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Cineon Forum Index Discussions / Questions cin file size changed on ouput from inferno
Author cin file size changed on ouput from inferno
meeotch


Joined: Mar 18, 2008
Posts: 2
Posted: 2008-03-18 16:26   
I've got some files that have been imported to Inferno, and written back out again, with no changes. The file size, unfortunately, did change - from 12773376 bytes to 12748800.

"cmp" and "diff" say that the files are different, starting right at the beginning (so it's not just a blocksize issue) - but I'm assuming it's just header info that's been altered, as a difference matte shows no alteration to the image data.

How can I compare these two files and ignore header data, to see if the image data is bit-for-bit identical? Also, is there a small utility (preferably free) that will let me inspect the headers to see what's changed?

Alternatively - is there a python library that will read/write cineons?


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David Hodson


Joined: Nov 27, 2004
Posts: 15
Posted: 2008-03-20 05:09   
The difference may well be in the header, as you suggest - the original files probably contain a thumbnail image in the User Data area, which has been stripped off when exported. The file format spec is right on this site, at: http://www.cineon.com/ff_draft.php

ImageMagick is a free and very comprehensive software package, which can almost certainly (although I haven't checked) [a] read Cineon files, [b] compare image data, and [c] be used from Python.


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meeotch


Joined: Mar 18, 2008
Posts: 2
Posted: 2008-03-20 06:39   
Thanks - I actually did find that document, and by skipping past the header (2048 bytes in the pre-inferno file, and 26624 in the post-inferno file), it appears that the image data is the same.

The inferno may be adding a thumbnail, rather than subtracting one - a header difference of 24k seems rather large. It also seems to be killing the "date" field, and who knows what else. Pretty irritating, given that the original files came from a Lustre (another Discreet product).

I guess the next step it to find a good graphical binary comparator, and try to figure out what's been changed. Sigh.


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