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audio drift with dslr footage

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Margo Guernsey
audio drift with dslr footage
on Dec 13, 2010 at 6:40:08 pm

audio drift - help!!!!!

I have a fcp sequence with dlsr footage from a canon 5D at 30fps mixed with archival footage and clips exported from AE at 29.97. The original sequence settings were Apple ProRex 422 proxy 30fps. The audio drift is horrible.

When I export an aif and import the same aif, it comes in about 1 second shorter than the video, creating a horrible audio drift. I am mixing audio in protools so i need to be able to reimport the audio and have it be in sync.

The sample rate for all audio is 48.

I tried creating a new sequence at 60i and 29.97 and copying the footage into it, and that didn't help.

I have tried exporting the project as an XML, changing the ntsc tags so they all say TRUE and reimporting it into a 29.97 sequence and that didn't help.

Any advice? I'm at my wits end.


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Chris Wright
Re: audio drift with dslr footage
on Dec 13, 2010 at 8:19:10 pm

since you'd probably want to conform the 30fps to 29.97. simply import the original 30fps into AE as a new comp(30) at 30fps, then rightclick timestretch 100.1001001. make a new comp at 29.97 and place (30 comp) in there and render out 29.97.

This will slow down the video AND audio 1% so they both match each other. You will need to re-edit your final product, but everything will sync. also make sure you have AE updated. there was a aif bug.

also you could use Cinema Tools to optically change framerate if you did't want to change the video/audio speed(unnoticeable) but it could take a long time to render.

http://technicolorsoftware.hostzi.com/


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Margo Guernsey
Re: audio drift with dslr footage
on Dec 14, 2010 at 1:59:29 am

If I understand this correctly, I should include the audio and the video when I set up the new AE comp. Or should I do this with just the video? At this point the audio has been mixed in protools so I could cut it up to match it to the pieces that go with the video, but I think it makes sense to conform the video only.

Am I right?

Thanks a million.


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Chris Wright
Re: audio drift with dslr footage
on Dec 14, 2010 at 7:55:26 am

my post was made in the understanding that you have recorded synced sound from your camera at 30fps. the 1% slowdown would not only keep the original in sync, it would also sync to the rest of your final edit and have the added bonus of matching framerates.

Like I said before, either you slow down BOTH at the same time using AE's timestretch or cinema tool's conform, or you use optical flow plugins like compressor or twixtor to conform to 29.97.

You may have put a lot of time into the pro tools edit, so compressor or twixtor may be less painful than replacing all the tracks by hand although the rendering time will be very high. I say the time to go either direction is about the same, ironic huh?

http://technicolorsoftware.hostzi.com/


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Margo Guernsey
Re: audio drift with dslr footage
on Dec 14, 2010 at 4:10:37 pm

No, the footage is definitely not synced footage shot on the 5D.

So, I should export the 30fps clips, use compressor to conform them to 29.97, and then reinput into fcp?

Is twixtor better than compressor or is it the same? I've never used it.

Does it matter what settings I use for the sequence fcp as long as it is 29.97?

Thanks again. I'll do anything at this point to fix this!


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Chris Wright
Re: audio drift with dslr footage
on Dec 14, 2010 at 8:56:29 pm

Why isn't the original 5D synced? was it a double sound system and they screwed up on the production speed? You can find out how badly they recorded by aligning the rate stretch tool in premiere with the waveform lip sync.

Compressor has less artifacts than twixtor, but you can't optically change the fps because your audio is out of sync to begin with! FCP needs all footage to have the same fps.


This is what I would do.
1. If I couldn't find out the production sound speed, I'd sync up the audio to the original with premiere's rate stretch tool to the waveform of obvious silibants. (The farther away the 2 wavecrests you choose, the more accurate the sync)

2. Once synced up, I'd open compressor, click conform to 29.97, or timestretch in AE,(will then slow down both the video and audio to 29.97.) or optical flow.

3. edit in FCP then master in pro-tools.

The reason you can't take any shortcuts is because your framerate is messed up too, not just your unknown audio speed.

And if this sounds like a nightmare, hire a better crew next time.

http://technicolorsoftware.hostzi.com/


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Chris Wright
Re: audio drift with dslr footage
on Dec 15, 2010 at 12:23:15 am

are you positive the recordings are at 48khz and didn't get resampled at 44.1? can you go to the original recordings and file-properties?
the khz can act as speed just like fps in video.


http://technicolorsoftware.hostzi.com/


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Margo Guernsey
Re: audio drift with dslr footage
on Dec 15, 2010 at 7:30:48 pm

I am sorry I wasn't clear. Its not synced because it was never meant to be synced. All of the video is MOS. The sync I was referring to is narration in my fcp project that is lined up. When I export to aif, mix in protools, and reimport, it drifts out of sync.

Anyway...

I conformed the video in cinema tools and am converting to Apple ProRes in compressor right now and then going to use a 29.97 sequence in fcp. Fingers crossed. Thanks for your help!


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