DV-AVI Undamaged Block Bypass

[Guest]

I'm trying to use After Effects to "inpaint" a corrupted frame from a MiniDV tape, by using good picture from the preceding and succeeding frames. It looks good on the stage, but when I render it and put the newly painted blocks into the original video (i.e. replace the original, corrupted 80B blocks with the new ones from AE), I'm running into a bit of an issue with the DV overflow scheme. After Effects is rereading and rewriting the affected frame, and it seems to be changing around the overflow data such that it doesn't match that of the original video, so the newly fixed blocks cannot be copied into the original video without introducing more noise.

Is there a way in After Effects to "render" unaffected blocks exactly as they are written in the source file and generate the new blocks from that? So that the program uses the existing overflow scheme in the source video?

[Rick Gerard]

The technique used to fix corrupted frames or "inpaint" for folks that don't know what that means, depends on the shot, the format, and the technique. 

It sounds to me like you have some compressed DV footage that originated on a DV tape that you somehow turned into a video file that AE can read. The very first thing I would do would be to transcode the original DV footage to an image sequence so you had as much information as possible available in every frame. 

Then, the technique to repair the glitches depends entirely on the footage. I have no idea what kind of workflow you are using so I'm not going to be of much help. Give us some workflow details and some screenshots that show us what you are doing (uu + PrintScreen + paste or drag to the forum) and maybe we can help. 

[Guest]

AE can read the DV-AVI file captured from the tape.

So, here's the original image with the corruption:

Original Image to be Inpainted

It is in the bottom-right corner.

So first I removed the corrupted blocks:

Corrupted Blocks Removed

Then I used the preceding and succeeding frames (with masks) to "paint" the missing parts of the image:

The painting mask, shown without the original good data.

Here's what the final product looks like:

Final Inpainted Image

Looks good from a distance. But that checkerboarding pattern you see by the wheel of the car? When I put the newly inpainted blocks into the original video file with a hex editor, more of that appears, because the DV overflow scheme is different on the saved file. I need AE to save my file using the original file's overflow scheme.

[Andrew Yoole]

I completely agree with Rick that you should transcode the DV material to an intermediate format before using it in After Effects.  DV compression is an unwieldy beast, and it's common to see corrupt files decode with visual differences on each pass.  By transcoding you'll at least be working with consistent visual errors.

[Dave Merchant]

This isn't a question about frame editing at all - you've successfully filled in the bad data on your corrupted frame - but you are asking After Effects to then render out something which you can hex-edit back into the original DV data file. After Effects was never designed to do that, and I cannot see why you would possibly want to. Just render the whole sequence to a new file!

[Guest]

Bingo.

I want to be able to retain the undamaged blocks as well as the date/time. But I could just hex-edit all of the video blocks saved by AE into the original DV data file, couldn't I? As opposed to just the damaged ones.

So, how do I set up AE to render the new DV file such that the good blocks look as identical as possible to the originals?

[Rick Gerard]

Fixing the hex in a file is not going to be as efficient as just compositing a repair. None of it is going to be very easy. Rendering DV footage to a suitable production format is going to be a lot better than leaving it in a DV file. If you have hundreds of frames with hundreds of blocks of bad data you are looking at a real mess.

[Dave Merchant]

You can't "set up" After Effects or Media Encoder to do what you want, they were never designed for such an obscure workflow and so there is no access to the low-level operation of the output codecs. You still haven't explained why you want to do a bitwise swap inside the original file instead of just rendering out and using a brand new one. The only time I can recall seeing this done was someone trying to create fake evidence.

[Guest]

I want to be able to print it back to MiniDV, and have a perfect "master copy" of the video.

[Rick Gerard]

Just output a rendered file to mini DV. That's not a very stable storage platform and I can't remember when I last saw a DV deck that was still working. Personally, I would prefer a digital file backed up on a hard drive. No chance of accidental damage from just playing the tape, magnetic print-through, or any of the dozens of other things that can destroy magnetic tape recordings.

[Andrew Yoole]

Without wishing to labour the point, I'm with Rick.  I can't think of a single reason to archive something to DV tape in this age of cheap digital storage.