Freeze the spectral amplitudes or frequencies, or both, at the times specified. Freezing both is equivalent to HOLD. Unlike HOLD, the frozen portions overwrite the original sound — the sound is not lengthened. With STEPFREEZE, the freezing occurs at regular time-intervals. There is also a time-domain FREEZE function FREEZEDELAY. FREEZE Freeze spectral amplitudes and/or frequencies at times specified. The frozen portions substitute for the original: the outfile is not lengthened. The modes do not always give the result you might expect: Mode 1 can appear to freeze frequency, not amplitude, whereas Mode 2 can appear to freeze amplitudes and not frequencies! (See USAGE below for an explanation by the author, Trevor Wishart.) MODES 1. Freeze amplitudes: frequency changes in the frozen portion are unaffected 2. Freeze frequencies: amplitude changes in the frozen portion are unaffected 3. Freeze amplitudes and frequencies. PARAMETER datafile
of
times
at
which
the
spectrum is frozen / unfrozen, where freeze times
are preceded by the markers:
'a' ='after this time': use window here as freeze window for spectrum after this time. 'b' ='before this time': use window here as freeze window for spectrum before this time. Range: 0- file-length
Example: Freeze at 2" and unfreeze at 4". 0.0 a2.0 4.0 STEPFREEZE Freeze/unfreeze spectrum at regular time-intervals, alternating between the two. With small timesteps, this produces a granulation or "sample-and-hold" effect. PARAMETER timestep:
the
time-period over which to freeze/unfreeze (secs.)
Can be small, but must be > two analysis frames (=windows?). NOTES Like HOLD, freezing is a way of stopping the continuous spectral evolution which normally takes place in a sound. The following comments for FREEZE apply to a sound with a static spectrum that has been glissandoed, so the spectral frequencies of the source are rising. The author (Trevor Wishart) notes: "Bear in mind that the PVOC does NOT capture the time-changing partials of the sound, but only a moment to moment snapshot of the sound, and the energy in each frequency band at that time." Mode 1 (freeze amp): the analysis channels "mostly each have very tiny frequency ranges, so if you freeze the amplitude inside a channel, you are effectively sustaining the small frequency band which that channel represents ... so you hear a sustain of the spectral frequencies with perhaps a little subtle internal gliding." Mode 2 (freeze freq): "the unexpected audible result is that the sound continues to glide upwards in frequency, as it is the changing AMPLITUDE of the channels which causes some to be emphasized more than others, channel amplitudes changing over time as the source glisses upwards, so we now still hear a gliss upwards, the internal details having been only subtly shifted." Mode 3 (freeze amp and freq): "is the only one which does what you might expect. In this case, both amplitude and frequency are frozen in time, so the output during the frozen portion has a static spectrum (no pitch motion)."
|