Dropped MiniDV audio means video dropped too?

AVERAGEJOE wrote on 8/10/2004, 7:34 PM
I am trying to sync DAT audio to MiniDV video....however I am having sync issues about 45 minutes out....I have noticed there are occasional drop-outs/deadspots/whatever in the audio of the MiniDV track, but I still match both DAT and MiniDV audio up 100%..are those MiniDV audio dropouts also meaning 'dropped' frames in the video even though I can't see them and didn't drop any capturing them???
That could be the reason for the sync issues?

Ruler has been set for drop and non-drop, no luck on either

Comments

B.Verlik wrote on 8/10/2004, 8:33 PM
This is hard to answer as I've never worked with a MiniDV video cam. It should be pretty much the same as a regular size cam and I've never had audio drop outs, so this is puzzling. My only suggestion, if you aren't seeing video drop-outs, is that somehow your cam just goes out of sync as soon as the audio disappears. My only remedy is to 'Time-stretch' the video (shorter or longer) to match the sound until you're on level ground again. It's a pain in the butt, but it's easier than it sounds. You may have dropped a few frames or it just gets wacky without the audio. Could it have been a place where the camera was 'Shaken' that you lose the audio? That's usually where I drop frames with my Hi-8 cam. (This is what's time consuming for me is to fix those drop-outs.) Just 'chop' the areas right around where the sound is missing and 'Time-stretch or compress' to fit again. (click on the track and then hold down Ctrl key and when you see a wavy line appear then shorten or lengthen until sync'd. Zoom in if you have to.)
riredale wrote on 8/11/2004, 11:00 AM
So as I understand it, your DAT audio track and the miniDV audio track sync up perfectly to the end of the 60-minute tape, but about 45 minutes in you get some glitches in the miniDV audio, right? That would imply to me that the recording process in the camera is continuous, but that either some part of the audio circuitry dropped the ball or there was a bad spot on the tape. Is the dropout repeatable with that tape? If so, I would assume the tape has a problem.

Using a drop-versus-nondrop time code has nothing to do with what's on the tape. It simply makes the numbers at the top of the Vegas timeline match more closely with the actual elapsed time of the event.
AVERAGEJOE wrote on 8/11/2004, 2:04 PM
I start losing sync around 45 minutes, but the entire clip was 60 minutes. 'd say by the end a half-second off.

Funny part is that the MPEG2 I play in Windows Media Player is perfect sync on the PC, it's just that when DVDA breaks it off into AC3 it gets screwy.
B.Verlik wrote on 8/11/2004, 9:29 PM
Try this. When you go to render the mpg. using the exact same timeline (looped area), first render the .ac3. Then render the mpg WITHOUT audio ('Custom' template,Audio tab, uncheck audio stream, give it a name and save). When you go to make the DVD. You can watch the preview and listen at same time in DVDA. Be sure to write down the exact points, right down to the frame, where video begins and ends (in Vegas editing looped area) so if render doesn't take, you can re-do it again. If you put the mpg and ac3 in the same file, DVDA will bring them both in. Rendering audio in ac3, allows you more options plus you can preview in DVDA to make sure it works before burning. I've had to re-make ac3s, due to errors and you can delete either audio or video in DVDA and re-do if needed. DVDA will no longer have to make a new ac3 when you make the DVD and save you the time you used to make it earlier. (which is just a few minutes) I believe you need two/three seconds of silence on either side of the video to get a good ac3 file, when you make it separately. I insert a 3 second 'Empty Event' on both sides when rendering ac3 files. (Dolby labs uses this silence to automatically adjust ac3) I have to admit, I still don't understant how your timing went off in the making of a DVD, if it worked otherwise. Didn't it work in the DVDA preview? Before it made it's own ac3 file?
B.Verlik wrote on 8/12/2004, 1:22 PM
One last thing concerning this, you never mentioned how many audio drop outs you had but if you were only off by a half second at the end, my guess is that you did lose one or two frames whenever you lost the audio. So by the end you had about 15 frames missing. Not necessarily noticable while watching if only 1or 2 was lost at each drop out.