sync sound while previewing to external monitor

[Josh Bass]

I basically posted this in another forum, but I'm trying again here.

I use Vegas 6, and I have an NTSC monitor. I'd like to be able to watch the video on the external monitor, and listen to the sound at the same time, the way you can in a "real" edit suite. However, my sound is always out of sync with the video.

Apparently, you can't send the sound through the firewire, so, has anyone found a way around this?

Here's the other thread, for reference:

http://www.dvinfo.net/conf/showthrea...145#post611145

[Edward Troxel]

Plain and simply: When using External Preview, the sound will still come from the computer's speakers.

Now, there IS an adjustment in the preferences to allow for latency. Have you tried adjusting that? Options - Preference - Preview Device tab. There's a slider called "Sync Offset". Adjust that as needed. The default value of "4" has always been correct on my systems.

[Josh Bass]

So this'll fix the sync issue?


Usually, if I start playing a clip, it'll be in sync for a few seconds, and then slowly drift farther and farther.

I thought perhaps there was a more elaborate, if a little more expensive, workaround.

I'll try the latency adjustment, though.

[Edward Troxel]

If it starts in sync and slowly drifts away - that's an entirely different issue.

[Josh Bass]

It's like the sync is accidental, and just happens to work for a few seconds.

[Mike Kujbida]

What's your preview window set to?
Mine is usually set to Preview/Auto and I don't have any sync problems unless I really load up on the FX.
hen again, I expect that so I do a RAM render in those cases.
BTW, this is with a P4 3.4 HT machine.

[Josh Bass]

I can set it to whatever, depends what I'm looking at. If it's unaltered footage, I should be able to look at it "best full", right? At least preview full, which looks almost identical.

It's not worth getting a faster PC for, but if there's a piece of gear I can buy, or something, that's different.

[Steve Leverich]

Josh, this problem is usually caused by your computer's sound card not having the exact same clock rate as was recorded by your camera - as the tape progresses, the drift becomes larger. A real PITA to be sure...

The simplest way around this is to get one of the Canopus boxes - the least expensive one that solves this problem is the ADVC-110

http://www.canopus.com/products/ADVC110/index.php

Check out the section titled

Locked/Unlocked Audio Support (about halfway down the page)

I have two of their units, the ADVC-300 and the TwinPact100 - you won't be able to pry either one of them from my cold, dead fingers :=)

HTH... Steve

[Josh Bass]

Are those boxes what the pros use?


Anyway, I tried offsetting the sync to 8 frames, and it seems to have done it. I watched for several minutes at a time, and I can't see a drift. I swear I've tried it before and not had success, which is why I posted, but it seems to work.

I can't really tell any difference between 7 frames or 8 offset, but 4 is wrong and 12 is wrong, it's somewhere in there.

[Edward Troxel]

If it's consistently off a set amount, that setting will generally fix it (which is why I originally recommended it). If it drifts over time, that setting will have no effect.

[Josh Bass]

It seems to work, so far. I watched for a few minutes. It takes a matter of seconds when it drifts.

[Steve Leverich]

"Are those boxes what the pros use?"

Depends on whether you mean "I'm paying for everything out of my pocket" kind of pro, or the "I work for NBC and use THEIR budget" kind of pro - The parent company, Grass Valley Group, is their broadcast level pro gear line and they have been considered pro since my days in the '70's in broadcast video - but that gear is overkill and overpriced if you're on a realistic budget. The Canopus line is more of a "bridge" between consumer, pro-sumer, and low end broadcast stuff.

I got the two boxes I use because both provide color bars and video proc amps/TBC's at a price (around $500 each) I could handle - just a single test generator from Tektronix to do color bars and a few other signals, and also provide stable video blackburst, runs several thousand dollars. Not an option these days, for me anyway - my next acquisition is at least one of the Canon XH-A1's, preferably two...

Your problem may be fixed by changing the offset, but you won't know for SURE til you run the entire project without interruption from beginning to end, and preferably with your computer at two different temperatures for each of two runs - included sound cards for most computers are a joke if you're serious about audio, and their clock speeds (the ones that control sample rate) may drift over time and temperature.

IF you're NOT lucky, you may have just found a combination of temperature and offset that SEEMS like you solved the problem; if so, only the above test will tell you which it is.

IF you ARE lucky, you're DONE - but depending on what you offer for video services, you may still want to look at one of the mid-level Canopus offerings - for example, when I convert VHS to DVD for people, most of the time I play the tape on an editing deck synced to incoming black burst (video sync without a picture, or you can substitute a color bar test signal from either of the boxes I have), then take the processed output from the Canopus' firewire port and capture that for editing/cleanup. The end result is difficult to tell from directly captured DV unless you really look close.

Hopefully you ARE lucky, and offset was your only problem - but I'd still keep the Canopus line in mind, you may find that several of those capabilities will enhance your operation... Steve

[Josh Bass]

My unscientific test of whether I'd solved the issue was to watch the timeline on the external monitor, and then watch it from the preview monitor in Vegas, and see if the edits seemed like they were in the same place, and not a few frames apart. So far, seems fine.

If that A/D converter also solves the clock speed issue with the sound card, I may consider getting it, but if it's just for A/D conversion, I don't really need one right now.

As for the services I offer, I only do editing veeeeeeeeery occasionally for other people. The stuff I use it for the most is my own projects, but it'd still be nice to edit and not have to view the video in a 3.5" window on the screen.

[Steve Leverich]

The Canopus boxes vary in features quite a bit, also in price - here's a good page from one of our sponsors that spells things out pretty well

http://www.videoguys.com/ADVC.html

If you read the blurb on the 300, you'll see why that was the first one I got - the TwinPact100 I added later, in anticipation of more training video projects that will likely need the specific talents of that box.

I love having the external preview setup, the 13" broadcast trinitron is my color standard, then the composite signal loops thru that and into a 24" Toshiba TV sitting about 3 feet from my face (along with 3 19" LCD's) - Vegas is so much cooler when you can move all the tabs to a second monitor, leaving the main one for just the timeline and transport, The third LCD gets the virtual mixer for my firewire audio interface, plus a window for Word (scripts for V/O) - so far, it's all working really well for a temporary setup and it's giving me ideas for a more permanent editing room.

Sorry, 'nuff rambling for now, hopefully your sync offset change solves all your problems... Steve

[Josh Bass]

Thanks, but that sounds a bit overkill-y, the multimonitor setup. So far, the offset seems to be working. If not, I'll explore other options.