Yes, they will play in sync. I regularly turn off quantize to frames when working with audio tracks. Hopefully you did all your video track editing with the "quantize to frames" function ON, editing with it off can cause big problems.

Don't quite get you, John - I just said I had to cut, copy and paste both video and audio events with frame quantization off, in order to be able to perfectly synchronize with the master audio compiled in an audio editor (outside Vegas), with a millisecond accuracy...

What sort of problems should I expect? While still in my Vegas project, they are all in sync...

You don't need millisecond accuracy in this case.
Keep your vision on frame boundaries by having QTF ON.
Then switch it Off to sync the music.
As you're not mixing the new audio with the old then it only has to look like it's in sync. +/- 10mS is close enough. Remember sound travels slowly.

Bob.

You simply can't edit video with millisecond accuracy. You CAN edit audio with 1/48000th second (.002 millisecond) accuracy. You can only edit video on frame or field increments, in NTSC-land this means 33 or 16.67 millisecond increments. (PAL would be 40 or 20 milliseconds.) If you edited the video with quantize turned off (which you did), Vegas will most likely render it on field boundaries, which means 16.67 millisecond (or 20 ms for PAL) accuracy. That's the best you can hope for.

Also keep in mind that only one audio sample out of 1602 is actually in sync with the frame. A frame lasts for 1602 samples, but is an instantaneous picture during only one of them. The rest of the samples come before or after the image. That means that on average, sync is off by 801 samples at any given moment. That's about 16.7ms. No matter how carefully and exactly you line up the sync you physically can't get any closer than that.

There is never a need to cut video at increments smaller than frames; it just doesn't accomplish anything. An since nothing smaller than frames matters, there's no reason to cut anywhere but on frame boundaries.

Thanks guys; this is more or less the kind of answers I was expecting. However, in this particular case, I CAN see/hear a delay as short as some 7 msec when the guitarist nail is plucking a string...

This is why I'd turn both quantize to frames AND snapping off, and while still in the project (zoomed deeply in), I am able to synchronize it perfectly. As stated above, down to some 5-7 milliseconds!

The only thing that worries me is what surprises I'm facing after the final render. If Vegas just snaps the video back to where it belongs in the PAL video world (i.e. to the frame boundaries), it's probably OK; but is it possible that the discrepancies I have now in the project will accumulate somehow, and create much longer delays?

There is never a need to cut video at increments smaller than frames; it just doesn't accomplish anything. An since nothing smaller than frames matters, there's no reason to cut anywhere but on frame boundaries

I absolutely agree, and am aware of it. The thing is that cutting audio with much greater accuracy, I was cutting it along with its associated video, so I couldn't obey this rule. When I pasted the chunks into the new project, I re-created the audio perfectly (i.e. with the millisecond accuracy); I then deleted the cut&pasted audio, leaving just the master audio track to which I was synchronizing, and the video events - obviously NOT starting/ending at frame boundaries.

Will I get away with it?

I think you're obsessing over timing that, in the real world, won't make any difference whatsoever. Sound travels through air at approximately 1.129 feet per millisecond (.344 meters per second) at 70 degrees F (or 21 C.) If you're at a concert, 50 feet from the stage, you will hear ALL the sound 56 milliseconds LATER than what you are seeing. We're all used to this and it bothers none of us. NOTHING is ever synchronized perfectly. If you're standing 5 feet away from me, you will hear my voice 5.6 milliseconds AFTER you see my lips move. Now, if you hear the audio BEFORE you see the event, that will drive our brains NUTS.

The only way you're going to find out is to render it.

I can't say for certain what could go wrong however many problems that people have had over the years seem to relate to editing vision with QTF Off.
I'm not too convinced either about the wisdom of editing at the field level, you'd break the cadence and possibly cause all manner of problems.

Far, far safer to leave the vision as it should be and slip / stretch the audio. Your problems started at the shoot using non synced clocks, that has implications for many things and the problem gets worse in a multicam shoot because the shutters are not in sync. I've had this exact problem, you cut between two cameras and you get a jump in the action or you dissolve between them and it's very obvious something is wrong like the dancers arms are in different positions.

Bob.

Yes, human brain is trained to receive sound after the vision, therefore when you're listening to a guitarist from some distance, you don't even notice it.

However, when you're watching his right hand blown up on the big screen, and its movements are not perfectly synchronized with the audio you hear, now that's another story. This is why I synchronized so precisely - otherwise I could see the delays!

Nevertheless:

The only way you're going to find out is to render it.

Amen to that.

Yes, of course you want the audio synchronized as close as possible and you can get extremely close with Vegas by slipping or stretching the audio. The point is that your video cuts MUST happen on frame boundaries, so you MUST leave quantize to frames ON when editing the video track. You should never slip the video in less than frame increments, only slip or stretch the audio to match the video.

And that's why you should use genlocked cameras for such projects.

The only thing that might happen is a black frame at an event boundary. This could happen if your video got moved by 3/4 of a frame (with Quantize turned off). I'm not sure at what point Vegas doesn't use a frame.

To figure out if you have a problem, just use one of the keyboard shortcuts to go to the end of each video event. If the display shows some video, go to the next event. If it shows black, make sure Quantize is turned on, and then move the edge of both events.

if you are really obsessive, there is a Quantize to Frames script which will re-quantize each event so that every video event ends on a project frame boundary. Quite frankly, however, if you don't have any problems (and you probably don't) you'll probably end up causing more problems with this script. I'd only run it if you found lots of black frames.

John,
if by "going to the end of each video event" you mean using Ctrl+Alt+Left/Right Arrow (to move left/right to event edit points) - then no, I don't see any black frames.

So if such black frames are the only possible consequences of my adopted editing method, I hope I got away with that this time.

Nevertheless, next time my sound engineer will have to comply to my video editing ways and limitations - and not the other way around.

Many thanks to all.

**So if such black frames are the only possible consequences of my adopted editing method, I hope I got away with that this time.**

Another, unacceptable consequence of not cutting to frame boundaries, at least in earlier versions of Vegas, was the random frame bug, where a frame from elsewhere in the project would flash in the gap between the non-butted frames, during both preview and render. I haven't tried to replicate it in V8, because my habit now is to do all of my video cuts in QTF, then turn it off when working with audio tracks other than the reference audio track.

musicvid,

Thanks for that input - please elaborate: did it happen when still inside the Vegas project (which doesn't happen here), or can it also show its ugly face AFTER rendering out?