1. MPEG-7 Audio Overview
Beinan Li
MUMT 611 Week 2

2. Content MPEG-7 overview MPEG-7 Audio What is… Why?
Objectives and scope
Main elements and organization.
MPEG-7 Audio
Low-level features
High-level tools

3. 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.

4. 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.”

5. 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

6. 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.

7. 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

8. 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

9. Scope of the Standard
processing chain:

10. An example of architecture
Pull: (Client Queries -> Descriptions repository -> Matched Ds)
Push: (Filter descriptions -> Programmed actions)

11. Workplan

12. 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)

13. 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 content, multiplexing of descriptions, etc.

14. Main Elements of MPEG-7
Relationship among elements introduced above.

15. 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)

16. Organization of Description Tools

17. 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)

18. Use of Description Tools
The description tools are presented on the basis of the functionality they provide.
In practice, they are combined into meaningful sets of description 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)

19. 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)

20. 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.

21. 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)

22. Low-level Features (types)
Basic
Basic Spectral
Signal Parameters
Timbral Temporal
Timbral Spectral
Spectral Basis
MPEG-7 Silence Descriptor

23. Low-level Features (graph)

24. Low-level Features (details)
Basic: (temporally sampled scalar values for general use)
AudioWaveform Descriptor
waveform envelope: (for display purposes).
AudioPower Descriptor
temporally-smoothed instantaneous power:
(quick summary of a signal)
Applicable to all kinds of signals

25. 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)

26. 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

27. Low-level Features (details)
Timbral Temporal: (temporal characteristics of segments of sounds, musical timbre)
LogAttackTime
TemporalCentroid
where in time the energy of a signal is focused.
Useful when attack times are identical

28. 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:
HarmonicSpectralCentroid
HarmonicSpectralDeviation
HarmonicSpectralSpread
HarmonicSpectralVariation

29. Low-level Features (details)
Spectral Basis: (low-dimensional projections of a spectral space to aid compactness and recognition)
AudioSpectrumBasis:
a series of (time-varying / statistically independent) basis functions derived 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.

30. 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

31. 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

32. High-level audio Description Tools (details)
Audio Signature Description Scheme
SpectralFlatness Ds
a unique content identifier for the purpose of robust automatic identification
e.g. audio fingerprinting

33. High-level audio Description Tools (details)
Musical Instrument Timbre Description Tools
HarmonicInstrumentTimbre Ds:
LogAttackTime Descriptor
PercussiveIinstrumentTimbre Ds:
SpectralCentroid Descriptor

34. High-level audio Description Tools (details)
Melody Description Tools:
efficient, robust, and expressive melodic similarity matching.
MelodyContour Description Scheme:
terse, efficient melody contour / rhythm
MelodySequence Description Scheme:
verbose, complete, expressive melody / rhythm.
Interval encoding

35. High-level audio Description Tools (details)
General Sound Recognition and Indexing Description Tools:
SoundModel Description Scheme
SoundClassificationModel Description Scheme
a set of SoundModel DS -> multi-way classifier
SoundModelStatePath Descriptor
indices to states generated by a SoundModel of a segment
immediately applied to sound effects
automatically index and segment sound tracks.
Low -> mid -> high level analyses

36. 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

37. 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

38. 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

39. MPEG-7 work plan:
See :
Annex A of MPEG-7 Overview (version 9)

40. Annotated Link Page / References
All pictures taken from:
P. Salembier and O. Avaro, “MPEG-7: Multimedia Content Description interface”,