Friday, January 2, 2015

Why does Adobe Premiere Pro modify original footage/asset files

The following scenario was featured over on StackExchange.

Background:
  1. A colleague had given me a large 33Gb .mov for use in a project, I put this file on a backup drive.
  2. I made an identical copy of this 33Gb .mov file and placed it in a folder that I'd use to work on a Premiere Pro Project.
  3. I ran Adobe Premiere Pro CS6 and dragged in the 33Gb .mov file into the Sequence (imported it)
  4. Premiere Pro CS6 started conforming the file.
  5. After it had finished, I noticed that it's Modified Date was just now i.e different to the Modified Date on the original copy of the file on the backup drive (see step 1)
  6. I ran a BeyondCompare check between the .mov file on the backup drive (see step 1) and the one that the Premiere Pro project was using (step 2, 3) and Beyond Compare reported they were different.
I had initially thought it was unrelated file corruption of some kind, but I have checked this several times and got the same outcome, so it's definitely Premiere Pro deliberately modifying the file.

So I am puzzled: these are supposed to be the same file.

Why would there be a need for Adobe Premiere Pro to modify the footage? What does it do to the file? Would it not be better to create a separate file if necessary?

The answer to the user's question is featured here:

"It's all about this setting, "Write XMP ID To Files On Import" - which confirms that Adobe Premiere Pro is deliberately modifying the .mov file."

These posts give some background as to why having this setting enabled would be beneficial: one benefit being to be able to skip conforming files by matching the conformed file with the original using the embedded XMP tag:

http://helpx.adobe.com/premiere-pro/using/preferences.html#WSE3BD4A43-7022-4fe6-97F5-95313935347B

http://www.dvinfo.net/forum/adobe-creative-suite/498627-why-premiere-modifying-video-files.html

https://forums.creativecow.net/thread/205/876064

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Can you imagine what would happen on the witness stand if you didn't know this was happening to your files, and the opposing attorney asked you a series of very specific questions about your Premiere Pro (of Avid) work flow? OTS software does a lot of stuff to your files without telling you. That's the peril in using it for your forensic science work. It's yet another reason I've ditched the commercial editors in favor of software purpose built for our industry.

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