sah~
Sample and hold a signal
Description
Use sah~ to capture ("sample") and output ("hold") a value from an input signal whenever a trigger signal satisfies a threshold value according to one of several trigger conditions. The default trigger mode (Ascending) requires the signal to go from being at or below the threshold value to above it. At the moment the trigger condition is satisfied, the input signal is sampled and "held" until the trigger condition is satisfied again, at which point the input is sampled again. Generally this allows one signal to be synchronized to the behavior of another.
Arguments
initial-trigger-value[number]
optional
Initial trigger value
Attributes
duration[atom_long]: 0
Normally the signal output of sah~ remains constant. With a non-zero value for duration any new non-zero value will remain constant for a specified number samples, after which it will be 0.
thresh[float]: 0.
Sets the value of the trigger signal used to cause the input signal to be sampled and output.
triggermode[int]: 0
Determines how sah~ analyzes the trigger signal to cause the input to be sampled and output. The classic (and default) triggermode is 0 (Ascending).
Possible values:
0 = 'Ascending'
Ascending mode detects the trigger signal passing from below to above the threshold value. Useful with increasing ramps (such as phasor~ with a positive frequency).
1 = 'Descending'
Descending mode detects trigger signal passing from above to below the threshold value. Useful with decreating ramps (such as phasor~ with a negative frequency).
2 = 'Ascending or Descending'
Ascending + Descending mode detects trigger signal passing from below to above the threshold value or passing from above to below the threshold value. This mode may produce unexpected results with a phasor but might be more appropriate for a continuous trigger input such as a sine wave.
3 = 'Equals'
Equals mode detects an exact value in the trigger signal value. This mode is not recommended for continuous functions that may never reach a specific value, but could be useful to detect impulses or other signals where a specific value is expected.
4 = 'Zero-to-Nonzero'
Zero-to-Nonzero mode detects a trigger signal that goes from a zero value to a non-zero value. This could be useful to detect the start of a ramp or incoming audio. The value of thresh is ignored in this mode.
5 = 'Nonzero-to-Zero'
Nonzero-to-zero mode detects a trigger signal that goes from a non-zero value to a zero value. This could be useful to detect a signal turning off. The value of thresh is ignored in this mode.
6 = 'Phase'
Phase mode treats the threshold value as a phase value using the same phase detection algorithm as the what~ object. In Phase mode, sah~ detects resets in the output of the phasor~ object and defines those as triggers for a threshold value of 0. Phase mode works with both positive and negative phasor~ frequencies.
Common Box Attributes
annotation[symbol]
Sets the text that will be displayed in the Clue window when the user moves the mouse over the object.
background[int]: 0
Adds or removes the object from the patcher's background layer. background 1 adds the object to the background layer, background 0 removes it. Objects in the background layer are shown behind all objects in the default foreground layer.
color[4 floats]
Sets the color for the object box outline.
fontface[int]
Sets the type style used by the object. The options are:
plain
bold
italic
bold italic
Possible values:
0 = 'regular'
1 = 'bold'
2 = 'italic'
3 = 'bold italic'
fontname[symbol]
Sets the object's font.
fontsize[float]
Sets the object's font size (in points).
Possible values:
'8'
'9'
'10'
'11'
'12'
'13'
'14'
'16'
'18'
'20'
'24'
'30'
'36'
'48'
'64'
'72'
hint[symbol]
Sets the text that will be displayed in as a pop-up hint when the user moves the mouse over the object in a locked patcher.
ignoreclick[int]: 0
Toggles whether an object ignores mouse clicks in a locked patcher.
jspainterfile[symbol]
You can override the default appearance of a user interface object by assigning a JavaScript file with code for painting the object. The file must be in the search path.
patching_rect[4 floats]: 0. 0. 100. 0.
Sets the position and size of the object in the patcher window.
position[2 floats]
write-only
Sets the object's x and y position in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its size unchanged.
presentation[int]: 0
Sets whether an object belongs to the patcher's presentation.
presentation_rect[4 floats]: 0. 0. 0. 0.
Sets the x and y position and width and height of the object in the patcher's presentation, leaving its patching position unchanged.
rect[4 floats]
write-only
Sets the x and y position and width and height of the object in both patching and presentation modes (if the object belongs to its patcher's presentation).
size[2 floats]
write-only
Sets the object's width and height in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its position unchanged.
textcolor[4 floats]
Sets the color for the object's text in RGBA format.
textjustification[int]
Sets the justification for the object's text.
Possible values:
0 = 'left'
1 = 'center'
2 = 'right'
varname[symbol]
Sets the patcher's scripting name, which can be used to address the object by name in pattr, scripting messages to thispatcher, and the js object.
Messages
float
Set trigger threshold value
signal
In left inlet: A signal to be sampled. When the trigger signal (in the right inlet) satisfies the current trigger condition, the signal in the left inlet is sampled and its value is sent out as a constant signal value.
In right inlet: The trigger signal.
See Also
| Name | Description |
|---|---|
| gate~ | Route a signal to one of several outlets |
| phasor~ | Generate sawtooth signals |
| stash~ | Store and Recall Audio Signal Values |
| thresh~ | Detect signal above a set level |
| what~ | Generate Impulses for a List of Audio Values |