Hello everyone,

We're currently working on an hd project on the Avid Media Composer 2.7.2

We have a 1080p/25 project and we did our offline on that project.  Right now, they are doing some effect shots on discreet inferno and I need to get them back to the avid.  Our edit is very complicated with a lot of split screens and promoted timewarps which the inferno operator needs to match manually by watching the offline.  We don't want to do that.

We did our offline from an hd cam onelight telecine.  We now have the final grade on an hd sr tape.  What we planned on doing is:  I give the inferno an edl with all the shots I need, they capture all the material from the hd sr tape, export a tga sequence for me, I import it into the avid with 1:1 resolution, put the shots manually back into the edit, (it's just a 30 sec commercial and I can manually conform very quickly) export a tga sequence of the finished edit back to the inferno and they lay it back to an hd sr master.  It all sounds right up to this point.

However, we tried a test on one of our shots and came up with a problem.  On the inferno, when we compared the original shot and the tga I exported, we saw that there is a very little difference between the images.  It's really very little but it's still there and that's unacceptable for us.

My import settings for the targa are:

Aspect Ratio, Pixel Aspect>  601/709, non-square

Color Levels:  RGB

Alpha:  ignore

My export settings for the targa are:  8 bit color depth with no compression.

I'm of course working on 1:1 mxf files and 1920/1080 aspect ratio. 

Any help is appreciated, thanks in advance.

How are you monitoring, thus comparing the shots?

Do you have the 1:1x option to import?  That's the 10-bit version of uncompressed, and might help.

And what kind of difference are you seeing?  Gamma?  Color shift?  What?

Thanks for the quick reply's.

We are comparing the shots on the inferno, using a difference matte filter and also our eyes.

I don't have the 1:1x option on import.  I have 1:1 mxf and 1:1 10b.  I tried it both ways without any difference.

It seems to have a bit of compression and a tiny change in the color, that is, it gets a tiny bit brighter.  They are not really noticable.  They become apparent when you zoom in and compare the two shots.

Some new info:

The targa sequence exported by the inferno is about 600 mb and the targa exported by the avid is about 400 mb.  So can it be that avid somehow compresses the targa on export?  (Although I have compression unchecked on the export setting)

We also tried exporting a tiff from the avid with exactly the same problem.

Also we re-imported the targa sequence that was exported from the inferno back into the inferno and compared the results and saw no difference between the images.  So we know the problem isn't on the import/export of the inferno.

Our technical manager guesses it's just because of "the difference in the way the two machines work with images."  Does this sound plausable to anyone?

Thanks again.

Open a Targa file from each system in Photoshop. See if you can find any difference in the file format (bit rate, color depth, etc).

I think the format of all the Avid's codecs is YUV. There are options for colrospace conversion available via console in Avid. And Targa is RGB so the colorspace conversion must be done which can't leave the colors untouched. Targa can be compressed losslessly only so it's not the problem.

PP