Outlook 2016: File Formats - There's a light at the end of the post tunnel
Dr. Siegfried Foessel
Issue: December 1, 2015

Outlook 2016: File Formats - There's a light at the end of the post tunnel

Movie production is facing hundreds of different file formats. Each camera delivers content in its own format, and each display device requires an optimized distribution format for the best viewing experience. New media devices and systems with extended resolutions, color space and dynamic range appear daily. This leads to complex workflows and extensive work in post production implementing device-specific format adaptations. 

Wouldn’t it be nice to have only one or just a handful of formats? An all-purpose post production or mastering format would minimize requirements and costs for post production. For this reason, a series of post production formats were developed with the hope of intersecting the paths of the production and playback worlds. A background on each follows.

In the past, only a few specific formats were used. Some were proprietary, others standardized. Each was handled individually to get the best quality at the end. With the diversity of formats today, this is no longer possible. An early approach was to use a standardized format, like the Material Exchange Format (MXF), as an intermediate format. This is an excellent format, but its general version allows too much variation in profiles, codecs and structuring. As a consequence, interoperability could not be achieved. This issue became bigger as the number of formats and post production companies involved in the workflow increased.

As a result, joint efforts started. Some were based on the needs of national broadcasters. This includes the Digital Production Partnership (DPP) specifications in the UK, driven by the BBC and the Technical Production Guidelines for Television in Germany, driven by the IRT. They use MXF as a wrapper format. But these formats are strictly constrained to a limited set of parameters and structure options, with only a few, specific codecs allowed. This facilitates interoperability between different tool manufacturers, allowing successful use in the broadcast world. Organizations like the Advanced Media Workflow Association (AMWA) are expanding participation to additional tool manufacturers and broadcasters to discuss further interoperability aspects.

SMPTE, the Academy of Motion Picture Arts and Sciences (AMPAS), and Hollywood studios followed another approach. Their solution couldn’t focus on a specific distribution channel. Their content is not only intended for cinema or broadcast. It’s also adapted for VOD and OTT services for all types of home and mobile devices. Additionally, future formats like high dynamic range (HDR) or different color spaces (ITU.BT 709, P3, ITU-BT 2020, XYZ) have to be considered.

The starting point for the aforementioned formats was the replacement of film reels by the Digital Cinema Package (DCP). This is also a MXF format with clear constraints and JPEG2000 as a compression codec. With its high bit rate of 250 Mbit/s and its high bit depth of 12-bit per color component, it targeted the quality demands and expectations of the new digital cinema world. Interoperability was pivotal to allow worldwide distribution of the DCP similar to what was accomplished with film. Many interoperability tests were executed, successfully harmonizing the DCP. 

The DCP’s success in cinema resulted in a new project called the Interoperable Master Format (IMF). IMF is a universal, device-agnostic and intermediate format for exchange of media content for all non-theatrical distributions and the output format for post production. The related package is an Interoperable Master Format Package (IMP). The format contains audio, video or metadata like subtitles and defines Output Profile Lists (OPL). The OPL describes the necessary processing steps to create a specific distribution format, such as an HD HEVC TV format or an Internet streaming format for a smartphone. The DCP and IMP are standardized by SMPTE and are targeted ISO standards.

The Academy Color Encoding System (ACES) is a format dedicated to harmonizing color representation during post production. Based on experiences with color LUTs for film, this format is designed to guarantee the best-possible color viewing experiences for decades of movie production. With the use of device-specific color transformations, a color accurate transition between different cameras and display devices is possible. ACES uses half-float representations of color components in an OpenEXR format. Encapsulation within IMF is planned for the future.

With the DCP for cinema, IMF for broadcast, VOD and OTT and ACES for color reproduction, a solid set of formats is available to improve the post production workflows of today and tomorrow. Fraunhofer supports standardization activities and interoperability tests for DCP and IMF. These formats are integrated into our easyDCP Software Suite either as standalone tools or as plug-ins for third-party manufacturers, such as Blackmagic Design or SAM.

Dr. Siegfried Foessel is the Head of the Department Moving Picture Technologies at Fraunhofer IIS (www.iis.fraunhofer.de) in Erlangen, Germany.