Example Vocoder Waveforms

• Test Case
  • Two constant-amplitude sinusoids
  • Frequencies separated by 10 Hz (10 beats/sec)
• Vocoder Parameters
  • 2x time expansion
  • Vocoder frame size = 45ms 22 Hz
    (frame size half a beat pulse)
  • Vocoder hop size = 1/4 frame
    (Hanning or Hamming window)
• Vocoder Types
  • Classic Vocoder (Dan Ellis's Matlab Code)
  • Salsman's Phase-Locked Vocoder (Puckette, Laroche, Dolson)
  • SOLA-FS by Hejna and Musicus (Dan Ellis's Matlab Code)

• Phase is continuous across frames
• Relative phase not preserved across FFT bins

Amplitude envelope better preserved

• Time domain method
• Phase preserved within each frame
• Phase not continuous across frames, but frames cross-fade at ``best locations'' in time, based on maximum cross-correlation

---

Order a Hardcopy of Spectral Audio Signal Processing

Previous: Time-Scaling Phase Vocoder in Matlab
Next: References

---

written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.