Encrypted DCP Technical Preview

[Paul Finn]

I seem to remember that early in the digital cinema evolution the standards allowed for a technical preview capability (picture, sound, masking, etc.) by running a few minutes of an encrypted feature before the "key" arrived and was active. Is this capability still available today and if so, what are the method, limits and restrictions on its use?

Thank you, Paul Finn

[James Gardiner]

I have never seen or heard mention of such capability in the standards body. From my understanding, it is not possible based on the DCI implementations. (Interop or SMPTE)

For example, you would need to make a portion of the assets non encrypted. That's not possible based on the implementation.
They could send a completely different CPL/assets that only show the test portion of the film, but that defeats the purpose as you want to test it plays the FILM assets.

[Jose Angel Velasco]

On film festivals, I request an additional KDM for test purposes, that opens the DCP in a specific test day.

[Ryan Gallagher]

Yeah festival mode is just to have multiple keys, or insist on keys that cover the festival (if the fest has enough pull for that). Certainly makes life easier in the booth when the time windows are not a concern.

[Jim Cassedy]

I second what everyone else has said. However sometimes for some festival shows, and
for a major advance preview screening a couple of months ago, I was able to get a 'test key'
that opened for only 30min early in the morning the day before the scheduled event.
This required intervention by the director himself, who said either he or a representative
would be there at the assigned time to do a quick QC. He seemed most concerned about
the audio levels and how it was going to sound in our large auditorium So, I was there at
the assigned time,( 7am ) but nobody else showed up. I waited about 10min and then QC'd
various parts of the flick for the remaining 20min by myself. It kinda pithed me off, because
I had worked a late shift the night before and would have preferred sleeping in a bit the next
morning. When I was finally in contact with the distributor later that morning, no explanation
was given as to why nobody but me showed up, and all the director said to me before the
preview, was "so, how did it sound yesterday?" Maybe it's just me, but I felt like I'd been
jerked around a bit.

[Ryan Gallagher]

I second what everyone else has said. However sometimes for some festival shows, and
for a major advance preview screening a couple of months ago, I was able to get a 'test key'
that opened for only 30min early in the morning the day before the scheduled event.
This required intervention by the director himself, who said either he or a representative
would be there at the assigned time to do a quick QC. He seemed most concerned about
the audio levels and how it was going to sound in our large auditorium So, I was there at
the assigned time,( 7am ) but nobody else showed up. I waited about 10min and then QC'd
various parts of the flick for the remaining 20min by myself. It kinda pithed me off, because
I had worked a late shift the night before and would have preferred sleeping in a bit the next
morning. When I was finally in contact with the distributor later that morning, no explanation
was given as to why nobody but me showed up, and all the director said to me before the
preview, was "so, how did it sound yesterday?" Maybe it's just me, but I felt like I'd been
jerked around a bit.

They probably never intended to be there the day before, but that was the assurance the studio needed to get the key issued.

One trick I use is to have a host of test pattern DCPs I threw together myself specifically to be a target for adjusting our masking and screen files. If I end up with studio generated ones too I never delete those either, and that combined set covers almost all aspect scenarios.

This one is from my 1080p Alt source set (2K ones are not handy on this computer), and the forum is gonna resize it, but you get the idea,.red being what you don't want to see. I've got even goofier ones, like phone portrait mode aspect ratios (thankfully never deployed yet).
1080p Alternative Aspects 100.png

Presuming I actually "knew" the proper feature aspect, even without a key, I can nail masking. Audio is a bit trickier but at least generally easier to adjust on the fly, assuming all channels are showing up and mapped properly.

The fact my aspect test DCPs are venue branded and clearly labeled on screen also seems to inspire a bit of confidence among the creatives if it is the first thing that greets them, and it matches their film aspect!

Because we prefer to do a bit of keystone correction crop here due to our booth angle, I really want to know the exact ratio, otherwise weird partial crops become visible near the edges if you are in the wrong aspect and masking. You can always be in wider setting, but draw attention to our keystone and/or blank screen. Yuck.

[Carsten Kurz]

It is possible and fully DCI/SMPTE compliant to create DCPs that are only partially encrypted. Encryption takes place on the asset and reel level, and every single asset may or may not be encrypted, that is fully DCI and SMPTE compliant. I regularly see encrypted mainstream DCPs that have a local distributor logo or a final dubbing artists name card added unencrypted as a separate short reel. Also, for a while and even sometimes today, encrypted SMPTE DCPs had just their subtitle or CC assets unencrypted because some servers were not able to decrypt caption files.

The trouble however is - once even the smallest part/reel of a CPL is encrypted, no server will attempt to play it if not all necessary keys are available the moment you try to hit play. So it's useless even if e.g. the first 10min would be an unencrypted audio/video reel.

Technically, a server is never able to play encrypted parts of a DCP when the keys are not available. The KDM does not just instruct or allow the server to play encrypted content, it carries with it the necessary data to decrypt the content. If that key/data is not available, it is technically impossible to decrypt or play.