Synching video with audio at DVinfo.net

Vince Pachiano · February 28th, 2013, 11:48 AM

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.

Jon Fairhurst · February 28th, 2013, 12:30 PM

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.

Ron Evans · February 28th, 2013, 01:04 PM

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.

Ron Evans

Seth Bloombaum · February 28th, 2013, 02:09 PM

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.

Vince Pachiano · February 28th, 2013, 02:21 PM

Quote:

Originally Posted by Seth Bloombaum

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.

Steve House · February 28th, 2013, 06:19 PM

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.

Seth Bloombaum · February 28th, 2013, 07:09 PM

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?

February 28th, 2013, 11:48 AM	#1
Vince Pachiano Major Player Join Date: May 2008 Location: Dayton, OH Posts: 307	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.

February 28th, 2013, 12:30 PM	#2
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	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. __________________ Jon Fairhurst

February 28th, 2013, 01:04 PM	#3
Ron Evans Inner Circle Join Date: Mar 2003 Location: Ottawa, Ontario, Canada Posts: 4,220	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. Ron Evans

February 28th, 2013, 02:09 PM	#4
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	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. __________________ 30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.

February 28th, 2013, 06:19 PM	#6
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	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. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

February 28th, 2013, 07:09 PM	#7
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	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? __________________ 30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.