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Old February 28th, 2013, 11:48 AM   #1
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Synching video with audio

I slated my footage & audio and import the AVI & WAV into my editor.

Video is running at a nominal 30 FPS, (or 33 milliseconds per frame)
My Audio editor runs at 10 millisecond granularity.
So, there are instances where the Video & Audio can be off by 5 millisecond.
I realize this is so small as to not matter, but it does lead to the following question:

Is it better to have the audio be ahead of the video, or the video be ahead of the audio.

I also realize that in normal on-camera recording, when I am 9 feet away from subject, the video is about 8 milliseconds ahead.
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Old February 28th, 2013, 12:30 PM   #2
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Re: Synching video with audio

It is definitely better for the video to be ahead of the audio. I have seen an IEC study that shows this clearly. From memory, the audio can be delayed by 40ms and be acceptable, but can only be advanced by 10ms before it becomes objectionable.

The exception is when displaying in a large theater. If you are tuning the audio timing for a seat 30 feet from the screen and speakers, you can advance the audio by 30ms compared to the nominal timing.

For publication on the web, people often listen on headphones, which has virtually no delay from speakers to ear, so don't advance the audio for web publication.
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Old February 28th, 2013, 01:04 PM   #3
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Re: Synching video with audio

Use Vegas and you can bring them in sync and even squeeze or expand audio to account for clock differences between the video and audio recorders.

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Old February 28th, 2013, 02:09 PM   #4
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Re: Synching video with audio

Vince, what audio editor are you running?

Like Ron, I love using Vegas' sub-frame audio editing. Down to sample-level, or 1/48,000th of a second.
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Old February 28th, 2013, 02:21 PM   #5
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Re: Synching video with audio

Quote:
Originally Posted by Seth Bloombaum View Post
Vince, what audio editor are you running?
Would you think less of me if I told you Audacity?
I have Sony Acid, but I have never loaded it.
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Old February 28th, 2013, 06:19 PM   #6
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Re: Synching video with audio

Nothing wrong with Audacity - there's a lot of professional work done on it. It has its limitations but within those limits it's a fine product.
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Old February 28th, 2013, 07:09 PM   #7
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Re: Synching video with audio

I'm with Steve on that - Audacity is a fine project, and very capable. I've recommended it to people who need a simple sound editor, but, never thought about it for sound for picture. Seems like 10MS ought to get you close enough. Can you see picture while you're editing sound?
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