MPEG-7 Audio Overview Beinan Li MUMT 611 Week 2 2005. 1. 20.
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Transcript of MPEG-7 Audio Overview Beinan Li MUMT 611 Week 2 2005. 1. 20.
MPEG-7 Audio Overview
Beinan Li
MUMT 611 Week 2
2005. 1. 20
Content
MPEG-7 overviewWhat is…Why?Objectives and scopeMain elements and organization.
MPEG-7 AudioLow-level featuresHigh-level tools
What is MPEG-7 "Multimedia Content Description Interface“ ISO/IEC standard by MPEG (Moving Picture Experts Group)
Providing meta-data for multimedia MPEG-1, -2, -4: make content available;
MPEG-7: makes content accessible, retrievable, filterable, manageable (via device / computer). Multi-degrees of interpretation of information’s meaning Support as broad a range of applications as possible. A compatible (with existing tech) and extensible standard.
Why MPEG-7 “The value of information often depends on how
easy it can be found, retrieved, accessed, filtered and managed. ”
Past: poverty of the digital multimedia sources -> Simplicity of the access mechanisms
Now: growing amount of audiovisual information-> Identifying and managing them efficiently is becoming more difficult.e.g. “record only news about sport.”
Why MPEG-7 For future multimedia services, content representation and
description may have to be addressed jointly. Many services dealing with content representation will
have to deal first with content description “a non-described content may be useless”
Need for access only to the content description: New original services (e.g. optimizing personal time) Adaptation to networks and terminal capabilities
Application’s domains (incomplete)
Broadcast media selection (e.g., radio channel, TV channel). Digital libraries (e.g., film, video, audio and radio archives). E-Commerce (e.g., personalized advertising). Education (e.g., repositories of multimedia courses, multimedia
search for support material). Home Entertainment (e.g., management of personal multimedia
collections, including manipulation of content, e.g. karaoke). Journalism (e.g. searching speeches of a certain politician using his
name, his voice or his face). Multimedia directory services (e.g. yellow pages, G.I.S). Surveillance and remote sensing.
MPEG-7 Objectives
Standardize content-based description for various types of audiovisual information
Independent from media support (encoding and storage)
Different granularity Low-level features: shape, size, key, tempo changes, High-level semantic info: “scene with a barking brown dog on
the left and with the sound of passing cars in the background.”
Meaningful in the context of the application Same material -> different types of features and combinations
e.g. timbre v.s. loudness
MPEG-7 Objectives Information about the content
The form: e.g. the coding format used
Conditions for accessing the material:e.g. Intellectual property rights / price
Classification: e.g. parental rating
Links to other relevant materials The context: “e.g. Olympic Games 1996, final of 200 meter hurdles, men)”
Information present in the content: Combination of low-level and high-level descriptors
Scope of the Standardprocessing chain:
An example of architecture
Pull: (Client Queries -> Descriptions repository -> Matched Ds) Push: (Filter descriptions -> Programmed actions)
Workplan
Where are the descriptions from?
Preservation of existing descriptive data (e.g. scripts) through the production/delivery
Generated automatically by capture devices (e.g. time or GPS location in a camera)
Extracted automatically & semi-automatically (i.e. with some human assistance)
Manually produced (e.g. for legacy material such as existing film archives)
Main Elements of MPEG-7
Description Tools: ( textual / binary ) Descriptors (D): define the syntax and the semantics of each
feature (metadata element) Description Schemes (DS): relationships between components
Description Definition Language (DDL): Define the syntax of the MPEG-7 Description Tools Creation , extension and modification of DSs
System tools: Storage and transmission, synchronization of descriptions with c
ontent, multiplexing of descriptions, etc.
Main Elements of MPEG-7 Relationship among elements introduced above.
Description Tools Creation and production processes: (director, title) Usage: (broadcast schedule) Storage features. Structural information: (spatial-temporal components)
Segmentations Low level features: (sound timbres, melody description) Conceptual information: (objects and events, interactions) Navigation and access: (summaries, variations) Collections of objects. User-content interactions: (user preferences, usage history)
Organization of Description Tools
Descriptions (further) MPEG-7 approaches the description of content from
several viewpoints. A set of methods and tools for the different viewpoints of
the description (not a monolithic system) Interrelated and can be combined in many ways. Associated with the content itself: (searching, filtering) Location: (document V.S. stream)
physically located with the material somewhere else on the globe (maybe not)
Interoperability with other metadata standards: (XML)
Use of Description Tools The description tools are presented on the basis of the fun
ctionality they provide. In practice, they are combined into meaningful sets of des
cription units. Furthermore, each application will have to select a sub-set
of descriptors and DSs. Library of tools! DDL can be used to handle specific needs of the application. (like scripting in many current applications)
Major Functionalities MPEG-7 Systems MPEG-7 Description Definition Language MPEG-7 Visual MPEG-7 Audio MPEG-7 Multimedia Description Schemes (D.T.)
Reference Software: the eXperimentation Model (test)
MPEG-7 Conformance (syntax checking)
MPEG-7 Extraction and use of descriptions (technical report)
MPEG-7 Audio
Audio provides structures—building upon some basic structures from the MDS—for describing audio content.
Low-level Descriptors:audio features that cut across many applications
High-level Description Tools:more specific to a set of applications.
Low-level Features “MPEG-7 Audio Framework”: Two low-level descriptor types: (for sample and segment)
Scalar : (e.g. power or fundamental frequency) Vector : (e.g. spectra)
Hierarchical, consistent interface Any descriptor inheriting from these types can be instantiated,
describing a segment with a single summary value or a series of sampled values, as the application requires.
Scalable Series: (hierarchical re-sampling) Progressively down-sample the data contained in a series
(Application-oriented)
Low-level Features (types)
Basic Basic Spectral Signal Parameters Timbral Temporal Timbral Spectral Spectral Basis MPEG-7 Silence Descriptor
Low-level Features (graph)
Low-level Features (details)
Basic: (temporally sampled scalar values for general use)
AudioWaveform Descriptorwaveform envelope: (for display purposes).
AudioPower Descriptortemporally-smoothed instantaneous power:
(quick summary of a signal)
Applicable to all kinds of signals
Low-level Features (details)
Basic Spectral: (single time-frequency analysis of signal) AudioSpectrumEnvelope: (Base class)
the short-term power spectrum:
(display, synthesize, general-purpose search)
AudioSpectrumCentroid: dominated by high or low frequencies ?
AudioSpectrumSpread: the power spectrum centered near the spectral centroid, or spread out over
the spectrum? pure-tone and noise-like sounds
AudioSpectrumFlatness: (the presence of tonal components)
Low-level Features (details)
Signal Parameters: (periodic or quasi-periodic signals)
AudioFundamentalFrequency:“confidence measure”, replacing “pitch-tracking”
AudioHarmonicity:distinction between sounds with a
harmonic / inharmonic / non-harmonic spectrum
Low-level Features (details)
Timbral Temporal: (temporal characteristics of segments of sounds, musical timbre)
LogAttackTimeTemporalCentroid
where in time the energy of a signal is focused.Useful when attack times are identical
Low-level Features (details)
Timbral Spectral: (spectral features in a linear-frequency space) SpectralCentroid:
power-weighted average of the frequency
of the bins in the linear power spectrum.distinguishing musical instrument timbres
4 Ds for harmonic regularly-spaced components of signals:HarmonicSpectralCentroidHarmonicSpectralDeviationHarmonicSpectralSpreadHarmonicSpectralVariation
Low-level Features (details) Spectral Basis: (low-dimensional projections of a spectral space to aid co
mpactness and recognition)
AudioSpectrumBasis: a series of (time-varying / statistically independent) basis functions deriv
ed from the singular value decomposition of a normalized power spectrum.
AudioSpectrumProjection: low-d features of a spectrum after projection upon a reduced rank basis.
independent subspaces of a spectra correlate strongly with different sound sources.
Provide more salience using less space. With Sound Classification and Indexing Description Tools.
Low-level Features (details)
Silence segment: (no significant sound) aid further segmentation of the audio stream, or as a hint not to
process a segment
High-level audio Description Tools (Ds and DSs)
Exchange some generality for descriptive richness: a smaller set of audio features (as compared to visual features)
that may canonically represent a sound without domain-specific knowledge.
Audio Signature (DS)
Musical Instrument Timbre Melody General Sound Recognition and Indexing Spoken Content
High-level audio Description Tools (details)
Audio Signature Description SchemeSpectralFlatness Dsa unique content identifier for the purpose of robust aut
omatic identificatione.g. audio fingerprinting
High-level audio Description Tools (details)
Musical Instrument Timbre Description ToolsHarmonicInstrumentTimbre Ds:
LogAttackTime Descriptor
PercussiveIinstrumentTimbre Ds:SpectralCentroid Descriptor
High-level audio Description Tools (details)
Melody Description Tools: efficient, robust, and expressive melodic similarity mat
ching.MelodyContour Description Scheme:
terse, efficient melody contour / rhythmMelodySequence Description Scheme:
verbose, complete, expressive melody / rhythm.Interval encoding
High-level audio Description Tools (details)
General Sound Recognition and Indexing Description Tools: SoundModel Description SchemeSoundClassificationModel Description Scheme
a set of SoundModel DS -> multi-way classifierSoundModelStatePath Descriptor
indices to states generated by a SoundModel of a segment immediately applied to sound effectsautomatically index and segment sound tracks.Low -> mid -> high level analyses
High-level audio Description Tools (details)
Spoken Content Description Tools: detailed description of words spoken within an audio
stream. indexing into and retrieval of an audio stream indexing of multimedia objects annotated with speech.
Recall of audio/video data by memorable spoken events. a character or person spoke a particular word
Spoken Document Retrieval separate spoken documents
Annotated Media Retrieval photograph retrieved using a spoken annotation
Development Currently under development:
MPEG-7 Audio COR.1 (currently at DCOR1) MPEG-7 Amendment 1 (currently at FPDAM1)
New Audio Description Tools specified (MPEG-7 version 2): Spoken Content: Audio Signal Quality: Audio Tempo:
Currently Proposed tools: Low Level Descriptor for Audio Intensity Low Level Descriptor for Audio Spectrum Envelope Evolution Generic mechanism for data representation based on ‘modulation
decomposition’ MPEG-7 Audio-specific binary representation of descriptors
MPEG-7 version 1 Schedule Call for Proposals October 1998 Evaluation February 1999 First version of Working Draft (WD) December 1999 Committee Draft (CD) October 2000 Final Committee Draft (FCD) February 2001 Final Draft International Standard (FDIS) July 2001 International Standard (IS) September
2001
MPEG-7 work plan:
See :
Annex A of MPEG-7 Overview (version 9) http://www.chiariglione.org/mpeg/standards/mpeg-7/mpeg-7.htm
Annotated Link Page / References
http://www.music.mcgill.ca/~damonli/611/611_w2.htm
All pictures taken from: P. Salembier and O. Avaro, “MPEG-7: Multimedia Content Description inter
face”,
http://gps-tsc.upc.es/imatge/_Philippe/demo/MPEG21_MPEG7.pdf