What is inside the folder
Open a DCP drive and you'll find a handful of files that only make sense together. Picture and sound each sit in their own MXF files (reels, if the film was split). An asset map and a packing list tell the server which files belong to the package and hold hashes to check they arrived intact. The CPL, or composition playlist, is the file the projectionist actually selects: it strings the reels in order and points to the right sound and subtitle tracks.
The picture is JPEG 2000 in the XYZ color space, at 2K (2048 x 1080 container) or 4K (4096 x 2160). A flat 1.85 film sits at 1998 x 1080 in 2K and a scope 2.39 film at 2048 x 858. Audio is uncompressed 24-bit PCM at 48 or 96 kHz. You can't hand a cinema a Rec. 709 file from the edit and expect it to look right, which is why the DCP is made from the graded master after color grading and the final mix.
Reading a DCP name
Cinemas identify packages by the Digital Cinema Naming Convention kept by ISDCF. A festival print of a fictional feature might be called:
LONGDRIVE_FTR-1_F_EN-XX_US-NR_51_2K_ACME_20260914_SPX_SMPTE_OV
Read left to right: title, content type and version (feature, version 1), aspect (F for flat), audio language and subtitle language (English, no subtitles), territory and rating (US, not rated), 5.1 audio, 2K resolution, studio, date, the facility that made it, the SMPTE packaging standard, and OV for original version. A VF, or version file, is a smaller package that references an OV and adds something, such as French subtitles, without duplicating the picture.
Mistakes that cost screenings
The most common problem is an encrypted DCP arriving without a working KDM, or with a KDM whose window starts after the screening begins. Time zones cause more of these than anything else. Ask for an unencrypted DCP for festival screeners unless a distributor requires encryption.
Other problems show up in the QC report: audio channel mapping swapped between left surround and right surround, subtitle timing drifting at reel changes, or the wrong aspect flag so the cinema masks the frame. A software validation catches file errors, but a test screening in a real auditorium is where you hear a swapped surround or see bad masking, so book one before the drive ships.
Where the DCP sits in delivery
The DCP is one line in the deliverables schedule, alongside the textless master, M&E tracks, and paperwork. It comes after picture lock and the conform, and a post-production supervisor usually budgets the encode, a test screening, and drive shipping as separate lines. For festival submissions, match the DCP spec to the festival's published requirements as part of your festival strategy.