[Tig] ASC CDL in the DPX header

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Wed Oct 7 21:11:51 BST 2009

On Wed, 7 Oct 2009, Jeff Christopherson wrote:
> I had always thought it a good idea that every system processing a DPX image 
> would somehow make a record of it in the header, appending it to any metadata 
> concerning previous processing. Something analogous to the papers that travel 
> in film cans.
> The data need not be great - just a tag with the application name, version, 
> some text about the manipulations done and the date. 1KB per process would be 
> overkill, I think. The file spec reserves 1MB of header space for "User 
> defined data" and some other header sections have space "reserved for future 
> use". While a SMPTE revision would be great, this kind of record keeping is 
> currently possible if there was cooperation in the industry. In fact, the 
> file spec states that the user defined data can be used for "... processing 
> logs, etc.".

This seems like an interesting idea.  The required user space should 
be reserved in advance so that it is still possible to update the user 
space or pixels without re-writing the whole file.  Of course, a log 
file could be maintained alongside the DPX file.

There seems to be considerable usage of the user area already.  Some 
people are putting audio in there.  Others are adding a complex 
metadata chunk which is capable of storing arbitrary metadata.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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