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Old July 14th, 2014, 11:41 AM   #1
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Inconsistent Play Speed on Old Video

A few years ago, I used a basic home camera (with a little DV tape) to record a Christmas light display I built in my living room. One of those things with relays and lights flashing to music - custom programmed.

Problem: Somewhere along the way, (recording to camera, or recording from camera to computer) the video speed became variable. It's difficult to explain, and thus difficult to Google.

Parts of the video play faster than others. So the beat of the song is like: "X...X...X...X...X...X...X...X...X...X...X...X..X..X..X..X..X..X...X...X...X...X...X...X...X...X...X ...X..X..X..X..X..X..X...X...X...X...X...X...X...X...X" (see how some X's are slightly closer together?)

Iím looking for a way to stretch the video, where necessary, to achieve a consistent beat. Do any of you have any ideas?

I figure there's gotta be software out there to do that for audio to make bad garage bands sound better than they are - so perhaps there's one that does something similar for video.
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Old July 14th, 2014, 12:42 PM   #2
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Re: Inconsistent Play Speed on Old Video

I use Sony Vegas Pro, which has a quick and easy 'time stretch' process: 'Shift/drag' the event/clip's end. An sync reference audio track makes things easier, but it should work otherwise. Don't know about the VP demo or low cost 'Movie Studio' version

OTOH, most audio DAWs/editors and NLEs have some kind of time stretch option. May not be as quick and easy as Vegas though.
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Old July 14th, 2014, 01:11 PM   #3
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Re: Inconsistent Play Speed on Old Video

Awesome, thank you!

I will check with some friends to see if anyone locally has VP and perhaps I can use their computer to do it.
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Old July 14th, 2014, 02:36 PM   #4
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Re: Inconsistent Play Speed on Old Video

Hi Keith,

I don't see how it would be remotely possible for your video speed to vary when coming from a digital format such as MiniDV. Or any video format for that matter - if the frame rate varied, it just wouldn't play back at all, must adhere to video timing specs.

What's more likely is that the camcorder might have been set to record 12-bit 32k audio and you're editing in the standard 16-bit 48k mode. Take another look at the workflow, I guarantee the video is not recorded at a variable frame rate.

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Old July 14th, 2014, 02:48 PM   #5
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Re: Inconsistent Play Speed on Old Video

That certainly could be the case. I had better check the video again to make sure it wasn't my mind that was glitching.

I forgot that MiniDVs had the time codes, and I'm pretty sure this was recorded on miniDV. Maybe my inlaws still have the tape even.
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Old July 14th, 2014, 07:36 PM   #6
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Re: Inconsistent Play Speed on Old Video

It's normal for audio & video to drift apart some, even under the best of conditions. If the sync 'error' is significant, it very well could be a sample rate mismatch as Jeff stated, however the pitch would also be affected which is 'usually' noticeable. Make sure your NLE is set to 48kHz, the standard rate for NTSC/ATSC video. If the original audio was recorded separately on an audio recorder @ 44.1 it would need to be re-sampled to 48k prior to ingesting.. unless one has Vegas (or other NLE) which supports mixed sample rates. VP supports multiple sample rates and bit depths within the same project.. or even the same track for that matter.
BTW, Time code by itself does not guarantee a drift-free playback or make much difference for a two or more camera shoot or second system audio for that matter. A tri-sync system is the norm these days for projects requiring absolute frame accurate sync.
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