1. Presentation on Timbre Similarity
Alexandre Savard
March 2006
Every one here is presenting a different kind of multimedia framework to be used in many different situations. As we think about…
Do we need an other One today???
During this presentation I will convince you that maybe we need an other one.
In fact I will convince you that mine is better

2. Content Introduction Measurement of timbre Measurement of similarity
Systems Evaluation
Recent developments
Conclusion
Stress a bit more on both background and motivation Definition of the Multimedia Framework
Gives us a better understanding of what is MPEG-21
Then I will make a nine parts overview of MPEG-21 before Concluding

3. Introduction Incomplete timbre definition
Timbre is a fundamental dimension of sound.
Timbre has been too often described as the
dimension of sound that lets the listener makes
distinction between two sounds that have the
same pitch and the same loudness.
May be there a kind of relation with the fact that those instrument are the most popular stringed one.
Two very interesting physics papers

4. Introduction Incomplete timbre definition
An efficient operational definition of timbre
haven’t been already achieved.
Previous research demonstrated the
multidimensional nature of timbre.
Existing timbre researches has already
compared the similarity of the timbre of
single instrumental notes.
May be there a kind of relation with the fact that those instrument are the most popular stringed one.
Two very interesting physics papers

5. Introduction Physical features of timbre Attack transients
Spectral flux
Spectral gravity centre
Harmonicity Ratio
Spectral/Temporal Envelope
Other factors:
Pitch
Loudness
DO the relation with
Less harmonics in high frequency sound.

6. Introduction Global Timbre
A local definition of timbre appears to be useless
for electronic music distribution development or
music recommendation systems.
Researches use the concept of “global” timbre that
attributes a timbre quality for an entire piece.
This idea only makes sense if there is only little
variations in texture and instrumentation.
Their haven’t been any research of practical use of timbre similarity other that in those fields

7. Measurement of timbre Mel-Frequency Cepstrum Coeficient
Mel-Frequency Cepstrum Coefficient (MFCC)
Spectral gravity centre
Spectral envelope
Spectral Flux
Combines those measures in a “feature vector”
Denis presentation shows an exemple We can clearly notice a
How recent development technologies push… of busines models The market is full of new access device. Usable
Physical goods
It is Clear that new model for distribution and trading digital content electronically are required.

8. Measurement of timbre Mel-Frequency Cepstrum Coefficient
It is a measure of the spectral envelope variations.
Consist of a mapping of the linear frequencies to
the psychoacoustically-based Mel scale.
It results an ordered sequence of coefficients.
Low-order coefficients describe slow temporal
changes of the spectral envelope.
High-order coefficients describe fast changes.
Octzave has the same distance

9. Measurement of Similarity
Similarity Metric
Metrics are applied to calculate the distance between
two representations and determine the similarity of
the music.
Should be related to strategy used by humans in
similarity judgments of timbre.
Denis presentation shows an exemple We can clearly notice a
How recent development technologies push… of busines models The market is full of new access device. Usable
Physical goods
It is Clear that new model for distribution and trading digital content electronically are required.

10. Measurement of Similarity
Gaussian Mixture Model
MFCC involves a large amount of coefficients.
It is necessary to get a more compact representation
to handle those results.
Here will be presented the discussion of gabriel weinreich’s paper on coupled piano string.
An interesting approach is to analyse the system in terms of its normal mode of vibration

11. Measurement of Similarity
Gaussian Mixture Model
GMM is composed of one or more components
Gaussian probability distributions.
Distance between GMM’s can be seen as a
measurement of the similarity.
Random probabilities are computed from each song
to be compared.
Samples are taken from both songs to be compared.
Here will be presented the discussion of gabriel weinreich’s paper on coupled piano string.
An interesting approach is to analyse the system in terms of its normal mode of vibration

12. Measurement of Similarity
Gaussian Mixture Model
“Distance” between GMM’s can be seen as a
measurement of the similarity.
“Distance” is the amount of necessary changes to
obtain samples of the second song from the first one.
The higher are those probabilities, the higher the
similarity is.
Here will be presented the discussion of gabriel weinreich’s paper on coupled piano string.
An interesting approach is to analyse the system in terms of its normal mode of vibration

13. Measurement of Similarity
Gaussian Mixture Model
Here will be presented the discussion of gabriel weinreich’s paper on coupled piano string.
An interesting approach is to analyse the system in terms of its normal mode of vibration
J. Aucouturier et al, 2004 “The Way It Sounds”: Timbre Models for Analysis
and Retrieval of Music Signals.

14. Measurement of Similarity
Different Approaches
Neural Networks
Hidden Markov Model
Gaussian Mixture Models
Self-Organizing Map
Because to describe the complete situation we need to add damping with the air damping in the string
It becomes quickly a mess.
Assingment #5 question 4.
Here will be presented the discussion of gabriel weinreich’s paper on coupled piano string.

15. Systems Evaluation Evaluation criteria
Timbre similarity judgment is based on a set of
objective and subjective perceptual, cognitive and
cultural aspects.
Measure are highly dependent of music present in
the database.
How do we judge that the algorithm is efficient wen people themselves don’t agree each others.

16. Systems Evaluation Objective Evaluation
The objective evaluation of timbral similarity
measure is problematic.
Metadatas of a given database include description
of the artist and of the genre. However, timbre
quality is not usually described in it.
How do we judge that the algorithm is efficient wen people themselves don’t agree each others.

17. Systems Evaluation Subjective Evaluation
Conducting a psychoacoustical survey
Deciding whether two songs have similar timbre
can be uncertain as it is an ill-defined concept.
How do we judge that the algorithm is efficient wen people themselves don’t agree each others.

18. Recent Developments Aucouturier and Pachet (2002)
Segmentation of each song using invariable 50 ms
windows.
Make use of a 8 coefficient MFCC to characterize
each segments.
Used Gaussian Mixture Model composed of three
Gaussian probability distribution.
100 random samples are taken for similarity
measurement.
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .

19. Aucouturier and Pachet (2002)
Recent Developments
Aucouturier and Pachet (2002)
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .
J. Aucouturier et al, 2004, “The Way It Sounds”: Timbre Models for Analysis
and Retrieval of Music Signals.

20. Recent Developments Aucouturier and Pachet (2004)
Finding the best set of parameters
Sampling rate of the music signal
Number of MFCCs extracted from each frame of data
Number of components used in the GMM
The distance sample rate to estimate the likelihood of one
model given another
Window size
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .

21. Aucouturier and Pachet (2004)
Recent Developments
Aucouturier and Pachet (2004)
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .
J. Aucouturier et al, 2004, “The Way It Sounds”: Timbre Models for Analysis
and Retrieval of Music Signals.

22. Recent Developments Aucouturier and Pachet (2004)
Alternative similarity measurements using Earth
Mover’s Distance and Hidden Markov Model.
Those techniques didn’t improved the
performances.
Bring the idea that there could exist a ceiling for
the performance of technique involving timbre
similarity.
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .

23. Recent Developments Liu and Huang (2000)
Developed an algorithm for singing voice.
Used MFCC as well as GMM for their timbre
representation.
The segmentation of audio signal is done according
to the phonemes in singing.
For a low admitance the bridge is harder to move, heavier mass
For a high admitance the bridge is easier to move, .

24. Recent Developments Logan and Salomon (2001)
Characterized timbre with MFCC.
Used K-means clustering instead of GMM.
Calculate the amount of similarity using Earth
Mover’s Distance.
The support here is the bridge in the case of a musical instrument.

25. Conclusion Denis presentation shows an exemple We can clearly notice a
How recent development technologies push… of busines models The market is full of new access device. Usable
Physical goods
It is Clear that new model for distribution and trading digital content electronically are required.

26. Bibliography
J. Aucouturier, F. Pachet, and Mark Sandler “The way it sounds”: Timbre models for analysis and retrieval of music signals. IEEE Transaction on multimedia.
J. Aucouturier, and F. Pachet Improving timbre similarity : How high’s the sky ? Proceedings of the International Conference on Music Information Retrieval.
J. Aucouturier, and F. Pachet Music similarity measures: What’s the use ?
Proceedings of the International Conference on Music Information Retrieval.
C. Liu, and C. Huang A singer identification technique for content-based classification of mp3 music object. Proceeding of the Conference on Information and Knowledge Management.
B. Logan, and A. Salomon A music similarity function based on signal analysis. Proceeding of the International Conference on Multimedia and Expo.
Denis presentation shows an exemple We can clearly notice a
How recent development technologies push… of busines models The market is full of new access device. Usable
Physical goods
It is Clear that new model for distribution and trading digital content electronically are required.