Efficient QC For IMF Workflows

Manik Gupta Abhinav Lokhande Ashish Basu

1. Introduction

In a short span of 10 years, the Interoperable Master Format (IMF) has established itself as the industry's de facto standard for content creation and distribution workflows. It provides numerous advantages in terms of interoperability, versioning, storage, distribution, and workflow automation. These advantages also make IMF the most suitable contender to be used in cloud-based workflows.

As the popularity of the IMF standard continues to grow, it has become crucial for content creators to ensure full compliance with IMF specifications for any package. This has meant that employing automated file-based QC solutions that offer comprehensive and efficient quality control for both original and versioned IMF packages is now essential.

2. Why is QC for IMF important?

IMF is based on the SMPTE ST-2067 series of specifications, which is defined with a highly modular approach. The specification defines the core framework and the various implementations — called applications — derived from this core framework.

This independent and modular architecture of IMF also increases the risk of violating standard constraints. This makes it even more important for an automation tool to ensure compliance with codec specifications defined in the respective applications, while simultaneously ensuring integrity with the core framework.?

In the next few sections, we’ll explore how comprehensive QC should be performed for both original and version IMF packages.

3. QC of Original IMF Packages

Content creators must perform in-depth analysis of an IMF package using an automated content verification system — one that is continuously aligned with the latest developments and one that adopts the trends of an evolving IMF specification. It should perform integrity checks on the IMF structure XMLs, ensuring that the core framework isn’t violated, and deep analysis of the underlying video and essences, including:

Complex Composition Structure

An IMF package can be complete, containing all the referenced constituents, or it might depend on original packages for one or more video and audio main essences.

The QC solution should also ensure that the IMP contains all the relevant files. Moreover, it should ensure that file size and checksum (the value that represents the number of bits in a transmission message) for each file is correct and as per the value encoded in a PKL file.

Metadata Consistency

There is an overwhelming amount of IMF metadata contained in various XML files (CPL), including the MXF container of each video, audio, and data essence, and the actual essence itself. The first challenge is to read and assimilate the metadata available at various levels of the distributed content structure, and the second is to ensure that it is consistent at all levels.

In-Depth Verification of Video Audio Essence

The in-depth verification of underlying video, audio, and subtitles is equally important. Each essence needs to be checked for compliance with MXF and corresponding audio/video/subtitle specifications. Each essence should be fully decodable without any conformance error.

Once the above checks are executed, a comprehensive quality check of audio and video should be performed to ensure high-quality delivery. Video essences should be assessed for valid color gamut, RGB levels, freeze frames, black frames, color bars, PSE, and more. Audio also needs to be checked for loudness, silence, test-tones, and audio clicks.

Processing Modes

The size of IMF packages can easily vary from a few hundred gigabytes to a few terabytes, which means processing these media files can be extremely time consuming.

High-speed content analysis can be achieved to some extent by using modern and fast GPU based decoders wherever possible. Another approach is to use different analysis strategies, such as in-depth analysis or high-level analysis of the content. In the case of high-level analysis, only the header metadata will be parsed and validated, skipping the essence decoding. On the other hand, an in-depth analysis will carry out the complete decoding and metadata validation. This gives users an opportunity to choose a QC strategy that fits their schedules and delivery commitments.

4. QC of Versioned IMF PACKAGES

QC of versioned packages should be limited to QC of newly introduced tracks or segments in that package only, without verifying the original package. This will ensure efficiency in QC workflows. Moreover, it is important that a QC solution should be able to address the below complexities related to versioned packages:

·??It should be able to locate all the required essences, which are spread over multiple content locations and packages

·??It should assign the correct timestamps for verification when multiple essences are being merged to create a composition as per CPL??????????????????????????????

Conclusion

For content creators and postproduction houses, it is difficult to keep track of a complex and evolving standard like IMF, and to continuously upgrade their setups or workflows to suit the dynamic environment. The nexus of XML files gives the necessary functionality to hold the content timeline, update content location as needed, store content hash values to ascertain content integrity, and store only the changes to optimize storage and network bandwidth. Hence to address the complexities of an IMF workflow, industry requires a continually evolving automated QC tool that is always up to date. The solution should perform in-depth analysis of IMF structure and video, audio, and data, with minimal human intervention.

Interra Systems offers leading ML- and AI-driven file-based QC solutions such as BATON, which offer comprehensive quality checks and verification efficiency in a flexible environment.? BATON meets all the above stated requirements, from analyzing various flavors of IMF to deep analysis of audio video essence. As the most widely deployed QC solution in IMF workflows, BATON has the most extensive audio and video quality checks available to ensure delivery of pristine content for all downstream applications.