Autor: Redaktion


Creating one master format for TV and film content

The IMF  (Interoperable Master Format) standard enables the interchange of multiple versions of finished media files similar to the Digital Cinema Package (DCP ) of the DCI .

The specification was published in 2013 by SMPTE. Unlike a DCP, which is designed for film distribution to cinemas, IMF is not intended for delivery to the final customer or consumer, but is designed as a pure business-to-business solution.

IMF is a mastering format that provides all that’s necessary for the production of delivery formats in a standardised way. An IMF Master can also hold multiple, customised formats for delivery to different customers. A programme that delivers to multiple global broadcasters, like the BBC’s Planet Earth II, will deliver multiple different versions, which allow for different narrators, closed captions, durations, airline versions and the insertion of different ad-breaks. IMF helps to manage this process.

IMF is modular. An IMF data packet that is exchanged with another partner, which contains a subset of the total IMF media only required for that partner is called an IMP (Interoperable Master Package).

The IMF structure consists of a number of components. These components are divided into a "Composition" and other metadata.

Within the "Composition" are all audio, video, title and subtitle assets and other assets which make up the finished programme, including multiple different audio tracks and narrations.  These assets are references by a Composition Playlist (CPL), which is a little like an EDL and detects where video, audio and other files need to be referenced for the creation of the programme. In addition to the composition and the CPL is the Output Profile List (OPL). This asset map and packing list, serves as a kind of inventory. The OPL includes transcoding instructions for specific, predefined output options from the assets included in the IMP. The OPL will generate the multiple different versions of your programme. Several different outputs can be defined in the OPL, e.g  different voiceovers, or edited versions.

A big advantage of IMF is in more efficient versioning of programmes. It is not necessary to store full AV media essences again and again in each IMP. So if titles need to change, a  resupplied, amended titles file that wasn’t mastered at the same time as the main packet, can also be created and stored for mastering. They only need to reference the IMP and the differences from the original version stores.

Within IMF the AV media essences are defined by the application. This includes codec, frame rate and resolution. SMPTE have defined two application plugins "2" and "2 Extended" for use in broadcast applications. "2" supports SD and HD resolutions with JPEG2000 encoding, "#2 Extended" allows resolutions up to UHD in JPEG2000 coding at 10bit. Other application modules specified are MXF packed uncompressed DPX sequences MPEG4 SStP coding (corresponds to HDCAM SR ), or JPEG2000 coding to 8K.

The aim of the IMF standard, is to keep an output format for all possible deliveries, thereby reducing the storage requirements, simplifying transcoding processes and unifying them.

NABA and the DPP are working on a new broadcast version of IMF currently.

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