DCP stands for Digital Cinema Package and it is the global industry standard format for exhibiting films in cinemas. It was developed in the late 1990s by the cinema industry as the digital replacement for 35mm film, which had sadly become less reliable than digital home entertainment formats.
The main priority with DCP was to create a format that was rock solid for playback. A DCP folder includes media files as well as small computer files that describe the media in great detail - if the media files do not match this description perfectly then it will be rejected. This is a failsafe to prevent any imperfections in the film print and means that, as opposed to disc-based formats, DCP does not deteriorate and once successfully ingested into a cinema server it will play back without failure as many times as required.
Unfortunately the format was never designed to be transferred online (today’s internet speeds were practically unimaginable in the 1990s) but rather loaded onto CRU drives and shipped physically. Common file transfer systems (eg Google Drive, WeTransfer, Dropbox, etc) are not lossless, and tiny bits of data are lost during the transfer process. These may be invisible imperfections to the human eye but they often result in corrupt DCPs as the media files are no longer an exact match with their source. DCPs can also be corrupted simply in the process of zipping & unzipping them.
It is also very difficult to test DCPs outside of a cinema. This means that troubleshooting problems is extremely challenging and can take a very long time as we have to wait until the cinemas are not in use in order to test the hundreds of films that will play at the festival.
Encounters has been screening from DCP (as well as the occasional 35mm print) for well over 10 years and we have developed a deep understanding of our print traffic processes in this time.
To give some idea of how hard it is to troubleshoot a DCP, here is a very real scenario:
A filmmaker receives a DCP from their post production lab on a USB stick. They have no way to test it themselves outside of hiring a cinema but are assured that it works, and when they send the USB stick to festivals it plays fine. In order to transfer it to festivals online here are some common steps that they will take:
Copy the DCP folder onto a laptop (this transfer process can introduce a corruption)
Zip the folder to make it easier to upload (this zipping process can introduce a corruption)
Upload the zipped folder to cloud storage eg Dropbox (this upload process is not lossless and can introduce a corruption)
The festival then downloads the zipped folder from their Dropbox, potentially introducing a corruption in the download process. They also have to unzip it and copy it onto a drive to be taken to the cinema (both steps can of course again introduce corruption) before it is eventually ingested into the server. At this point the server rejects it as corrupted.
It is very very difficult to troubleshoot where exactly the imperfection has been introduced, meaning that unless we go back to shipping the USB stick we cannot be sure that repeating the process from any point in the chain won’t result in the same failure. It may be a number of days or weeks before we can test this particular film in the cinema again (due to the volume of films that must be tested before the festival) and repeated problems can put a film’s participation at risk.
Specialist services like SimpleDCP employ lossless transfer protocols as well as cloud-based DCP software analysis to ensure integrity of the traffic process. If a DCP has become corrupted it will be discovered during the upload/QC process and can be corrected quickly, ensuring that your film can participate in the festival.
