Generation loss with DVCProHD?

What kind of visual generation loss can I expect to see by going down 2-3 generations* in DVCProHD Quicktime files since I realize it's not a lossless format.

* ie using footage that has been gone thru 2-3 encode/decode cycles

Can you describe the "2-3 encode/decode cycles"?

Are you transcoding to a lossless format or another lossy format then back to DVCproHD?

One way to test (if you haven't resized or used filters) is to take the original and line it up in FCP (frame accurately) over the 3rd Gen and then use the Difference layer mode on the clip on Track 2.

Any difference will show up as colours and detail whereas any areas that are identical will show up black.

You can also do this with Photoshop CS5 by importing the Quicktime.



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The 2-3 encode cycles was outputting a full res DVCProHD Quicktime file from my FCP 6 timeline, then re-importing it into FCP, then repeat. The reason being that my project file was corrupted and that output file is now my only color corrected source to continue using in a new project file. Nothing was resized but filters were used. I do have the camera originals, so if there's a big image diff I could use those instead but would take a long time since it's a 90 min feature and we're short on time to deliver. Also the whole film would then have to be color timed all over again which isn't a real possibility due to budget and time constraints.

> Also the whole film would then have to be color timed all over again which isn't a real possibility
> due to budget and time constraints.

You did a full professional colour-time on a 90-minute feature, all done in Final Cut Pro, and you didn't do a single backup of the project file? And all your Autosave versions were also corrupt? Yipes. Somebody -- post-production supervisor, editor, whoever's in charge of post -- needs a massive kick in the behind.

I'd find it hard to believe you don't have even a pseudo-workable or incomplete project file lying around that you can use to restore at least most of your colour correction work. Do you have an experienced editor/troubleshooter working with you? The lack of backups, unfortunately, suggests to me that you don't...I think you should hire one for a day or two to look through your files. I could be wrong, but I think it's possible that you went straight to a "last-resort" measure before you exhausted all your possibilities of finishing your film properly.

If you already have a full-quality movie file, why would you re-import that into FCP anyway? Just go out straight to tape if that's where you're going. The same said file can be used for titles, audio mix, etc.


www.derekmok.com

derekmok Wrote:
-------------------------------------------------------
> > Also the whole film would then have to be color
> timed all over again which isn't a real
> possibility
> > due to budget and time constraints.
>
> You did a full professional colour-time on a
> 90-minute feature, all done in Final Cut Pro, and
> you didn't do a single backup of the project file?
> And all your Autosave versions were also corrupt?
> Yipes. Somebody -- post-production supervisor,
> editor, whoever's in charge of post -- needs a
> massive kick in the behind.
>
Haha Derek that would be me. The backup and autosave versions won't open either. Tried deleting all the render files, but still no go. Since I'm the sole person in post (besides sound/effects ppl), as well as director, co-writer/producer, etc think it'd be hard to kick myself The color time was done on a daVinci with layback to HDcamSR, not in FCP.

> I'd find it hard to believe you don't have even a
> pseudo-workable or incomplete project file lying
> around that you can use to restore at least most
> of your colour correction work. Do you have an
> experienced editor/troubleshooter working with
> you? The lack of backups, unfortunately, suggests
> to me that you don't...I think you should hire one
> for a day or two to look through your files. I
> could be wrong, but I think it's possible that you
> went straight to a "last-resort" measure before
> you exhausted all your possibilities of finishing
> your film properly.

> If you already have a full-quality movie file, why
> would you re-import that into FCP anyway? Just go
> out straight to tape if that's where you're going.
> The same said file can be used for titles, audio
> mix, etc.


I have the color timed master from this summer but have made many, many changes since then in that now corrupt project file. Basically what I need to know is whether it is worth my (very limited) time to recut the film from the CTM, or just import the latest DVCProHD QT output file that is down 2-3 gens* from the CTM and finish the titles, effects, etc from there in a new project file. Just using the CTM is not an option due to the changes made. Luckily we have the 5 reels of omf's so the audio post/mix isn't a problem besides the sound guys doing some conforming.

*All gens were DVCProHD to DVCProHD.

> I have the color timed master from this summer but have made many, many changes since
> then in that now corrupt project file.

Changes in editing? You colour-corrected before locking picture? Or you added filters?
Strange, but not unprecedented. But it's the same issue, which is why you don't have a viable backup this past summer.

If even properly backed-up project files won't open, then you have a different issue -- which is something wrong with either the media or your FCP software. For the former, you detach the media and open the project file. For the latter, you run diagnostics on the computer, reinstall FCP, and/or switch to another station. There are plenty of options for rescuing a project file that won't open. I'm not convinced you haven't exhausted them.

If your colour-corrected tape master was HDCam SR, why is your media in DVCPro HD again? Did you pay the money to master to HDCam SR, rent the deck to recapture into FCP, only to work at DVCPro HD quality? That seems bizarre to me given that your HDCam SR master would already consist of trimmed footage.

Your workflow doesn't make sense to me. It seems to me like you're doing things all over the place. Did you ever sit down with a post super, or editor (or even the post house) to figure out what your steps are before you spent all sorts of time, money and effort?


www.derekmok.com

Yes, I understand the workflow seems convoluted, but it's a micro budget art house film and we had a window of opportunity to color time this summer before we were done with editing, effects & sound...which is why I had to go back back to FCP and DVCProHD to finish. This is all being done on a G5 running FCP6, and don't have another station to switch to. So my question still is - what kind of hit are we taking going down multiple generations in DVCProHD? And is it worth it to spend the time saving a couple of gens by mainly using the CTM and doing fairly extensive re-edits? Or just go with the several gens down QT layoff which won't need much work.

I do appreciate the comments you and Ben have made, thanks!