Another possible way to work with Gearshift?

Laurence wrote on 2/18/2006, 7:29 AM

It just occurred to me this morning as I was setting up another Gearshift proxy render that there might be an easier way to do this:

How about capturing the video twice, once with HDV Split as m2t files and once with Vegas as camera downconverted SD avi files. The files should be exactly the same thing video in both formats. Then all you would need to do is rename the avi files with a GSPROXY_ prefix and switch back and forth between them in the usual way using Gearshift. It seems to me this would be a whole lot quicker: an extra hour per tape instead of a six or seven hour render. I'll try it tonight with today's footage and post whether or not it works here.

Comments

JohnnyRoy wrote on 2/18/2006, 9:06 AM

To my knowledge it is impossible to get the capture to be the same each time (i.e., frame accurate). That’s why we wrote GearShift in the first place. Otherwise you could just capture downconverted DV and edit your project in SD and then re-capture the full M2T file and substitute at render. This was the question everyone was asking in the beginning and the answer is, you can’t capture the same footage twice in different formats and be frame accurate. So GearShift was born.

~jr

Laurence wrote on 2/18/2006, 6:04 PM

Thanks. I'm a little slow I suppose.

farss wrote on 2/18/2006, 9:29 PM

Possible stupid question here. I can understand how the batch capture may not be frame accurate however for this to really fail the TC would have to be different. I'm just curious, is the problem that the HDV Vs DV outputs from the HDV decks don't have the exact same TC?
If that's the case then there's a few non Vegas workflows that might be a bit suspect.

Bob.

Spot|DSE wrote on 2/18/2006, 10:00 PM

It's that there is no frame accuracy with HDV that causes the problem. The T/C is the same, but hitting a specific frame currently seems to not be possible. We're told by manufacturers (haven't really dug deeply into this) that the way the T/C is embedded in HDV causes this. I struggle with that, but haven't assigned it enough importance yet to really dig in to it.

Laurence wrote on 2/18/2006, 10:07 PM

Just curious: it seems to me then that the standard way of logging a capture and doing a project and using the original tape and capture log as a backup is really not all that useful with HDV anymore. Is that the case?

farss wrote on 2/19/2006, 3:36 AM

That's pretty much what I was getting at.

The traditional way of working is to log and batch capture a low res proxy as an 'offline', then take that project into an 'online' suite. The tapes are then recaptured at full res and the whole thing conformed.

What I don't get (and I'm really grappling with this in an area other than HDV) is why does the 'online' capture have to be frame accurate? Why not just capture with handles, firstly that'd make it easier if you wanted to make minor changes in the online suite and secondly avoid the problem if there's a few frames offset in the capture.

I can understand this is an issue in a linear tape to tape on line system but why in a digital workflow.

Bob.

JohnnyRoy wrote on 2/19/2006, 7:12 AM

One issue is the way that Vegas handles media on the timeline. Timecode is irrelevant. Events on the timeline come from real physical files in the filesystem. When you trim the event, you are subtracting frames relative to the beginning of the physical file! If you recapture the file and it doesn’t start at the exact same frame, then the offset into the event in Vegas will place you on the wrong frame. So as far as Vegas is concerned, it has nothing to do with timecode. You are not editing by timecode. You are editing by frames from the beginning of the file.

If you had a way to capture downconverted DV and HDV that was frame accurate, then all this would work. So it’s the capture utility that would need this capability. Unfortunately, Vegas uses two different capture utilities for DV and HDV so I don’t see how a log from one could be even used in the other.

Alternately, if Vegas used the timecode in the file for editing, then it wouldn’t matter if your captures were frame accurate, as long as that timecode existed in the file. But Vegas doesn’t work this way (and it would require all media to have timecode or be assigned timecode if it was missing).

~jr

farss wrote on 2/19/2006, 1:08 PM

Thanks jr!
I'd kind of worked out the issue with Vegas using two ways to capture after I'd posted my question and I can see an issue with HDV, the decks simply cannot send you vision that starts in the middle of a GOP. What I didn't realise is that Vegas doesn't use TC to that extent, yikes, that's a worry.

Bob.