Welcome to the home page of Dr. Gianpaolo Evangelista,

Ph.D. - M.Sc. Electrical and Computing Eng., M.Sc. Physics

Professor of Music Informatics at mdw, Music and Performing Arts University, Vienna, Austria

G. Evangelista photoDispersive Warped Spectrogram

Previously

Interests

My research interests include all aspects of sound and music analysis, synthesis, coding and processing as applied, e.g., to electroacoustic and computer music, audio-visual and music production, sound engineering, multimedia, internet communication and hearing aids.

Research focuses on the following topics:

Current Research

(Click on each topic to see more details)

Warped Representations and Redressing

Signal representations are essential tools and paradigms for sound analysis and synthesis, audio processing, coding and music information retrieval. Popular examples are the STFT (Short-Time Fourier Transform) and the WT (Wavelet Transform), which lead to time-frequency and time-scale representations, respectively.

However, the definitions of the transforms and the underlying localization characteristics are often dictated by mathematical simplifications. For example, in the STFT, both time and frequency resolutions are constant or, in the simplest case of wavelet expansions, the frequency resolution is limited to one octave.

In order to incorporate physical or perceptual characteristics in the representation, essential to the valuable interpretation of the representative elements -- windowed sinusoids for the STFT and wavelets for the WT -- one can resort to domain mappings offered by time and frequency warping operators. In most cases, in order to preserve the perfect reconstruction properties of the transform, one desires to map any of the domains in a one-to-one fashion, so that information is preserved.

Third of octave warped windows In linear transforms, where the analysis process is accomplished by orthogonal signal projections (scalar products) over the representative elements, remapping the signal is equivalent to inverse mapping the representative elements. This results in a modification of the localization properties of the representative elements. This is exemplified in the figure, where the uniform frequency domain cosine window elements of STFT are mapped into windows having 1/3 octave frequency resolution.

While warping provides an effective method for designing the localization characteristics of the representation, unfortunately, it also affects the organization of the transform. For example, warping in frequency introduces dispersion in time, so that the time organization is disrupted in which the various frequency components are represented on a frequency dependent time axis.

In order to circumvent the problem of dispersion, we devised redressing methods consisting in further warping in the transform domain, described in recent papers found in the References.

Third of octave warped windows

The benefits of the method, when applied to a warped STFT achieving single tone resolution in a 12-tone scale bandwidth allocation, are shown in the figures. In the first figure (left), the non-uniform spectrogram of a short excerpt of music piece is computed using purely warped STFT is shown. In the next figure (right), the redressed spectrogram, with same frequency resolution, is shown. As one can see, in the redressed spectrogram one is able to follow the score of the piece.

References

Mejstrik T and Evangelista G (2016), "Estimates of the Reconstruction Error in Partially Redressed Warped Frames Expansions", In Proc. of Digital Audio Effect Conf. (DAFx'16). Brno, Czech Republic, September 2016, pp. 9-16.
BibTeX:
@inproceedings{MejEva16,
  author = {Thomas Mejstrik and Gianpaolo Evangelista},
  title = {Estimates of the Reconstruction Error in Partially Redressed Warped Frames Expansions},
  booktitle = {Proc. of Digital Audio Effect Conf. (DAFx'16)},
  year = {2016},
  pages = {9--16}
}
Evangelista G (2014), "Approximations for Online Computation of Redressed Frequency Warped Vocoders", In Proc. of Digital Audio Effect Conf. (DAFx'14). Erlangen, Germany, September 2014, pp. 85-91.
BibTeX:
@inproceedings{Eva14a,
  author = {Gianpaolo Evangelista},
  title = {Approximations for Online Computation of Redressed Frequency Warped Vocoders},
  booktitle = {Proc. of Digital Audio Effect Conf. (DAFx'14)},
  year = {2014},
  pages = {85--91}
}
Evangelista G, Dörfler M and Matusiak E (2013), "Arbitrary Phase Vocoders by means of Warping", Music / Technology. Vol. VII, pp. 91-118.
BibTeX:
@article{EvaDorMat13,
  author = {G. Evangelista and M. Dörfler and E. Matusiak},
  title = {Arbitrary Phase Vocoders by means of Warping},
  journal = {Music / Technology},
  year = {2013},
  volume = {VII},
  pages = {91--118}
}
Evangelista G (2013), "Warped Frames: dispersive vs. non-dispersive sampling", In Proceedings of the 10th Sound and Music Computing Conference. Stockholm, Sweden, August 2013, pp. 553-560. Logos Verlag Berlin.
BibTeX:
@inproceedings{Eva13,
  author = {Gianpaolo Evangelista},
  title = {Warped Frames: dispersive vs. non-dispersive sampling},
  booktitle = {Proceedings of the 10th Sound and Music Computing Conference},
  publisher = {Logos Verlag Berlin},
  year = {2013},
  pages = {553--560}
}
Evangelista G, Dörfler M and Matusiak E (2012), "Phase Vocoders With Arbitrary Frequency Band Selection", In Proceedings of the 9th Sound and Music Computing Conference. Copenhagen, Denmark, pp. 442-449.
BibTeX:
@inproceedings{EvaDoeMat12,
  author = {Gianpaolo Evangelista and Monika Dörfler and Ewa Matusiak},
  title = {Phase Vocoders With Arbitrary Frequency Band Selection},
  booktitle = {Proceedings of the 9th Sound and Music Computing Conference},
  year = {2012},
  pages = {442--449}
}
Evangelista G (2001), "Dyadic Warped Wavelets", Advances in Imaging and Electron Physics, April 2001. Vol. 117, pp. 73-171. Academic Press.
BibTeX:
@article{Eva01a,
  author = {G. Evangelista},
  title = {Dyadic Warped Wavelets},
  journal = {Advances in Imaging and Electron Physics},
  publisher = {Academic Press},
  year = {2001},
  volume = {117},
  pages = {73--171}
}
G. Evangelista and S. Cavaliere (1998), "Discrete Frequency Warped Wavelets: Theory and Applications", IEEE Trans. on Signal Processing., April, 1998. Vol. 46(4), pp. 874-885.
BibTeX:
@article{EvaCav98b,
  author = {G. Evangelista and S. Cavaliere},
  title = {Discrete Frequency Warped Wavelets: Theory and Applications},
  journal = {IEEE Trans. on Signal Processing},
  year = {1998},
  volume = {46},
  number = {4},
  pages = {874--885},
  note = {special issue on Theory and Applications of Filter Banks and Wavelets}
}
G. Evangelista and S. Cavaliere (1998), "Frequency Warped Filter Banks and Wavelet Transform: A Discrete-Time Approach Via Laguerre Expansions", IEEE Trans. on Signal Processing., October, 1998. Vol. 46(10), pp. 2638-2650.
BibTeX:
@article{EvaCav98a,
  author = {G. Evangelista and S. Cavaliere},
  title = {Frequency Warped Filter Banks and Wavelet Transform: A Discrete-Time Approach Via Laguerre Expansions},
  journal = {IEEE Trans. on Signal Processing},
  year = {1998},
  volume = {46},
  number = {10},
  pages = {2638--2650}
}

Wave Field Synthesis

Under construction animated-under-construction-image-0041

Physical Models of Musical Instruments: Guitar

Under construction animated-under-construction-image-0041


Current Teaching:

Current teaching is in the following programs at mdw University, IKE Institut (Institut für Komposition, Elektroaktustik und TonmeisterInnen-Ausbildung):

LCEM=Lehrgang für Computermusik und elektronische Medien (Course for Computer Music and Electronic Media)

TM=Tonmeister/-innenstudium (Sound Engineering Study Program).

 

Courses I teach in the respective programs:

Music Processing 1: Winter Semester: LCEM, TM

Music Processing 2: Summer Semester: LCEM, TM

Music Processing 3: Winter Semester: LCEM, TM

Music Processing 4: Summer Semester: LCEM, TM

Programming for Musicians 1: Winter Semester: LCEM, TM

Programming for Musicians 2: Summer Semester: LCEM, TM

 

Additional Future Teaching (in 2017-18):

Music Processing 5: Winter Semester: LCEM, TM

Music Processing 6: Summer Semester: LCEM, TM

 

Courses Contents:

Music Processing 1-6 Series

As a child I have always been curious about how toys worked and what was inside them.
So, after playing for a bit, I always tried to take them apart and see "inside".

Of course, this way, I destroyed a few of them but at the same time I learned a lot!
The real advancement was when I opened my toy electric guitar amplifier and changed some of the components at random, which I took from a broken TV set, to produce distortion: the sounds of the "cool" guitars...
This pushed me to learn practical electronics, and beyond, in order to build my own toys.

Today's electronic toys are most of the time less fun to hack on the hardware side. They are full of uninformative robot soldered chips; little or no access there, no.
However, the hacking has shifted to the software side, for which one must learn programming and a bit of math models in order to keep having fun...

The purpose of the Music Processing Series is to explore the main concepts and algorithms used in sound and music production by electronic means.

At production level we visit the main ideas in sound processing, analysis, synthesis and digital audio effects (what's inside them?).

For music composition, performance and representation we visit concepts in formal languages, information theory and music information retrieval, together with a bit of perception and cognition.

All this would not make sense without a sound computing environment which allows us to experiment with our own toys.
For the time being, this happens in SuperCollider...

The course is organized in front lectures, student's seminars, problem solving and projects.

Programming for Musicians 1-2 Series

This series is elective, so the content can be adjusted according to the interests of the students.
The idea is to either learn a new programming language and environment (such as PureData, Max/MSP, Octave-Matlab, etc.) or to brush up and improve previously acquired skills.

The course is organized in front lectures and student's exercises and projects.