), and she tells me in no uncertain terms that the problem lies in the Tascam DR-40. As she puts it:

"Note, the DR-40 is well know for NOT running at precise speed. If you record a 12 minute take it could fall off as much as 2000 samples. This can be almost 2 frames by the 10 or 12 min mark. This can be very noticable. Over 71 minutes.... You’re screwed."


I'm not going to run the recorder for more than 10 minutes at a time from now on. Also considering upgrading the recorder!

PS Does anyone know where I can find a resolver for a NAGRA III? I still have one of those running well, just no pilottone resolver alas ;-)


Return to posts index

Matt Lyon
Re: Double system sound Sync issue
on Jan 4, 2013 at 3:39:49 pm

Thanks for the update Lars,

That makes a lot of sense. I was re-reading the thread and was thinking that since you also had the sync problem with Adobe Premiere, that means the issue is likely with the source material, not the software. And given that your thorough testing could not fix the problem, it all makes sense now.

I love Nagras too! But have you tried the Zoom h4n recorder? It's pretty good for the price! (Although I haven't tried running it for a 70 minute take).

Matt Lyon
Editor
Toronto


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]