slowing down time lapsed security video

oneTman wrote on 2/3/2004, 10:49 AM
A client gave me a copy of a piece of time lapsed security survellance video that when played in a regular vtr makes the voices sound like they were sped up by a factor of about 10. I need to slow down the audio enough to tell what the people are saying without it sounding terrible. I know you can "stretch" a piece of video/audio on the timeline in Vegas by up to 10% without deterioration, but this is not enough. Anyone know any tricks or even a third party application that may solve this? Getting access to the vtr it was recorded on is not an option.

Comments

johnmeyer wrote on 2/3/2004, 11:36 AM
I don't think there is anything that can make the audio sound normal if you have to slow it down to 10%. You may not even get something that is intelligible.

Sound Forge is the best tool I know of, although I'm not sure whether it offers anything more than using the Time Stretch/Piftch Shift feature (found in the audio event properties) in Vegas. Start using this tool and see if you can get anything that soulnds like a human voice.
Chienworks wrote on 2/3/2004, 12:51 PM
Is the audio also pitch shifted (sounds like little squeaky chipmunks) as well as sped up? If so, then you don't really want to stretch it. All you want to do is slow it down. Right-mouse-button click on the clip, choose properties, change Method to "Change length and pitch". You can now stretch the event out and it will be the same as if you were slowing down a tape recording. You can go down to 0.25x this way. If you need more, render the result to a new file, put the new file in the timeilne, and repeat. You won't lose anything this way, but with that much of a speed change the audio will probably sound rather dull and muddy. A little EQ may help crisp it up again.
AlanC wrote on 2/6/2004, 8:28 AM
Time Lapse VCR's generally record in 12 or 24 hour mode. 24 hour being the most popular but some machines will stretch this to 48 + hours.

If it's just the audio track that you need to salvage then you should be able to fiddle it as explained already.

However, if the recording is from a multi camera system then it may also include multi track audio and this will add to your problems.

The simplest way by far is to beg/steal/borrow a multiplexer (even the original vcr won't be of any use if it's a multi camera recording). the multiplexer will allow you to select any of the video tracks and play back just that track iin normal speed. You can then capture from the multiplexer's outputs.

If your are in the UK then I may be able to help you with the 'borrow' suggestion.

Alan