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Fri Jul 22 14:38:17 2016 UTC (7 years, 8 months ago) by schoenebeck
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* NKSP: Updated behavior of wait() function.

1 <html>
2 <head>
3 <meta name="author" content="Christian Schoenebeck">
4 <title>wait() function</title>
5 <meta name="description" content="Pauses execution for a certain amount of time.">
6 </head>
7 <body>
8 <h1>wait()</h1>
9 <p>
10 Suspends / pauses execution of the current event handler instance for the requested
11 amount of microseconds. The paused event handler instance can also be resumed before
12 the requested amount times elapsed by calling <code lang="nksp">stop_wait()</code> from another
13 event handler instance.
14 </p>
15 <p>
16 The <code>??duration-us??</code> argument must neither
17 be negative nor zero, otherwise script execution will be aborted, because this
18 is a common indication of bugs in scripts which could potentially lead to
19 real-time instability or worse scenarios otherwise.
20 </p>
21 <note>
22 If the even handler instance's built-in variable <code>$NKSP_IGNORE_WAIT</code>
23 reflects <code>1</code> then all calls to <code>wait()</code> will be ignored.
24 This might for example be the case when <code>stop_wait()</code> with
25 <code>1</code> being passed to the 2nd argument of that function.
26 </note>
27
28 <h3>Function Prototype</h3>
29 <p/>
30 <code lang="nksp">
31 wait(??duration-us??)
32 </code>
33
34 <h3>Arguments</h3>
35 <table>
36 <tr>
37 <th>Argument Name</th> <th>Data Type</th> <th>Description</th>
38 </tr>
39 <tr>
40 <td><code>??duration-us??</code></td>
41 <td>Integer Number</td>
42 <td>Positive (non zero) amount of microseconds to pause execution.<br>
43 [required]</td>
44 </tr>
45 </table>
46
47 <h3>Return Value</h3>
48 <p>None.</p>
49
50 <h3>Examples</h3>
51 <p/>
52 <code>
53 on init
54 { The amount of notes to play }
55 declare const $delayNotes := 4
56 { Tempo with which the new notes will follow the orignal note }
57 declare const $bpm := 90
58 { Convert BPM to microseconds (duration between the notes) }
59 declare const $delayMicroSeconds := 60 * 1000000 / $bpm
60 { Just a working variable for being used with the while loop below }
61 declare polyphonic $i
62 { For each successive note we trigger, we will reduce the velocity a bit}
63 declare polyphonic $velocity
64 end on
65
66 on note
67 { First initialize the variable $i with 4 each time we enter this event
68 handler, because each time we executed this handler, the variable will be 0 }
69 $i := $delayNotes
70
71 { Loop which will be executed 4 times in a row }
72 while ($i)
73 { Calculate the velocity for the next note being triggered }
74 $velocity := 127 * $i / ($delayNotes + 1)
75 { Suspend this script for a short moment ... }
76 wait($delayMicroSeconds)
77 { ... and after that short break, trigger a new note. }
78 play_note($EVENT_NOTE, $velocity)
79 { Decrement loop counter $i by one }
80 $i := $i - 1
81 end while
82 end on
83 </code>
84
85 <note>
86 Using the <code>wait()</code> function can lead to concurrency issues with
87 regular variables, which are global variables by default. You might need
88 to use <a href="nksp.html#polyphonic_variables">polyphonic variables</a>
89 in such cases.
90 </note>
91
92 <note>
93 You need at least LinuxSampler 2.0.0.svn2 or higher for the
94 <code>wait()</code> function to fully work as expected. Versions
95 of LinuxSampler older than that will not resume the script at the
96 requested amount of time, instead those older version will resume
97 the script always at the beginning of the next audio fragment
98 cycle. So effectively a <code>wait()</code> call with a LinuxSampler
99 version older than 2.0.0.svn2 will pause your script for a few
100 miliseconds, no matter which function argument you provided.
101 </note>
102
103 </body>
104 </html>

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