M. Dolson, "The phase vocoder: A tutorial," Computer Music J., vol. 10, no. 4, pp. 14--27, 1986.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....after the fact in the experiments we will present. The role of Synthesize is to play this recording back at variable rate (and without pitch change) so that the accompaniment follows the soloist. The variable playback rate is accomplished using a phase vocoder [Flanagan and Golden, 1966] [Dolson, 1986] . This technique begins by dividing the signal into a sequence of overlapping windows indexed by and computing the short time Fourier transform, for each window. Both the magnitude, T , and the phase difference between consecutive windows, U A CJ T WV A CJ T X) ....

M. Dolson. The phase vocoder: A tutorial. Computer Music Journal, 10(4):14--27, 1986.

....vary in time. Another important point is that their phases are recomputed from scratch and not given by analysis. The most famous analysis method for additive synthesis is probably the phase vocoder. Very good introductory texts on the phase vocoder can be found for example in [Moo78] Por80] [Dol86], or [Ser97a] It is mainly an implementation of the short time Fourier transform [All77] This section makes a short summary of the principles of this transformation and points out its main limitations. 3.1 Principles The Fourier transform converts the temporal signal (amplitude versus time) ....

M. Dolson. The Phase Vocoder: A Tutorial. Computer Music Journal, 10(4):14--27, 1986.

....at all. Concerning the processing speed, it should be able to apply the effect in real time, without any DSP or hardware add on. 2. Frame based frequency domain technique The technique used in this paper is a frame based frequency domain technique. It s based on the well known phase vocoder [GL84, D86, ML95] 2.1 General diagram In figure 1 we can see the general diagram, where the input is the audio signal and the output is the time scaled version of the input. First or all the input sound is windowed and goes through the FFT module to get the analysis frame (AF n ) with the spectrum amplitude ....

M. Dolson. "The phase vocoder: A tutorial". Computer Music Journal, 10(4):14-27, 1986.

....the speech recognizer. In order to improve the system s recognition performance on children s speech several methods for voice transformation were investigated. Two promising methods were chosen for implementation and evaluation. The first, method A, was inspired by the Phase Vocoder algorithm [10] and the second, method B, was inspired by the Time Domain PitchSynchronous Overlap Add (TD PSOLA) algorithm [11] Method B also included linear compression of the spectral envelope of each window to give some form of formant scaling possibility. A separate database was used for development ....

Dolson, M., "The phase vocoder: A tutorial" Computer Music Journal, vol. 10, no. 4, pp. 14-27, 1986.

....waveform is windowed by the function hn . Typically only the short time magnitude spectrum is considered in the time frequency representation. The short time phase spectrum is sometimes used to improve the frequency estimates in the time frequency representation of quasi harmonic sounds [9], but it is often omitted entirely, or used only in reconstruction [3] Time h(t) a) Time th(t) b) Time (c) dh dt (t) Figure 1: Window functions used by the three short time transforms used to compute reassigned times and frequencies. Waveform (a) is the original continuous time ....

Mark Dolson, "The phase vocoder: A tutorial," Computer Music Journal, vol. 10, no. 4, pp. 14 -- 27, 1986.

....vocoder, which uses a complex shorttime spectrum, thus preserving the phase information of the signal. The phase vocoder is implemented with a set of bandpass filters or with a short time Fourier transform. The phase vocoder allows time and pitch scale modifications, like the sinusoidal model does [Dolson 1986]. Source filter synthesis uses a time varying filter and an excitation signal, which is either a train of impulses or white noise. While the desired signal is obtained by filtering the broadband excitation, the method is also called subtractive synthesis. This method approximates human speech ....

Dolson, M. "The phase vocoder: a tutorial", Computer Music Journal 10(4), 1986.

....931 cue to instrument type than the steady state portion of a sound. Early work on additive synthesis modeling used painstaking hand analysis of spectra to trace out the relative strengths of harmonics of a complex sound [110] This approach was later replaced by automation with the phase vocoder [26], 72] which performs a similar task automatically and often generates a lower dimensional representation. Further refinements include sinusoidal analysis [66] which models a sound as the sum of a set of sinusoids whose amplitudes and frequencies vary in time. All of these methods generate ....

M. B. Dolson, "The phase vocoder: A tutorial," Comput. Music J., Winter 1986, pp. 14--27.

....bandwidth and the transformation modifies the phases of each sub band. 5. CLASSICAL PHASE VOCODER The principle of this technique is used, for example, in Super Vocodeur de Phase of the IRCAM in Paris, and in the phase vocoder of Daniel Arfib. It has been described in a lot of papers [6] [12]. A local spectrum is first calculated at different moments separated by an analysis constant step, and then, the output signal is resynthesized with a step according to the timemodification factor (which is the same as the pitch modification factor) Figure 2 shows an example of the slowing ....

M. B. Dolson, "The Phase Vocoder: A Tutorial", Computer Music J., vol.10(4), pp. 14-27, Win 1986.

....rather than the centre frequency of the channels, in order to obtain a more accurate estimate of frequency, and in turn allow a smaller window size to be used. This idea was first used in the phase vocoder of (Flanagan and Golden, 1966) and has since been used in many computer music applications (Dolson, 1986). The peaks in the power spectrum are then isolated by finding at each time point the local maxima in the frequency dimension which are above a minimum threshold and which contain at least 1 of the total power of the signal at that time, giving a set of atoms of energy localised in time and ....

Dolson, M. (1986). The phase vocoder: A tutorial.

....source parameters (voice pitch, noise level, etc. 2. 1 Spectral Subband Vocoders From the early legacy of speech signal processing came the powerful and flexible signal processing techniques known as the spectral subband vocoders (VOice CODERs) In the channel vocoder [1] and phase vocoder [2][3], the spectrum is broken into sections called subbands, and the information in each subband is analyzed. The analyzed parameters are then stored or transmitted for reconstruction at another time or physical site. The parametric data representing the information in each subband can be manipulated, ....

Dolson, M. 1986, "The Phase Vocoder: A Tutorial," Computer Music Journal, 10 (4), pp. 14-27.

....to achieve the same number of frequency bands (usually 12 or 24 per octave, corresponding to semitones or quartertones) The above approach is essentially that of the channel vocoder in speech analysis. An alternative approach which achieves much better resolution is based on the phase vocoder [9, 8]. The channel vocoder calculates the magnitude of the complex values returned by the Fourier transform, but ignores the phase information. This is justified by the observation that absolute phase does not appear to be relevant to the perception of sound. The idea of the phase vocoder is to use the ....

M. Dolson. The phase vocoder: A tutorial. Computer Music Journal, Volume 10, Number 4, pages 14--27, 1986.

....for each partial p there is a maximum in both DFT 0 and DFT 1 spectra for a certain index m p . Note that DFT 0 is the classic short time Fourier analysis, and using only DFT 0 leads to the classic phase vocoder. Very good introductory texts on this subject can be found for example in [6] [7], or [8] Approximate frequency and amplitude values are: f m R N p p 0 = 6) a DFT m p p 0 0 = 7) Taking advantage of DFT 1 , a much more accurate frequency value can be obtained using the equation: f DFT m DFT m p p p 1 1 0 1 2 = p [ 8) It is extremely ....

Mark B. Dolson. 1986. "The Phase Vocoder: A Tutorial". Computer Music Journal. Volume 10, Number 4, pp. 14-27.

.... since short time effects such as jitter have been shown to be important in distinguishing sources [McAd84] Such qualities should follow automatically from our perceptual modeling; we mention it specifically because it is a weakness of other representations such as the phase vocoder [Dols86] or the McAulay Quatieri Sinusoid Transform System [McAu86] The representation is intended to be invertible to a perceptually equivalent sound. This feature is particularly motivated by our goal of an ideal source separator as described below. It is a motive for homogeneity and against ....

M Dolson (1986) "The phase vocoder : a tutorial" Computer Music Journal 10(4)

....decomposition, is known as the phase vocoder . Its utility in speech compression and musical synthesis arises from the possibility that (in the case of speech and music) each filter output consists of a single component whose amplitude, frequency and phase vary only slowly over time. See [8, 4]. Power spectrum See spectrum . Discrete Fourier transform See Fourier analysis. Short time Fourier transform The Fourier transform as applied to a finite length sound signal. See Equation 1. These Fourier coefficients can be efficiently calculated using the fast Fourier transform (q.v. ....

....focused on extracting individual sinusoids from digital bandpass filters. In this case, the researchers relied on the boundedQ frequency transform , which is a short time (windowed) Fourier transform modified by relating the window length to the center frequency of the modulated filter. See [8] for a discussion of the interpretation of the short time Fourier transform as a modulated filter bank. The description of similar work at the same center in [18] 4 also referred to identification of filterbank output based on the bounded Q frequency transform as its primary spectral ....

M. Dolson. The phase vocoder: a tutorial. Computer Music Journal. Winter 1986, 10(4):14--27, 1986.

....not arise; and a means of phase locking adjacent channels of the resynthesis is proposed which alleviates the second one. 1. PHASE VOCODER The phase vocoder, first proposed by [Flanagan] was put into its modern, FFT based form by [Portnoff] and explored for musical applications by [Moorer] and [Dolson]. An incoming sampled signal x[n] is first analyzed using windowed DFTs. We will denote the results of this analysis by X[s;k] X[s;k] FT fw[n]x[n Gamma s]g[k] where w[n] is a windowing function and the DFT is taken as, FT fx[n]g[k] N Gamma1 X n=0 e Gamma2 ink=N x[n] We will ....

....that no more than one value for the integer p can give rise to an admissible frequency estimate. For Hamming or Hanning window functions we must have H N=4; for the Kaiser window function, H N=6. We now consider analysis resynthesis systems of the sort described in [Portnoff] Moorer] and [Dolson]. There, the output is synthesized by overlap adding IFFTs with a constant overlap, typically 4 or 8. We therefore wish to compute output spectra Y [u i ; k] for u i = 0; J; 2J; where J denotes the output hop size, usually N=4 or N=8. The algorithm is recursive; the ith output spectrum ....

Dolson, M., 1986. "The phase vocoder: a tutorial." Computer Music Journal, 10/4: pp. 14-26.

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M. Dolson, "The phase vocoder: A tutorial," Computer Music J., vol. 10, no. 4, pp. 14--27, 1986.

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M. Dolson, "The phase vocoder: A tutorial," Computer Music J., vol. 10, no. 4, pp. 14--27, 1986.

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M. Dolson. The phase vocoder: A tutorial. Computer Music J., vol. 10 (4), pp. 14-27, 1986.

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Mark Dolson, \The phase vocoder: A tutorial," Computer Music Journal, vol. 10, no. 4, pp. 14-27, Winter 1986.

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Dolson, M. "The Phase Vocoder: A Tutorial". Computer Music Journal, Vol. 10:4, pp. 14--27, Winter 1986.

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M. Dolson, "The phase vocoder: a tutorial," Computer Music Journal, 1986.

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Dolson, M.: The phase vocoder: A tutorial. Computer Music Journal 4 (1986) 14--27

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Mark Dolson, "The phase vocoder: A tutorial," Computer Music Journal, vol. 10, no. 4, pp. 14 -- 27, 1986.

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Dolson M (1986) The phase vocoder: a tutorial. Comput Music J 10(4):14-27

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M. Dolson "The Phase Vocoder: A Tutorial," Computer Music Journal, vol. 10 No. 4 Winter 1986, pp.14-27.

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