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synch problem with D5 mark II rush

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Deep Chattopadhyaya
synch problem with D5 mark II rush
on Dec 1, 2012 at 11:58:46 pm

Hi,

DOP changed the camera settings after the first three shots of the first day of the shoot from 25fps to 23.98 fps and it was only discovered when the rush came to the editor, thats yours truly. The sound was recorded separately and I have no idea at what frame rate the sound recordist time-coded it.

The rush was ingested through EOS Movie plugin E1 (H264 to Apple Pro Res) at 23.98fps and I tried to synch it by using pluraleyes. The synch stays in place for initial few seconds and then starts deviating.

After reading various forum posts for last two weeks, I have tried the following with no effective results :

1. Conformed the video from 23.98 fps to 24 fps by using Cinema Tools. Created Sequence Preset 1080p with editing timebase :24fps. Imported the audio clip after creating the new sequence preset and then modified the timecode of the audio clip (Modify-Timecode- Deselect Source- Select Current) and then put it in the new sequence timeline.

2. Repeated the same for 25fps creating the Sequence Preset accordingly.

The clips still continue to go out of synch after few intial seconds.

My questions :

1. Where am I going wrong? How can I put into synch?

2. What is the best workflow for rush shot in 23.98? (This is a documentary which will only have digital 2k projections)

I will really appreciate any suggestion to solve this.

Best regards.


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Rafael Amador
Re: synch problem with D5 mark II rush
on Dec 2, 2012 at 2:47:10 am

Hi Deep,
Going to 24fps makes sense only if you are printing to 16/35mm film.
If you are not printing to film, stick with 23,98fps.
Conforming footage affects to the speed that audio is played, so the clips and the audio files will have a different play speed and even if you sync them with Pluraleyes, the audio will drift.

About your Audio out of sync problem:
FC has an old bug.
When you import audio files (aiff, wav), FC treat those audio files as they had the same time-base of your default sequence.
So if you are in PAL land and your default sequence (Sequence Presets) is 25fps, FC will take that audio as if was recorded with a 25fps Time Code, even when the audio has no Time Code.
So when you open a new sequence with a different time-base (23,98, 24, 30..). the audio will go out of sync.

The solution is to, before importing the audio, set a default sequence with the same time base that you intend to edit the audio.
rafael

http://www.nagavideo.com


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Michael Phillips
Re: synch problem with D5 mark II rush
on Dec 2, 2012 at 4:18:23 pm

When you change the rate in Cinema Tools, it does a frame for frame conversion in the NLE resulting in a speed up or slow down. You are looking to a frame rate conversion that does not change duration, but fills in or removes frames/fields as needed to do so. So a 1 minute clip is still 1 minute regardless of frame rate. Audio does not have a frame rate per say, but a sample rate/second. Time is time, so as long as you convert video to "time" it will stay in sync. Audio will adjust to time of you record in pullup/pulldown modes such as 48048 and 47952 with a sample for sample playback rather than a true sample rate conversion that maintains original duration. Depending on NLE used, each have their ways to deal with this.

Michael


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Deep Chattopadhyaya
Re: synch problem with D5 mark II rush
on Dec 2, 2012 at 5:11:09 pm

Hi Rafael,

Thanx for your reply. I knew about this bug reading your earlier replies in other posts. So I was careful in creating/altering the Sequence Preset every time I conformed the video to 24fps or 25fps.

I tried once more with 23.98 fps and the sound is still out of synch. Then I remembered that the timebase of audio files can only be whole numbers i.e 24fps thus it is obvious that the synch will be off with 23.98 fps video.

That is why I conformed the video to 24fps and 25 fps to do some tests and checked the synch and it is still out of synch.

If the editing timebase of audio files can only be 24 or 25fps (i.e whole numbers), is there a point sticking to 23.98fps for the whole project?

Anyway , I need to first solve why the synch is still eluding me, that's the first step to resolve and then to plan the whole workflow.

Any other suggestions?

Many thanks,

Deep


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Michael Phillips
Re: synch problem with D5 mark II rush
on Dec 2, 2012 at 8:11:18 pm

Audio has 48000 sample per second regardless of how you want to divide up the frame count within those 48000 samples (23.976, 24, 25, 39.97, 30, etc,). The frame rate and timecode have no bearing on sync playback as it can always be ignored and there will still be 48000 samples for every second. Timecode and framerate is used to reference a sync relationship to video which does have frames. But since your recording devices don't support timecode, it really is only about sample per second and ensuring those are consistent for the entire recording time during production.

Drift is usually an issue of unstable clock or recording other than 48000 and played back sample for sample resulting in a pullup or pulldown as in the case of 48048 and 47952 workflows.

Michael


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Rafael Amador
Re: synch problem with D5 mark II rush
on Dec 3, 2012 at 9:22:32 am

[Deep Chattopadhyaya] "Then I remembered that the timebase of audio files can only be whole numbers i.e 24fps"
That makes no sense.
Audio don't know about "frames", don't knows about time-bases.
As Michael say, the Sampling Rate is his own time-base. If an audio has been recorded at 48Khz, means that every 48.000 samples makes a second, and that every second have to be played 48.000 samples whatever the application that manage it.

Have a look in FCs Browser to the 24fps clips you have conformed. You will see that the Sample rate is not anymore 48Khz.


[Deep Chattopadhyaya] "Imported the audio clip after creating the new sequence preset and then modified the timecode of the audio clip (Modify-Timecode- Deselect Source- Select Current) and then put it in the new sequence timeline."
You said that you modified de TC audio.
That is a "destructive" operation, meaning that changes the properties of the original files.
If your audio was recorder with something like a Zoom H4, the files havs no TC, but is possible that with you modified them, you have put an TC track.
I would have a look to the Audio clips Properties (open with QT.7 > Cmd-J) and see if there is any TC track.
In case there is, delete it.
rafael

http://www.nagavideo.com


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Deep Chattopadhyaya
Re: synch problem with D5 mark II rush
on Dec 3, 2012 at 10:47:08 pm

Hi Rafael,

I opened the audio file (wav) in QT7 and it does have a timecode track. I deleted it but could not save it except as a .mov.

What do you suggest?


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Deep Chattopadhyaya
Re: synch problem with D5 mark II rush
on Dec 4, 2012 at 9:49:37 am

Hi,

Finally it got solved today. I needed to rename the audio clip and imported it in a 23.98 sequence and bang it synced.

Many thanks to all of you.


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Olivier Bertin
Re: synch problem with D5 mark II rush
on Jan 19, 2013 at 5:04:19 pm

Hi,

I have a similar problem:

I have footage captured on a 5D Mark II @ 23.98 that is matched with sound recorded separately at 96/24.

Now, we worked at 23.98 with ProRes (Proxy) for the edit in FCP7 and we now have our final cut at 23.98. I have conformed the project in ProRes 422 (HQ) and am now looking at exporting for sound.

The problem is we need to output two masters of the same project:
- one 23.98 HD version for video
- one 24p 2K project to create a DCP

So, I'd like to send the mixer one file that I can then import back in either a 23.98 or 24p timeline without any synch issues.

I've been doing tests on the first 10 minutes of the film and haven't been able to get the synch to work properly with the audio still clocked at 96kHz.

The trip through Cinema Tools changes the sampling frequency to 96,096Hz (which we don't want). I can import the conformed video back in a 24p timeline without any issue, but when I try to synch it to an .aiff export from the same segment, the sound eventually shifts.

Any suggestion?

Thanks!

Olivier


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Michael Gissing
Re: synch problem with D5 mark II rush
on Jan 20, 2013 at 10:44:35 pm

Firstly your audio for a DCP should be 48khz. Work with the 23.98 version and get your mix synced.

Then export a self contained QuickTime using current settings with the mix audio. Take that QuickTime into Cinema tools and change the frame rate to 24. Job done.


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Olivier Bertin
Re: synch problem with D5 mark II rush
on Jan 21, 2013 at 2:28:54 pm

Michael,

Thanks for your reply. We're keeping everything at 96kHz until the last minute. I think I had read somewhere that 96kHz was also possible for a DCP (might be wrong, not familiar with it).

On the other hand, if I do what you suggest, I end up with a 24p frame rate, but my sound is clocked at a sampling rate of 96,096Hz (or 48,048Kz) and it won't be accepted.

I'm really banging my head against the walls with that thing, because I can't figure out why the synch is off regardless of the frame rate. 1 second is 1 second in time whether it's divided in 23.98, 24 or 60 frames, and it should match 1 second of sound regardless of its sampling frequency...

I'll keep digging.

Olivier


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