Audiovisual Defect and Quality Description

In audiovisual production, archiving and restoration the description of the technical condition of material and the recognized defects is an important piece of metadata. There are proprietary formats of some restoration systems to describe this kind of metadata, but there is no standardized way to describe material quality and defects. In MPEG-7 (partly MDS and partly AMD1 to part 4) already some quality and defect descriptors and description schemes have been defined, with more focus on the audio modality.

The MPEG-7 standard is well-suited to be used as the basis for audiovisual defect and quality descriptions. Thus a number of description schemes and descriptors adding the capabilities for the describing audiovisual quality and defects have been defined.

Defect and Quality Description Schemes and Descriptors

The following description capabilities have been defined:

• A general description scheme for visual defects and quality measures, complementary to the existing AudioSignalQuality description scheme. A defect is identified by a reference to a controlled vocabulary, a classification scheme for defects and quality measures.
• An extensible set of specific descriptors for visual quality measure and defect description, e.g. Dropout/Partial Frame Damage, Line Scratches, Full Frame/Channel Damage, Dust/Dirt Level, etc. For each quality measure or defect a number of properties, such as defect description, the temporal/spatial scope, strength, etc. are given.
• Extension of the AudioSignalQuality description scheme by specific audio quality and defects descriptors, e.g. Pitch Shift or Wow&Flutter.

Impairment Classification Scheme

The defect and quality classification schemes which are currently defined in MPEG-7 only specify a few visual and audio defects. It is crucial to define comprehensive defect classification schemes, as they will serve as the basis for future defect and quality descriptions using MPEG-7.

The PrestoSpace Impairment Classification Scheme, which is based on the BRAVA broadcast archive programme impairments dictionary, contains the following information:

• A classification of the defects.
• A hierarchical structure of the defects, e.g. a dropout defect and several specialized kinds of dropouts.
• Multilingual defect names and textual descriptions.

Available Resources

A report containing an analysis on using MPEG-7 for defect and quality description and the definition of the proposed description schemes, descriptors and classification schemes, are available. The report, the definition of the extensions and the classification schemes are available in the download area.

This work has been funded partially under the 6th Framework Programme of the European Union within the IST project PrestoSpace, under the FIT-IT programme of the Austrian Federal Ministry for Transport, Innovation and Technology within the project vdQA and under the 7th Framework Programme of the European Union within the ICT project PrestoPRIME