What is the DCP format?

What is a DCP or a Digital Cinema Package?

It is the video file format used in cinemas.

The first DCPs were made in the Interop format which only supported 24/48 FPS and unencrypted subtitles.

Today many big Hollywood films are delivered in the SMPTE format in Norway and other countries. SMPTE DCPs have support for Atmos sound, additional frame rates like 25, and encrypted subtitles.


Support for exporting DCPs

You can export and view Interop/SMPTE DCPs in DaVinci Resolve Studio that costs €249. I wrote a post about it here.

CPU JPEG2000 DCP encoding can be slow. It can be as slow as 5 FPS on 4K and grainy sources even on moderately fast computers.

You can make and view more advanced DCPs in Easydcp plus. I wrote a post it here.

It supports faster NVIDIA CUDA GPU JPEG2000 DCP encoding, which can reach real-time 24 FPS and higher FPS even on 4K and grainy sources.

A free alternative to make and test DCPs is
DCP-o-matic/DCP-o-matic player.
I have used it on JPEG pictures and PSA/ad MP4 video files.
I wrote a post about it here.

Some general guidelines for delivering in the DCP format

  1. Make the DCP in 4K or 2K. 4K DCPs will usually be larger than 2K DCPs because 4K will max out the 250 mbit bitrate of DCPs. The 2K portion of a 4K DCP will use a maximum of 200 Mbits/sec per color component.
  2. The normal frame rate for an Interop DCP is 24 FPS. If the film is 25 FPS, it is best to avoid converting to 24 FPS. Most cinemas can play 25 FPS SMPTE DCPs. To be safer you can make 25 2K DCP instead of 4K DCP even if most systems support them.
  3. If you need to deliver a 25 FPS film as a 24 FPS Interop DCP, avoid frame dropping and phase problems with the sound. I wrote a post about it here.
  4. Make the DCP in DCI Flat 1.85:1 or DCI Scope 2.39:1. Do not use DCI Full Container, it is not in use.
  5. Use a DCI resolution:
    4K Scope 2.39:1 4096 1716
    4K Flat 1.85:1 3996 2160
    2K Scope 2.39:1 2048 858
    2K Flat 1.85:1 1998 1080
  6. Make the DCP from a uncompressed or high bit rate source that supports the DCI resolutions:
    -16 bit TIFF image sequence
    -Prores 422 HQ/4444
    -DnXHR HQ 10 bit
  7. DCPs can be made from films in rec.709 or P3 color space. Not Rec.2020 and similar color spaces, a film in Rec.2020 have to be converted to Rec.709 or P3 before making the DCP.
  8. Deliver the film with a 5.1 soundtrack. 2 channel stereo is not commonly used in cinemas. I wrote a post about converting stereo to 5.1 here.
  9. If you want to deliver a DCP with a 7.1 soundtrack, deliver a 5.1 DCP with a supplemental pack/Version File that adds a 7.1 soundtrack. I wrote a post about it here.
  10. When the aspect ratio is less than 2.39:1 (Scope) like 2.2:1, the Hollywood DCPs have been delivered letterboxed in Flat with subtitles above the letterboxing. I wrote a post about it here.
  11. Soft subtitles often use Arial or a similar font, around 38-42 in size, and around 8 percent from the edge of the picture. I wrote a post about subtitles here
  12. You can often deliver the DCP as a download link, which I wrote about here. Or on a MBR EXT2/NTFS formatted hard drive, which I wrote about here.

SMPTE DCP Bv2.1

SMPTE RDD-52 – “D-Cinema Packaging — SMPTE DCP Bv2.1 Application Profile” is a free document that describes the SMPTE DCP format endorsed by some of the largest DCP labs in 2020.

They restrain SMPTE Bv2.1 DCPs to these formats:
2K Scope 2048×858 24/25/48 FPS 2D/3D
2K Flat 1998×1080 24/25/48 FPS 2D/3D

4K Scope 4096×1716 24 FPS 2D
4K Flat 3996×2160 24 FPS 2D

Note:
The document says that the closest container to the aspect ratio of the movie should be used, but the industry practice is to use Flat for aspect ratios that are closer to 2.39. One example is Flat 2.2:1, it was used on the non-IMAX Tenet DCP.

When a 2.2:1 film is mastered in Flat, the side masking setting for Flat fits. If a film was delivered in 2.2:1 Scope, the common width cinemas that have a 1.85:1 screen would have to make a custom preset to avoid a pillarboxed and letterboxed picture. And common width cinemas with 2.39 screens would have to make custom digital side masking.

DCP Format specifications

-Max P3 Color space
-2K/4K resolution
-2.6 gamma
-12 bit
-250 Mbit JPEG2000
-Uncompressed sound

The DCP format was chosen after a lot of tests on what digital format could match 35 mm prints in quality: The tests that were done are described in the book:
Coloring and Mastering for Digital Cinema (google search)

-P3 color space was already in use in post-production around 2000, color grading was done on DLP 3 chip Xenon lamp projectors. The P3 color space has more saturated colors than Rec.709, especially red.

250 Mbit intra-frame JPEG2000 encoding was chosen because:
-It supports both 2K and 4K.
-Each frame is encoded separately so film grain is retained.
-The high bitrate helps detail-rich scenes like forest and ocean scenes to look good.

-12-bit encoding was chosen because it lets you retain more shadow detail and avoid banding in grey areas and skies.

-2.6 gamma is similar to the LOG encoding used in film scans and digital cinema cameras. The steep 2.6 gamma slope together with 12-bit encoding lets you encode more shadow detail.

-24 bit 48 kHz uncompressed 5.1 sound was used in post-production. Later 7.1 audio and Dolby Atmos were added.

Version File/ Supplemental package DCP

The original version (OV) of the DCP is often the film with original language and no subtitles. This OV DCP is sometimes sent ahead of the DCP with dubbed language and subtitles to the cinemas. This DCP is called a Version File (VF) DCP or a supplemental package DCP. The VF DCP reference the MXF files in the OV DCP. The VF DCP typically adds dubbed language tracks, subtitle tracks, and 7.1 sound. I wrote a post about it here.

Encrypted and unencrypted DCPs

Feature films are often encrypted and you need a decryption key (KDM) to play the movie. I wrote a post about it here.

Short films, advertisements, and trailers are usually unencrypted.

The content of a Digital Cinema Package (DCP)

The XML files in a DCP consist of:
-the video MXF files,
-the audio MXF files,
-the subtitle MXF (SMPTE) files
-XML + TTF font (Interop),
and the metadata files: Volindex, Assetmap, The Packing List (PKL), and the Composition Playlist (CPL).

The CPL XML file is a playlist that lists the MXF files in each reel, the order of the reels, and the offset on the video and audio MXF files.

The PKL XML file lists all the MXF files in the DCP and has a hash checksum of the files for verification. If the files do not pass the hash checksum test because they have been corrupted in a transfer they will not ingest on the server.

You can run a Hash checksum test on DCPs in the trial version of Easydcp plus

Drag the DCP to Easydcp player

Choose Asset – Hash Checker
In Hash Checker
Choose start

DCI Specifications

A DCI DCP means that the DCP is made with the current DCI specification. The DCI specification was agreed upon by the big Hollywood studios in 2005 and has been updated regularly.

The current DCI specification tells us to follow these SMPTE standards when making a DCP:

ST 428-1:2019 – SMPTE Standard – D-Cinema Distribution Master — Image Characteristics

RP 431-2:2011 – SMPTE Recommended Practice – D-Cinema Quality — Reference Projector and Environment

RP 431-2:2011 references:
ST 431-1:2006 – SMPTE Standard – D-Cinema Quality — Screen Luminance Level, Chromaticity and Uniformity

The archived DCI specification 1.2 has parts of earlier versions of these standards in the document. The standards have changed since then as errors have been corrected and equipment has improved.

Some current DCI DCP/cinema specifications:

  1. DCI DCPs uses these ST 428-1:2019 example aspect ratios:
    Scope 2.39:1 4096 1716
    Flat 1.85:1 3996 2160
    Scope 2.39:1 2048 858
    Flat 1.85:1 1998 1080
  2. ST 431-1:2006 tells us to use 14 fL/48 cd/m2 screen brightness with a DCI white test image, (16 fL with a projector white test image.) If the screen brightness is much lower or higher when screening the DCP, the colors, contrast and details will look different.
  3. RP 431-2:2011 calibration white was changed to virtual white (50.34832, 0.3190, 0.3338). The old RP- 431-2:2007 DCI White (48.00, 0.314, 0.351.) is also still in use.
  4. The minimum pixel count in RP 431-2:2011 is at least 2048×1080, so a DCI cinema uses a zoom lens to switch between Flat and Scope.
  5. RP 431-2:2011 says to use side masking for both Flat and Scope.

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