The “Intermediate Cinema” IMF format is an exact technical specification – an application – linked to a broader format family standardized by the SMPTE: the IMF (Interoperable Master Format). This format was initially proposed, by the CST working group in 2013, as an appendix to recommendation RT-021 before going through the SMPTE standardization process and it was finally published in 2016 under reference SMPTE ST 2067-40.
Today, its best known utilisation is the extended Application 2, “Studio Master”, which Netflix uses as its delivery format.
The IMF uses the architecture of DCP files and extends their possibilities. Pictures, sound and sub-titles are stored in separate MXF files known as essences.
A CPL (composition play list) provides the indication of the assembly that must be carried out to read the various elements in the final medium. This file is in SML format and can easily be consulted, even without a specialised editor.
The IMF format also includes the notion of packaging, i.e. a delivery unit comprising a certain number of files, whether these are CPLs or essences.
One of the main advantages of this format is to be able to provide incremental deliveries. For example, a package can be delivered containing the master of a film’s original version with sound elements from the original version and the pictures. A second package can then be delivered with a CPL referencing assets in the first package, without delivering them again. This means the French sound can be sent alone, along with pictures including titles, without sending the whole film.
The IMF introduces a new file type that does not exist in DCPs: the OPL. This allows for guiding the conversion of the master sent, towards a file linked to a specific requirement. For example, it can pilot the transcoding to a master for television broadcasting with black bands or pan & scan, to a broadcasting colour range and the required audio channels.
This way of working ensures coherence and saves storage space and bandwidth.
All the IMF specifications were kept by the SMPTE. A set of standards defines the core constraints, the format’s common base. Following this comes a standard for each application to specify the constraints depending on the field of application and its various professional uses.
The most commonly used application today is the extended IMF application 2, which is required by Netflix. It should be noted that the firm has exhaustive specifications that specialise even further the constraints for its particular requirements.
Application 4 – Intermediate Cinema
The purpose of App#4 Intermediate Cinema is to constitute a high quality master for cinematographic films. All the technical specifications were chosen to ensure quality and avoid ambiguity.
4K or 8K pictures can be stored in MXF containers using JPEG 2000 lossless compression and pixel storage on non-signed primary full 16-bits integer. The colorimetric range used is non pre-compensated XYZ.
List of solutions supporting IMF application #4 – Intermediate Cinema
This format is now implemented by the main constructors of encoding solutions.
- Rhode & Schwarz Clipster (V6)
- Marquise – Mist
- Colorfront – Transkoder
- QC IRT Analyzer