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SINUSOIDAL ADDITIVE SYNTHESIS

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CASTNESS '08 Audio Session. Piergiovanni Bazzana, ATMEL. Lorenzo Seno, Conservatorio de L'Aquila CRM, Roma. DIOPSIS AND SINUSOIDAL ADDITIVE SYNTHESIS ... – PowerPoint PPT presentation

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Title: SINUSOIDAL ADDITIVE SYNTHESIS


1
SINUSOIDAL ADDITIVE SYNTHESIS
  • using complex oscillators,based on DIOPSIS?

CASTNESS 08 Audio Session Piergiovanni
Bazzana, ATMEL Lorenzo Seno, Conservatorio de
LAquila CRM, Roma
2
Main music synthesis methods
  • Wavetables currently the most widely used.
  • The system is a (very clever) player of
    pre-recorded sounds.
  • The value is in the quality and extension of
    the database of records.
  • Many tricks are used in the art of making a
    wavetable based synth. Along with the recorded
    sounds, they make the sound of a given synth.
  • Frequency Modulation
  • Good at creating both harmonic and inharmonic
    sounds
  • The harmonic distribution is produced by
    modulating a simple sine wave signal with another
    sine wave. It is a nonlinear synthesis method
  • Well accepted and often used since the expiring
    of Stanford patent used by Yamaha
  • Physical modeling
  • The equations describing the behavior of a real
    instrument are computed
  • The quality of the result depends on the quality
    of the math model
  • Computing demanding. Not well accepted because
    past trials were done making too many trade-offs
    between quality and cost. DWG is an example

3
Main music synthesis methods
  • Subtractive
  • Starts from basic, harmonic rich oscillators
    (square, triangular), and filters it
  • The filters characteristic (e.g. cut-off) can be
    in turn modulated to produce dynamically changing
    sounds
  • Well suited for analogue synthesizers (e.g. Moog)
  • Additive
  • Superposition of tones based on Fourier analysis
  • The oscillators may be free or harmonically
    related
  • About one thousand of oscillators are required to
    create a realistic sound, as Karlheintz
    Stockhausen said in the 70s
  • Emphasis on computation
  • The demonstrator is based on ADDITIVE synthesis

4
ADDITIVE SYNTHESIS Sinusoidal Sinusoidal
oscillators modulated in amplitude and frequency,
of arbitrary frequency. Harmonic Amplitude
modulated oscillators, of harmonic
frequencies Example of harmonic synthesis FFT-1
(Rodet)

ANALYSIS Sinusoidal analisis McAuley-Quatieri H
armonic analisis via Vocoder

5
Why additive synthesis?
  • Real synthesis is performed, not just clever
    playing
  • Makes feasible accurate real time pitch shifting
    and time stretching
  • Not only temperated nor harmonic
  • Not only imitation of existing instruments it is
    possible to create new sounds by carving them in
    the time-frequency domain
  • Beyond the concept of musical instrument

A real time sinusoidal synthesizer is not only an
execution instrument it is a composition
instrument that can be parametrically and
algorithmically controlled in a very flexible and
complex way
6
FORMAT OF ANALYSIS DATA SDIF
SDIF Sound Description Interchange Format
http//www.cnmat.berkeley.edu/SDIF/
  • Supported Models
  • Fundamental Frequency Estimates
  • Discrete Short-Term Fourier Transform - DSTFT
  • Picked Spectral Peaks
  • Sinusoidal Tracks
  • Pseudo-harmonic Sinusoidal Tracks
  • Resonances / Exponentially Decaying Sinusoids
  • Time Domain Samples (PCM)

7
The basic Additive synthesis element COMPLEX
OSCILLATOR
There are about 14.000 cent in the audio band
8
The basic computing block of mAgic DSP
9
Main DIOPSIS? Demonstrator Features
  • Frames composed by 64-256 samples _at_ 48 KHz (1.3
    5.3 ms)
  • Constant frequency inside the frame
  • Interpolated Amplitude for continuity at frame
    borders
  • Frame by frame phase continuity

Pitch shifting All the frequencies are
multiplied by a constant factor ( 2 octaves in
principle) Time stretching The frame length is
changed (supported max stretching 2x 1/10
speed)
MIDI interface Note defines the amount of
pitch shift (the unity is the semi-tone)? Control
defines the time stretching Program definisce
the file to be played Control defines the speed
of portamento for the glissato. NoteON the
selected file is played Subsequent NoteON
without NoteOFF portamento to the new
pitch NoteOFF stops the play.
Supported models SDIFF Sinusoidal Models, Pseudo
Harmonic Models, Resonant Models, via
SDIFF file translation
Number of oscillators ?500 with the D740, ?1000
with the D940
10
Processing HW detail
11
New processing HW
12
Sinusoidal Synthesis and Diopsis? Architecture
  • HW support for complex operations
  • 1 Gflop real time synthesis of 1K oscillators
    (in C on the D940)
  • 40 bit floating point arithmetics provides max
    coherence and stability of computing algorithms
  • Typ Absorbtion 1W (fanless audio boards)
  • Tight integration between ARM (control and HMI)
    and DSP (massive computation)

13
A Demonstrator not a Synthesizer
  • Pitch shift w/o spectral/timbre reshaping
  • Pitch shift time stretching but without
    correlation with physical characteristics of real
    instruments
  • .
  • And so on

BUT. It plays nice sounds
14
Let listen them now !
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