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Time Remapping / Time Adjusting

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Ben BarnesTime Remapping / Time Adjusting
by on Sep 16, 2008 at 4:12:05 am

I have a one-shot music video I need to sync up to audio. The playback we used was a little off, so I need the video to run at roughly 98% of its normal speed to sync up to the music track, as the video runs slightly longer than it should.

Adjusting the speed of the clip in Final Cut works okay, but I notice the stutter when the program repeats a frame in its adjustment. Will time remapping in After Effects do a better job? Any advice as to the best way to do this?

Thanks in advance

Ben


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Chris WrightRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 7:14:41 am

Could it be 98.75%? I know that is the difference between 29.97 and 23.976. If the audio was crystal synced or digitally synced and you didn't use a low end tape recorder, then all you have to do is either speed up the audio or slow down the video. Audio changing is the professional way, and less problems than video changing, hence video artifacts from framerate changing.

Hopefully, all you have is a normal 0.1% speed change. Because then you know the exact speed number. If not, line up timecodes from head to tail slates and frame accurate sync in AE by streching audio speed to duration and enabling high quality audio remapping with pitch correction.

*********Techie read article*****

The short version of this tutorial is to use 29.97 fps timecode for video, whether it be regular NTSC, 30P/24P "film look", or prosumer High Def video.

When shooting actual 24fps or 30fps motion picture, then you have to deal with the 0.1% speed change, so keep your audio at 30fps timecode. Live dialog will end up being slowed down to 29.97 during transfer to video; but sync playbacks will be speeded up from their original 29.97 to 30 fps when played back on the set.

http://www.equipmentemporium.com/Articles/audiosyncplayback.htm



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Ben BarnesRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 3:36:48 pm

i'm pretty sure it's around 98.0 / 98.2. I don't know exactly how it ended up off, but I shot at 36fps, converted the track to 66.67% of its length in peak, and used it in playback, threw it up into a 24fps timeline, and was out of sync.

if i wanted to adjust audio instead, what's the best way to do it to a music track to preserve the highest quality? the band is anxious about making the track sound bad in any way.






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Dave LaRondeRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 3:47:14 pm

[Ben Barnes] "...I shot at 36fps..."

How did you do THAT? Certainly not with any video camera I'm familiar with. So was it a film camera? And if so, at what frame rate was it telecined?




Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Ben BarnesRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 4:13:23 pm

we shot on an hvx at 36fps. the raw footage imported as the usual 23.976 fcp quicktime with the DVCProHD 720p60 codec


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Dave LaRondeRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 4:30:31 pm

Oh. I knew an HVX shot at a lot of frame rates, but not that one.

Okay, now here's another question: is this 36fps a real integer frame rate like 24fps film or 25fps PAL, or is it actually an NTSC-oriented frame rate containing a fraction, like 23.976, 29.97 or 59.94?

If it's NTSC-oriented, the actual frame rate could be something like 35.964, which might explain the variation.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Ben BarnesRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 4:40:16 pm

thanks for the info. i don't see a different way of importing/interpreting the footage to account for the discrepancy you're talking about, as the quicktime converted from the xml data is preconverted to 24P.

i guess my question now is, if i time remap in AE, will i still get the same (barely noticeable) frame duplication every however many frames that i get in FCP, or is it more seamless?

If I resample the audio to be 1.8% faster, is there a basically lossless method of resampling? i mean adjusting for time without changing pitch.



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Dave LaRondeRe: Time Remapping / Time Adjusting
by on Sep 16, 2008 at 4:54:41 pm

[Ben Barnes] "If I resample the audio to be 1.8% faster, is there a basically lossless method of resampling? i mean adjusting for time without changing pitch."

Oh, sure, 1.8% isn't a whole heck of a lot. You can do that in Soundtrack Pro, if you want.

Personally, I like a freebie audio application for Macs called Audacity. Just about the only thing I use it for is changing the length of audio files without changing pitch. You can dial in a change in duration in hundredths of a second, or you can use a percent change. If you try it, use the Change Tempo effect.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Chris WrightRe: Time Remapping / Time Adjusting
by on Sep 17, 2008 at 9:25:57 am

***quicktime converted from the xml data is preconverted to 24P. ***
Don't you mean 23.976 not 24p?

and AE's timewarp pixel motion won't have any stutter, duplicate frames, motion blur, or weird frame blend you might get not using full pixel conversion, but it can be tricky to setup around cuts or transitions.





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Ben BarnesRe: Time Remapping / Time Adjusting
by on Sep 17, 2008 at 3:17:43 pm

yes, 23.976. The whole video is one shot, so i'll give pixelmotion a try. thanks.



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Ben BarnesRe: Time Remapping / Time Adjusting
by on Sep 22, 2008 at 9:56:34 pm

pixelmotion really didn't respond well to any short bursts of light, which my video has some of, so I'm going to try to use change duration to shrink the duration of the song to 2%.

The problem is, in Audacity, Peak, even Soundtrack Pro, changing the duration makes the song sound terrible, just warbly and awful.

Is there a program / technique where I can make an audio track (aif) 98% of its regular length, preserve pitch, and have the song sounding as good as the original?

Help!

Ben



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Chris WrightRe: Time Remapping / Time Adjusting
by on Sep 23, 2008 at 3:01:51 am

This method below is used professionaly for movies. Also soundforge is good.

After Effects itself will do a remarkably good job of this stretch if you follow these instructions: Import your audio separately from your video. Place it in your fps comp. With your footage selected, reveal the tab for Stretch (or select Time Stretch from the Layer Menu) and enter %. Now from the Layer Menu select Enable Time Remapping. This last step is very important as it triggers After Effects to use a very high quality audio re-sampling technique.








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