Deliverables: IMF packages, masters and versions

A streaming title is delivered as a set of files and documents, not as a single movie file. The picture alone may include an HDR master, an SDR version, textless backgrounds, alternative versions for different territories and inserts for titles and credits, all of which must line up exactly with dozens of audio tracks and subtitle files. Streaming services handle this complexity with the Interoperable Master Format (IMF), a family of SMPTE standards that packages picture, sound, text and metadata into components that can be reused and recombined. This lesson explains what IMF is, how packages are structured, what other masters services ask for, how frame rates and safe areas affect delivery and how to estimate storage. Cinematographers do not usually build IMF packages, but understanding them explains many requests that come back from finishing and QC.

The deliverables list

Every production receives a deliverables list or schedule from the service or distributor. It lists each item, its format and deadline. A typical picture section might include:

• HDR master: IMF package with JPEG 2000 picture, PQ, Rec. 2020 container, with Dolby Vision metadata.
• SDR version: derived via metadata or delivered as a separate IMF composition or file.
• Textless elements: the picture without burned-in titles, subtitles or graphics, so titles can be replaced for other languages.
• Inserts: localized title cards, credits and on-screen text for other languages.
• Trailers and promotional materials, which may have their own specifications.
• Archival or legacy formats, such as ProRes files for partners.

The sound, timed text, artwork, metadata and legal sections add many more items. Missing or late deliverables delay a title's launch, so post supervisors track them closely.

What IMF is

IMF is defined by the SMPTE ST 2067 family of standards. Instead of baking every version into a separate file, IMF stores the content as track files and uses playlists to describe how to assemble them. Key parts:

• Track files: MXF files that each hold one kind of essence, such as the main picture, one audio language or one subtitle language.
• Composition playlist (CPL): an XML file that lists which parts of which track files make up a version, in order, with timing. One package can hold several CPLs, such as the original version and a localized version.
• Packing list (PKL): an XML file that lists every file in the package with its size and hash, so delivery can be verified.
• Asset map: an XML file that tells systems where each file is located.
• Output profile list (OPL): optional XML instructions for how to make a specific output, such as scaling or converting to a particular format.
• Application: a set of constraints for a particular use. Application 2E (SMPTE ST 2067-21) is widely used for UHD and HDR content with JPEG 2000 picture; other applications cover ProRes picture or ACES image data.

Supplemental packages and versioning

One of IMF's strengths is versioning. If a title needs a French version with French title cards and credits, the finishing team does not render a whole new picture. Instead, it creates a supplemental package containing only the new title-card segments and a new CPL that points to the original picture for most of the runtime and to the new segments where needed. The same approach handles censorship edits for some territories, corrected shots after QC and new audio or subtitle languages.

Picture encoding in IMF

For UHD and HDR deliveries, many services ask for JPEG 2000 picture in IMF, often lossless or visually lossless, at 10 or 12 bits. JPEG 2000 compresses each frame independently, which keeps editing and quality control simple. Some services accept or request ProRes-based IMF or separate ProRes master files for certain uses. Data rates depend on content, resolution and settings: grainy, detailed images need more data than clean, simple ones.

Use the figures in the table only for planning. For exact ProRes data rates, check Apple's ProRes documentation; for JPEG 2000, measure a sample of your own content.

Textless elements and inserts

Textless elements are copies of every shot that carries text, such as titles, locations, captions or graphics, without the text. They let localization teams add translated text without re-grading. Some services want textless versions of whole episodes; others want only the affected shots, delivered with handles (a few extra frames before and after). Inserts are the localized or alternative segments themselves. For the cinematographer, the main point is to make sure the textless backgrounds are graded identically to the texted versions and that frames with on-screen text are noted early in the grade.

Frame rates, conversions and pulldown

Masters are delivered at the project frame rate, but some partners or territories need other rates. Common conversions:

• 23.976 to 29.97 fps: 2:3 pulldown repeats fields in a pattern, so four film frames become five video frames (ten fields). Modern streaming rarely needs this, but some broadcast partners still do.
• 24 or 23.976 to 25 fps: usually done by playing the picture about 4.1 % or 4.3 % faster, which shortens runtime and raises audio pitch unless pitch-corrected.
• Frame-rate conversion by interpolation: used for some difficult conversions, but it can create artefacts.

Safe areas and active picture

Delivery specifications often refer to safe areas, which come from broadcast practice and help protect important picture content and text on different displays.

• Action safe: the area inside which all important action should stay, often about 93 % of width and height (SMPTE ST 2046-1 recommends this).
• Title safe or graphics safe: the area for text and graphics, often about 90 %.
• Active picture: the part of the frame that contains image, excluding letterbox bars. For a 2.39:1 picture in a 3,840 × 2,160 container, active picture is about 3,840 × 1,607.

Many streamers allow text closer to the frame edge than broadcast did, but subtitles, captions and graphics must still avoid being cut off on devices that crop or overscan. Lesson 8 covers subtitle placement.

Delivering the files

IMF packages and other masters are delivered over high-speed file transfer services or, sometimes, on physical drives. Delivery systems check file hashes against the PKL, validate the package against the IMF application rules and run automated QC. Errors at this stage, such as a missing file or a wrong frame rate in the CPL, cause immediate rejection. Finishing facilities use IMF validation tools before sending. For a cinematographer, the relevant points are to know the delivery deadline, to finish grading and approvals in time for packaging and QC, and to be available if QC flags picture issues.