Vegas recorded WAV loses sync with DV Tapes

Cooldraft wrote on 5/11/2007, 3:53 PM
I am using Vegas and an Alesis Firewire Mixer to record seperate channels for each input. When I go to the time line, I can line all the cameras up woth no problem, but the 7 wav files that vegas recorded slowly get out of sync with the Tape (and even the MP3 backup recorder). Is there something that I should know about this?

Comments

John_Cline wrote on 5/11/2007, 4:41 PM
Yes, even though all the recording devices are crystal controlled, none of them are running at exactly the same frequency. Therefore, they are guaranteed to drift. Fixing the problem is fairly easy in Vegas, align the audio files at the beginning and then grab the end of the audio track and hold down the Control key and lengthen or shorten them to match the video's audio tracks.
Cooldraft wrote on 5/11/2007, 9:40 PM
does this mean my notebook is going south? 5 cameras, 2 MP3 Recorders remained synced and the only thing that gets off was the Vegas WAV files. I thought it might me the wav (lossless vs DV/MP3). I will try to use your suggestion on stretching. Sounds like it should work.
John_Cline wrote on 5/11/2007, 10:10 PM
No, I doubt that your notebook is going south, it just means that the Alesis Firewire unit's clock is slightly off. How far did these files drift over what period of time?

John
PeterWright wrote on 5/11/2007, 10:31 PM
After lining up a common sound at the beginning and Ctrl/Dragging to match a sound near the end, be aware that this stretch will slightly change the position of the beginning sound, so re-align and re-check.

Did you use the same sample and bit rate as DV (48/16). This can make a difference, as well as different clocks, as John says.
CClub wrote on 5/12/2007, 7:47 AM
Will this procedure you both outlined also work in re-syncing an MD recorded WAV file that has drifted a bit from a camera's audio tracks?
John_Cline wrote on 5/12/2007, 8:04 AM
yes.
Cooldraft wrote on 5/12/2007, 1:46 PM
only 2 seconds in two hours. I know this doesn't sound like much but most of you will understand.
Cooldraft wrote on 5/12/2007, 1:51 PM
Now that is one observation that I did not think about. Thinking about it, I just opened a project in Vegas and started assigning the audio tracks. I'll bet it is not the same. GOOD POINT!

Is there a way to precisely nudge the alignment with then num 4 & 6 keys?

edit: found an awesome way to do this.
Chienworks wrote on 5/12/2007, 2:03 PM
My technique for this is to find a spot near the beginning where i can sync the audio, then split the audio track at that point and delete the part before the split. That way, when i Ctrl-drag the end to get the end sync'd the beginning doesn't move. When i've got the speed right i'll drag the beginning, actually now that point where i split, back out to the left to fill in the audio prior to the split again. This way i don't have to keep continually fine tuning the beginning and speed over and over again.
riredale wrote on 5/12/2007, 2:46 PM
Cooldraft:

Okay, that's 1 frame for every 2 minutes of video.

On my Minidisc recorders, they drift to the extent of 1 frame for every 4.5 minutes, so your situation is similar. Very easy to adjust, and you might find that the drift is consistent, so you can automatically make the adjustment in the future for similar projects.