Audio Oscillator CHOP
The Audio Oscillator CHOP generates sounds in three ways. It repeats common waveforms (sine, triangle), it generates white noise (a random number for each sample), or it repeats a prepared incoming audio clip of any duration. It outputs typically 44100 samples per second. In contrast, the LFO CHOP by default generates waves at lower frequencies and lower sample rates (60 samples/second), however both Audio Oscillator and LFO are interchangeable by changing their frequencies and sample rates.
When it is synthesizing tones from the basic waveforms, the Audio Oscillator CHOP steps through the waveform at a rate that depends on the Pitch Control input. By default, a Pitch Control of 0 gives a middle A at 440 Hz; a 1 gives 880 Hz; a -1 gives 220 Hz. Steps of 1 in Pitch Control are 1 octave apart. Steps of 1/12 (.08333) are 1 semitone apart.
The Audio Oscillator is roughly modelled after the APR 2600 voltage-controlled oscillator (VCO).
Up to three input CHOPs can be connected to the Audio Oscillator CHOP.
Pitch Control - The first (optional) input affects the pitch. Output channels are generated for each Pitch Control channel. When pitch control is 0, it outputs a wave at the base frequency (default 440 Hz at 44,100 samples per second). It is "logarithmic": By default, increasing the pitch control by 1 increases the pitch by 1 octave, by 2 it increases by 2 octaves (4 times the frequency).
Reset Pulse - The second (optional) input contains pulses that restart the oscillator from the beginning of the wave or the Playback Source. 0 in the input means "play the oscillator". 1 means "stop the oscillator and cue it at the start of the waveform or Playback Source".
Playback Source - The third (optional) input is a replacement of the waveform Type. It is a sound clip to play at a rate modified by the Pitch Control, and can contain any number of channels. These channels are generated for each Pitch Control channel. The waveform Type and the Base Frequency parameters are disabled.
If you plug any sound clip into the Audio Oscillator CHOP's Playback Source, and Pitch Control is a constant value of 0 of any duration, it will just repeat the Playback Source. If you feed a Wave CHOP as its Pitch Control, it will raise and lower the speed/pitch of the input.
The Audio Oscillator CHOP can serve as a general motion time-warper and repeater. If you put motion channels into the third input, you can control the time warp by feeding different Pitch Control curves. 0 pitch is normal speed, 1 is double speed.
Unlike the Wave CHOP, this is an iterating CHOP, that is, it steps through the waveform while the pitch changes. To see this effect, feed an LFO CHOP into the Audio Oscillator. Unlike the LFO CHOP, the Audio Oscillator CHOP is designed for audio frequencies.
Parameters - Waveform Page
wavetype - ⊞ - The shape of the waveform to repeat, unless overridden by the Playback Source:
sin- (-1 to 1)
normal- (0 to 1)
tri- (-1 to 1)
ramp- (0 to 1)
square- (-1 to 1)
pulse- (0 to 1)
- White Noise
whitenoise- Random samples between -1 and 1
frequency - The cycles per second when the Pitch Control is zero.
Units per Octave
octave - Amount that the Pitch Control needs to increase by to raise the pitch by one octave. The default of 1 means that Pitch Control of 1 raises the pitch by 1 octave. Units per Octave of .08333 means that a Pitch Control of 3 raises the pitch by a factor of 3 x .08333 (three semitones). This is suitable for using MIDI note numbers as pitch control.
offset - Values output from the CHOP can have an offset added to them.
amp - Values output from the CHOP can be scaled.
bias - Shape control for Triangle, Gaussian and Square waves. For triangle waves, it moves the peak. For square waves, it alters the width of the peak. Zero means no bias.
phase - A value of .5 is a phase shift of 180 degrees, or one half cycle.
Smooth Pitch Changes
smooth - If the Pitch Control channel input to the Audio Oscillator CHOP is rising and is running at the Touch default of 60 frames per second, then the pitch will hold for 1/60 second before stepping up for another 1/60 second. This is an audible step. With this option On, the pitch rises for every audio sample, giving perfectly smooth glissando at extra compute cost.
resetcondition - ⊞ - This menu determines how the Reset input triggers a reset of the channel(s).
- Off to On
offtoon- Channels are reset when the Reset input goes off to on.
- While On
on- Channels are reset when the Reset input goes on. The channel will hold the reset value until the input turns off.
- On to Off
ontooff- Channels are reset when the Reset input goes on to off.
- While Off
off- Channels are reset when the Reset input goes off. The channel will hold the reset value until the input turns on.
reset - This button resets the channel(s) to 0 when On.
resetpulse - Instantly resets the channel(s) to 0.
Parameters - Channel Page
rate - Set the sample rate of the CHOP in samples per second.
Parameters - Common Page
timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.
scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.
Sample Rate Match
srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.
- Resample At First Input's Rate
first- Use rate of first input to resample others.
- Resample At Maximum Rate
max- Resample to the highest sample rate.
- Resample At Minimum Rate
min- Resample to the lowest sample rate.
- Error If Rates Differ
err- Doesn't accept conflicting sample rates.
exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.
- DAT Table by Index
datindex- Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
- DAT Table by Name
datname- Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
- Channel Name is Path:Parameter
autoname- The channel is the full destination of where to export to, such has
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
- Input 0 -
- Input 1 -
- Input 2 -
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To pulse a parameter is to send it a signal from a CHOP or python or a mouse click that causes a new action to occur immediately. A pulse via python is via the
.pulse() function on a pulse-type parameter, such as Reset in a Speed CHOP. A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel.
samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.
A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.
A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.
Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.
Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.