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outfile a binary formant file, which can be used in other formant applications
infile an analysis file
outfile a binary formant file
-f extract formant envelope 'linear frequency-wise', using 1 point for every N equally-spaced frequency-channels
-p extract formant envelope 'linear pitchwise', using N equally-spaced pitch-bands per octave
In earlier CDP systems this process was called SPECFGET. It is a straightforward utility to extract and store the evolving spectral envelope of a sound.
On Extracing Formants
The two extraction options (-fN |
-pN) relate to resolution. Essential information:
the logarithmic nature of the pitch scale means that as one
goes higher, an increasingly wider band of frequencies is encompassed
by the 'octave'. The octave of a tone is double that tone's frequency.
Thus the octave between 220Hz and 440Hz encompasses 220Hz, while the
octave between 2200Hz and 4400Hz encompasses 2200Hz.
With 'linear frequency-wise', the analysis channels define frequency bands of identical bandwidth: each band will encompass the same frequency range.
With 'linear pitchwise', the frequency bands actually get wider as one goes higher. For example, if linear pitchwise is set at N = 12, the octave between 220Hz and 440 Hz is divided into 12 semitones; if N = 3, the octave is divided into 4 minor thirds (each of slightly increasing bandwidth). In the octave between 2200Hz and 4400Hz these same divisions will consist in considerably wider bandwidths. In other words, linear pitchwise is working via ratios with the logarithmic relationship of pitches.
Linear frequency-wise should therefore be chosen if the main formant area of interest is in the higher frequencies, because there will be better resolution here when extracting the spectral envelope. But if the main interest in the sound is in the lower frequencies, then the linear pitchwise option will be suitable: the frequency bandwidths relate to the octave bandwidths. You are also able more easily to think in terms of normal musical terminology for intervals. If in doubt, you'll need to experiment.
| Linear frequency-wise | Linear pitchwise | |
|---|---|---|
| 'Equal' means: | frequency spacing is the same N = 2 | octave divisor is the same N = 12 |
| E.g., band is 220Hz | 86Hz (e.g,) encompassed by every 2 channels | 12 semitones within that octave |
| E.g., band is 2200Hz | exactly the same bandwidth | 12 semitones within that octave | Recommended application | better resolution with higher frequencies | effective with lower frequencies |
This process is essential when wanting to preseve the timbral qualities of a sound. They can be transferred to another sound, or they may be re-imposed on the original sound after it has undergone some other transformations. The re-imposing is done with FORMANTS PUT.
Also see FORMANTS PUT and FORMANTS GETSEE.
End of FORMANTS GET
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infile an analysis file
outsndfile a pseudo-soundfile file ready for viewing; do not resynthesize or play (an error message will be returned)
-fN extract formant envelope linear frequency-wise, using 1 point for every N equally-spaced frequency-channels
-pN extract formant envelope linear pitchwise, using N equally-spaced pitch-bands per octave
-s semitone bands for display (Default: equal Hz bands)
The resulting logarithmically scaled display indicates formant shapes, but NOT the absolute amplitude values.
See a detailed discussion of the two extraction options in the text for FORMANTS GET for further information on this choice.
Previously a part of SPECFSEE, this process produces a pseudo soundfile which can be viewed in the same way as a normal soundfile. In the display we see a series of spectral windows, separated by zeroes. The horizontal display represents the spectral frequencies and this may be displayed in a manner which increases regularly with frequency (linear frequency-wise) or in a manner which increases regularly with pitch (linear pitch-wise). The vertical display represents the amplitude of each spectral band. The range of amplitudes is very large indeed, and in order to display them in the soundfile format, the log of the amplitude values is used and scaled to utilise fully the range of sound-sample values (-32768 to 32767).
The display therefore indicates only the shape of the spectrum, and how that shape changes through time - no absolute amplitude values can be read off from it.
FORMNTS GETSEE uses linear interpolation in determining the spectral contour. The output pseudo-soundfile is viewed by loading it into a soundfile display program, such as CDP's VIEWSF.
SPECIAL NOTE – It is important to realise that output 'soundfile' is in this case a 'pseudo-soundfile'. All pseudo-soundfiles and binary files are displayed by DIRSF, and on PC are automatically given a .wav extension. It is therefore recommended that you adopt a naming convention that indicates which type of file it is, such as 'fmnt...' for the formant file produced by FORMANTS GET, 'psnd...' for the output of GETSEE, and 'bpdf...' for the binary pitch data file produced by PITCH. The different types of file all have their own 'property strings' written in the header, so the system will know what they are and prevent inappropriate use; the naming conventions are for your own convenience.
When a program produces a textfile, it is NOT given a .wav extension and will not be displayed by DIRSF. Look for textfiles in the current directory, with the command 'dir'.
Also see FORMANTS GET and FORMANTS PUT.
End of FORMANTS GETSEE
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infile and outfile PVOC analysis files
fmntfile a formant data file made with FORMANTS GET
outfile an analysis file ready for resynthesis
1 New formant envelope REPLACES the sound's own formant envelope
2 New formant envelope is IMPOSED ON TOP OF the sound's own formant envelope
-llof lof = low frequency, below which spectrum is set to zero
-hhif hif = high frequency, above which spectrum is set to zero
-ggain gain = adjustment to spectrum loudness (normally < 1.0)
-i quicksearch for formants (less accurate)
Previously SPECFPUT, FORMANTS PUT reads a spectral trajectory as stored in formant file and imposes it on infile. In many sounds, the amplitude peaks are focused around certain frequencies; these are called formant areas, and are a key factor in creating the timbral colouration of a sound. These formants may themselves change over time, forming a spectral trajectory. The spectral trajectory is extracted (prior to running FORMANTS PUT) with FORMANTS GET. This trajectory (i.e., spectral envelope) is the rising and falling amplitude pattern of the partials (frequencies).
When this pattern is imposed on another file, the precise spectral envelope changes and colourations are introduced into the receiving file.
The presence of the spectral trajectory data in the fmntfile makes it possible to impose the same data on more than one file.
There are several musical purposes which can be achieved with this
process:
End of FORMANTS PUT
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infile a binary formant data file created with FORMANTS GET
outsndfile a 'pseudo-soundfile' suitable for display in a graphic soundfile editor (do not resynthesize or play (an error message will be returned)
-v display data about formant-band parameters
The resulting logarithmically scaled display indicates formant shapes, but not the absolute amplitude values. This process used to form a part of the CDP program SPECFSEE. In the display we see a series of spectral windows, separated by zeroes. The horizontal display represents the spectral frequencies and this may be displayed in a manner which increases regularly with frequency (if linear frequency-wise was selected when using FORMANTS GET) or in a manner which increases regularly with pitch (if linear pitch-wise was selected).
The vertical display represents the amplitude of each spectral band. The range of amplitudes is very large indeed, and in order to display them in the soundfile format, the log of the amplitude value is used and scaled to utilise fully the range of sound-sample values (-32768 to 32767).
End of FORMANTS SEE
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infile and infile2 analysis files
outfile resultant analysis file
-fN extract formant envelope linear frequency-wise, using 1 point for every N equally spaced frequency channels
-pN extract formant envelope linear pitchwise, using N equally-spaced pitch-bands per octave
-llof lof is low frquency, below which data is filtered out
-hhif hif is high frquency, above which data is filtered out
-ggain gain is the amplitude adjustment to the signal (normally < 1.0)
FORMANTS VOCODE achieves 'cross-synthesis'; it was formerly called SPECVOCO, but here has been re-written extensively.
Cross-synthesis takes the time-evolving spectral envelope of one sound and imposes it on another sound. For example, vocal shouts will have a strong spectral profile. If this is imposed onto the sound of running water, we should hear the water shout.
Strictly speaking, this is not 'morphing', which is more of a gradual transition from one sound to another. But in a broader sense, it certainly is the reshaping of one sound with the characteristics of another.
The difference between frequency-wise and pitch-wise could be important. As discussed in FORMANTS GET above, linear frequency-wise divides into absolutely equal frequency bands, while linear pitchwise divides octaves (of varying frequency widths) into equal-ratio bands, but these bands will vary in size from octave to octave, wider as one goes higher. It was recommended above to use frequency-wise if the sound is concentrated in the higher frequency areas (to get better resolution), and pitchwise for lower frequency areas. Experimentation is still the name of the game.
Frequencies below lof and above hif are simply ignored when the new spectrum is reconstructed.
Gain is not predictable because it depends on the level of the signals you put in, their relative levels, and the way those levels are distributed over the spectrum. A process that boosts level a great deal at the low end of the spectrum can cause distortion. Try it with no gain first.
End of FORMANTS VOCODE
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cover things like formants, spectral envelope (comparing with the amplitude envelope), resolution, frequency bands, more on linear frequency-wise and linear pitchwise ...technical issues dealing with using formants, leaving the definitions of these terms to the glossary. Maybe a diagram illustrating freqwise & pitchwise and more detail on assessing what needs to be done with different types of sound.
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