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  #1  
Old 04-03-2008, 09:52 AM
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nucelar nucelar is offline
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Default Tick-based sync solution?

Hi all!
For reasons of urgency out of our control we had to dub a film into spanish using the video ripped from a DVD instead of a proper PAL digibeta master. Nasty, I know...
Well it turns out the digibeta master now arrived but is shorter than the digibeta master by a factor aproximately (but not exacly) 0,9590 (-4,1%).
Has anybody used the tick-based audio option and modified the bpms in order to sync it that way instead of using time compression? Is this a good idea?

Thanks
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Old 04-03-2008, 10:21 AM
froyo froyo is offline
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Default Re: Tick-based sync solution?

Hello. Tick based audio tracks do not perform any time compression or expansion on the audio files if the tempo is changed. The only thing they do is switch their 'sync' points. For example say the region syarted at 01:02:00:00 at a tempo of 120 bpm; if the tempo was changed to 130 bpm then the region would move up a frame or two or a few to now start at 01:01:59:27. I don't know the actual numbers but you get the idea. The audio itself would not be changed, no time compression or expansion or sample rate conversion. Elastic audio tracks would do this (except SRC) but not tick based audio tracks.

In any event your best bet is to sample rate convert your session with a Pull Up of 4.1%. Create a new session, import the tracks with Pull Up and you should be in business. Good luck.
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Old 04-03-2008, 02:09 PM
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Default Re: Tick-based sync solution?

Hi there,

First, you should understand that elastic audio (whether tick-based or sample-based) uses the same basic TCE processes as a time compression/expansion plugin. Most of these will create subtle artifacts when processing. However, the Vari-Speed algorithm just speeds up or slows down the recording (resamples it at a different rate) and will not degrade audio quality - similar to speeding up a 24 fps film to transfer to PAL.

Tick-based Elastic Audio is not what you want here, but you can use sample-based Elastic Audio for this with the tracks set to use Vari-Speed. Using Elastic Audio will be a little easier than using a Vari-Speed / Resampler Audiosuite plugin on its own, because you can tweak, adjust, and preview the playback & alignment before committing the change. You can enter the exact percentage of playback rate change in the Elastic Properties dialog. If you don't know it exactly, you can also go manually align the ends of the audio with the video so that it's playing at the correct rate.

So Elastic Audio will be helpful here, but don't try using tick-based to do this - it'll be too complicated. Sample based tracks will work better.

I hope that helps.
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Old 04-03-2008, 02:20 PM
froyo froyo is offline
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Default Re: Tick-based sync solution?

Hello. Paul thank you for those comments explaining the ins and outs of Elastic Audio. Don't you think the best bet here is to use sample rate conversion? As I understand the issue the Digibeta is PAL and the DVD is probably NTSC which accounts for the 4.1% difference in length. In doing the SRC, the entire project is synched up in one pass. Going with Elastic Audio here would be quite a laborious undertaking and quite unecessary also.

If the drift is not constant or random then maybe Elastic Audio can help but as it stands SRC is the way to go I should think. If the drift is found to be something other than the 4.1% Pull Up, the exact figure can still be figured out and an appropriate sample rate can be entered to achieve a tight sync.

Paul do you feel Elastic Audio is a better option than SRC for this problem, or were you merely explaining Elastic Audio in case anyone was interested?
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Old 04-03-2008, 03:29 PM
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Default Re: Tick-based sync solution?


Hi there,

I was mostly giving background on EA to explain that tick based elastic audio would not be the best bet for this, but that you could use sample based if you needed to (particularly if you're done editing and just need to do it on the bounced / consolidated session).

That said, doing SRC on the whole session is a good solution.
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Old 04-04-2008, 04:19 AM
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Default Re: Tick-based sync solution?

Hi!
Thank you all for your explanations, they are very helpful. I will try the SRC on import and see what happens. Never had the need to do this before...
My original intention, though, was to not apply *any* processing to the audiofiles, just to place them in the correct spot in the timeline. But I see that although the beginning of each take would be at the correct spot it would go out of lipsync after few seconds..
Bye!
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