If you ever plan to screen a film or video in a cinema, there’s no escaping it: the DCP.
Simply put, the DCP is the digital successor to what used to be 35mm film. Mention it to anyone who’s ever stepped inside a projection booth, and they’ll likely know exactly what a DCP is and how it works. But let’s be honest, that’s a pretty small and select group of people. So, for everyone who finds themselves dealing with this mysterious cinema format without really knowing what it is:
Here's a short introduction by Frank van der Horst from Filmfetch.
DCP? Sounds like an abbreviation.
You’re absolutely right. It stands for Digital Cinema Package. And that last word, package, is key. When we talk about a DCP, it might sound like we’re referring to a single file, but in fact, it’s a bundle of digital files. If you ever find yourself the proud owner of a DCP, you’ll be looking at a folder containing several different files.
But I thought it was something physical, like a hard drive?
That’s a common misconception. In the past, if you asked for a DCP, someone would probably hand you a hard drive. But what actually matters are the files on that drive. And even those drives are now mostly a thing of the past. Today, DCPs are usually transferred over the Internet.
So it’s a set of files. Are they always the same?
The correct answer: yes and no.
That’s not very helpful... can you explain?
It’s a bit technical, but that’s part of the beauty of the DCP system. Broadly speaking, DCP files fall into two categories:
Metadata files that describe the package itself - what’s inside, and where everything can be found. In other words, it’s a kind of table of contents.
The content itself - the actual media files, such as the video track, the audio track, and the playlist that links them together.
Here’s the clever part: there can be multiple versions of these components within a single DCP and sometimes they’re all used, sometimes only a few.
Okay, now you’ve lost me.
Let’s take a step back. One of the biggest challenges in modern cinema is that many different versions of the same film need to be created. Different languages, subtitles, formats, and sound systems. A major blockbuster, for example, might be released in standard format, IMAX, and Dolby Atmos sound. If each version required a completely separate film file, you’d end up producing and sending hundreds of versions. Time-consuming, complicated, and expensive.
That’s where the DCP comes in. Think of a DCP as a box of LEGO. Inside the box are all the pieces: the video file, the audio file, and the subtitle files. Using these same “bricks” (and occasionally some extra ones), you can build different “film versions”, depending on how you combine the parts.
Each of these combinations is called a composition, and the “instruction manual” for building it is the Composition Playlist, or CPL. The CPL tells the playback system which video, audio, and subtitle files to use for that particular version.
That means you can include, say, one video file and one audio file in your DCP, plus ten subtitle files and ten CPLs, allowing you to serve ten language regions with a single DCP.
Handy! That saves a lot of large video files flying around the world.
Exactly. And it gets even better. You can even send a small add-on package to update an existing DCP. For example, if a cinema already has the English version of a film, but you later want to add Dutch subtitles, you can send a new mini-package containing just the subtitle file and a new CPL. That new CPL will reference the original video and audio files, combining them with the new subtitles.
Wow. But I assume you can’t just play this on your TV at home.
Unfortunately, no. DCPs are designed to be played on certified DCP servers and projectors - the kind found in cinemas. These systems are built to handle the DCP’s specific file structure and performance requirements, ensuring smooth and stable playback.
So to watch a DCP, I have to go to a cinema?
The purist’s answer is: yes, films should always be seen in the cinema!
There is software that can play DCPs on a computer, but in professional settings, playback almost always happens on certified DCP hardware. That’s largely due to another factor: encryption.
Encryption? So DCPs are protected?
Once again: yes and no. Both encrypted and unencrypted DCPs exist.
Unencrypted DCPs can be loaded and played directly. Encrypted DCPs, however, have their video and/or audio files locked, and require a KDM file to decrypt them.
Another acronym! What’s a KDM?
Tech folks do love their abbreviations. KDM stands for Key Delivery Message. It’s a small but crucial file, usually sent via email, that allows an encrypted DCP to be played. The KDM defines when (date and time) and where (on which specific server) a particular CPL may be played.
If you have multiple screens (and therefore multiple servers), you’ll need multiple KDMs. If your DCP contains multiple CPLs, you’ll also need multiple KDMs - one per version. Without the correct KDM, your DCP simply won’t play.
The combination of encrypted DCPs and KDMs gives rights holders full control over where and when their films are screened.
And that’s why DCPs usually have to be played from a server?
Exactly. Cinema DCP equipment is designed so that the video and audio streams between the server and projector can’t be intercepted or copied, preventing piracy. Software playback on a regular computer is a very different story, which is why KDMs are rarely issued for that.
DCPs, KDMs… all very clever, but also quite technical.
True. But keep in mind: DCP is a global standard. That means if you stick to the specifications, your film can be played in any cinema anywhere in the world.
And considering humanity hasn’t even managed to agree on which side of the road to drive on,or how to measure weight (seriously, how many grams are in a stone?), that’s a pretty remarkable achievement.
Okay, that’s actually pretty cool.
We thought so too.
