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1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions

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zoe west
1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 13, 2012 at 12:38:35 pm

Hi everyone

I usually work with HD projects set up as 1080p/24 and I have just inherited an avid HD project which has been set up as follows

1080p/23.976
35mm 3perf
Sound recorded at 30fps 48.048

Everything syncs up fine in the avid and all looks great, but having always worked with 1080p/24 and PAL projects, I just want to get my head around this new workflow, and find out if there is anything I should be checking. The sound department will be joining us in a few weeks and I know they are used to working with 24 project as well. So any advice/tips/ info would be gratefully appreciated.

I am setting up a mini conform test this week

Many thanks

Zoe


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Job ter Burg
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 13, 2012 at 2:16:05 pm

Zoe, this implies they shot picture at 24.000fps, but then transferred at 23.976 with the intention to post at 23.976. Fairly common for US productions.

Sound was shot 48048, then slowed down to 48000 during import (Avid can detect pulldown sample rates and import them sample-by-sample). This slows the sound down by the same percentage as picture is being slowed down.

The 30fps is just the timecode. Doesn't make much sense in HD projects to have a 30fps timecode, but Avid will allow it.

After that, everything is to be treated as if it were shot at 23.976, and is to be posted at 23.976.


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zoe west
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 13, 2012 at 4:46:51 pm

Hi Job

thanks for the quick reply. Yes picture was recorded at 24. Okay, so in theory all should be straight forward

Thanks


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Michael Phillips
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 14, 2012 at 1:27:44 am

Job is correct in the workflow explanation for 24.000 production and 23.976 shoot. The one addition I would add or caution you about is the need to track the 30fps timecode on the audio BWF files as part of the conform process and if that is part of your test.

If so, you should know that MC tracks 30fps in the SoundTC regardless of project timecode rate. And while this may seem to work for your particular workflow, you will need to do a few steps in order to get the 30fps into that field if importing BWF directly into the project for syncing. Here are two ways:

1. Import 30fps BWF into a NTSC 23.976 project. Select the correct TC in import dialog of 30fps. The 30fps timecode will be preserved and available in the START. Highlight the START column and do a command-D or control-D and select SoundTC from the pop-up dialog box. Open these bins in your 1080p/23.976 project and sync. You will now see that the original 30fps timcode is being tracked in the SoundTC column as the original TC rate of 30fps. All EDL generation should use the SoundTC as source.

2. In your 1080p/23.976 project, import BWF and select correct TC rate in import dialog of 30fps. You will see the converted TC that will bed up in the START column after import. Making EDL's from this will not work as the timecode will not be the same. Highlight the START column and do a command-D or control-D and select TC30 from the pop-up column. This will convert the 24TC back to the original 30TC (undoing what it did in the import). Because of rounding errors in calculations from 30-24-30 - you may see +/- 1 frame from your original BWF timecode. All EDL generation for BWF should now use the TC30 column.


Productions planning on HD post in 1080 for 24/23.976 productions should really consider 24fps timecode on set so that you have a 1:1 timecode relationship between picture and sound and all source TC is being tracked in the START column with no farther need to track in alternate columns. 24fps film and 30fps for audio is a leftover of NTSC film transfers of several years ago.

And while you can still make this combination work, it is worthy of a discussion with the production and post team as to why.


Michael

Michael Phillips


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Job ter Burg
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 14, 2012 at 8:22:10 am

Michael, wouldn't it be easy to convert the TC stamp to 24 using something like Wave Agent, then?


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Michael Phillips
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 14, 2012 at 3:16:07 pm

I don't know if I would suggest that right off the bat as it will no longer match smartslates and anything else that may have been using the timecode on set. These are decisions that need to be made before rolling (or spinning) the camera. The two methods I propose aren't time consuming, but intended to preserve original source metadata for possible downstream needs.

Michael

Michael Phillips


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Bouke Vahl
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 15, 2012 at 9:47:51 am

I don't get it.
Where is the framerate defined in a BWF file?
Nothing about that in the specs as fas as i know.
Thus, it should be possible to assign any TC rate to the clips...

Bouke

http://www.videotoolshed.com/
smart tools for video pros


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Job ter Burg
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 15, 2012 at 11:54:32 am

Like Michael said, it may work, but not for all intents and purposes, e.g. on-set smart slates would have already been at 30fps. Changing the BWF TC stamp afterwards then works for the BWF, but won't change the smart slate code. Not a problem when you start at round seconds, of course, but what if you don't?

And again, Avid can track these codes.

Old habits die hard, which is why many folk stick to 30fps TC for sound (and 25fps in the PAL world even on 24p shoots), even though it makes hardly any sense in an all-HD workflow.


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zoe west
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 22, 2012 at 8:49:38 am

Hi Job

I've used Wave Agent to change 25fps sound to 24fps on a previous project, when it was incorrectly recorded on set at that frame rate for a few days, and it worked like a dream.

Thanks

Natasha


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zoe west
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Feb 22, 2012 at 8:45:53 am

Hi Michael

Thanks for this. I inherited the production at the end of the shoot, and ii believe that the sound was imported as per Method 1. The Sound TC has also been burnt in to the picture, which has been helpful.

In the past I have always had sound recorded at 24fps on set.

The Sound Designers have just been confirmed, so I'll do some tests with them this week.

Thank you for all your help

Natasha


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Zoe N West
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Mar 5, 2012 at 5:32:42 pm

Hi Michael, Job, Bouke

I have another question regarding this workflow, if you wouldn't mind shedding some more light :)

I have done some tests with the Post Sound Team, and we now appear to be in sync. The EDL's I generate for them with Record TC as TC1 seem to work.

What they are doing is converting to 48 kHz mono files. Then they conformed my EDL in their audio session using 30 fps source code and 24 fps destination code, and it worked!

The QT's I give them to work with are at 23.976, however they believe that the audio on the QT's is 48.048 and not 48, and they believe I should be supplying them with QTs that have 48 sound on them. However I can't see a way of altering these settings at all. Is what they are asking correct?

Eventually the audio supplied by the sound house will need to be 24fps on the MO disc to sync with the picture negative and also for use on the DCP.

Many thanks for all your help so far

Zoe N x


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Zoe N West
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Mar 5, 2012 at 5:45:47 pm

Hi Michael, Job, Bouke

I have another question regarding this workflow, if you wouldn't mind shedding some more light :)

I have done some tests with the Post Sound Team, and we now appear to be in sync. The EDL's I generate for them with Record TC as TC1 seem to work.

What they are doing is converting to 48 kHz mono files. Then they conformed my EDL in their audio session using 30 fps source code and 24 fps destination code, and it worked!

The QT's I give them to work with are at 23.976, however they believe that the audio on the QT's is 48.048 and not 48, and they believe I should be supplying them with QTs that have 48 sound on them. However I can't see a way of altering these settings at all. Is what they are asking correct?

Eventually the audio supplied by the sound house will need to be 24fps on the MO disc to sync with the picture negative and also for use on the DCP.

Many thanks for all your help so far

Zoe N x


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Michael Phillips
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Mar 5, 2012 at 6:56:00 pm

Once audio is imported into Avid, it can only be 44.1 or 48Khz. In the 48.048 workflow, it gets restamped as 48kHz and end up being a sample for sample playback, thus slowing it down .1%. Anything in Avid, is now 48kHz, including exports which have no control over sample rate when it comes to +/- .1% workflows.

Michael

Michael Phillips


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Zoe N West
Re: 1080p/23.976 sound recorded at 30fps 48.048 - workflow suggestions
on Mar 7, 2012 at 1:16:00 pm

Great thanks Michael, that's what my understanding was, I'll re-iterate to the Sound Dept

Zoe N


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