<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>tablewa</title>
<link rel="stylesheet" type="text/css" href="csound.css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.76.1" />
<link rel="home" href="index.html" title="The Canonical Csound Reference Manual" />
<link rel="up" href="OpcodesTop.html" title="Orchestra Opcodes and Operators" />
<link rel="prev" href="tablew.html" title="tablew" />
<link rel="next" href="tablewkt.html" title="tablewkt" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">tablewa</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="tablew.html">Prev</a> </td>
<th width="60%" align="center">Orchestra Opcodes and Operators</th>
<td width="20%" align="right"> <a accesskey="n" href="tablewkt.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="refentry" title="tablewa">
<a id="tablewa"></a>
<div class="titlepage"></div>
<a id="IndexTablewa" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">tablewa</span>
</h2>
<p>tablewa —
Writes tables in sequential locations.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp47998096"></a>
<h2>Description</h2>
<p>
This opcode writes to a table in sequential locations to and from an a-rate variable. Some thought is required before using it. It has at least two major, and quite different, applications which are discussed below.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp47998920"></a>
<h2>Syntax</h2>
<pre class="synopsis">kstart <span class="command"><strong>tablewa</strong></span> kfn, asig, koff</pre>
</div>
<div class="refsect1" title="Performance">
<a id="idp48034000"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>kstart</em></span> -- Where in table to read or write.
</p>
<p>
<span class="emphasis"><em>kfn</em></span> -- i- or k-rate number of the table to read or write.
</p>
<p>
<span class="emphasis"><em>asig</em></span> -- a-rate signal to read from when writing to the table.
</p>
<p>
<span class="emphasis"><em>koff</em></span> -- i- or k-rate offset into table. Range unlimited - see explanation at end of this section.
</p>
<p>
In one application, it is intended to be used with one or with several <a class="link" href="tablera.html" title="tablera"><em class="citetitle">tablera</em></a> opcodes before a <span class="emphasis"><em>tablewa</em></span> -- all sharing the same <span class="emphasis"><em>kstart</em></span> variable.
</p>
<p>
These read from and write to sequential locations in a table at audio rates, with <span class="emphasis"><em>ksmps</em></span> floats being written and read each cycle.
</p>
<p>
<a class="link" href="tablera.html" title="tablera"><em class="citetitle">tablera</em></a> starts reading from location <span class="emphasis"><em>kstart</em></span>. <span class="emphasis"><em>tablewa</em></span> starts writing to location <span class="emphasis"><em>kstart</em></span>, and then writes to <span class="emphasis"><em>kstart</em></span> with the number of the location one more than the one it last wrote. (Note that for <span class="emphasis"><em>tablewa</em></span>, <span class="emphasis"><em>kstart</em></span> is both an input and output variable.) If the writing index reaches the end of the table, then no further writing occurs and zero is written to <span class="emphasis"><em>kstart</em></span>.
</p>
<p>
For instance, if the table's length was 16 (locations 0 to 15), and <span class="emphasis"><em>ksmps</em></span> was 5. Then the following steps would occur with repetitive runs of the <span class="emphasis"><em>tablewa</em></span> opcode, assuming that <span class="emphasis"><em>kstart</em></span> started at 0.
</p>
<div class="informaltable">
<table border="1">
<colgroup>
<col />
<col />
<col />
<col />
</colgroup>
<thead>
<tr>
<th>Run Number</th>
<th>Initial kstart</th>
<th>Final kstart</th>
<th>Locations Written</th>
</tr>
</thead>
<tbody>
<tr>
<td>1</td>
<td>0</td>
<td>5</td>
<td>0 1 2 3 4</td>
</tr>
<tr>
<td>2</td>
<td>5</td>
<td>10</td>
<td>5 6 7 8 9</td>
</tr>
<tr>
<td>3</td>
<td>10</td>
<td>15</td>
<td>10 11 12 13 14</td>
</tr>
<tr>
<td>4</td>
<td>15</td>
<td>0</td>
<td>15</td>
</tr>
</tbody>
</table>
</div>
<p>
This is to facilitate processing table data using standard a-rate orchestra code between the <a class="link" href="tablera.html" title="tablera"><em class="citetitle">tablera</em></a> and <span class="emphasis"><em>tablewa</em></span> opcodes. They allow all Csound k-rate operators to be used (with caution) on a-rate variables - something that would only be possible otherwise by <span class="emphasis"><em>ksmps</em></span> = 1, downsamp and upsamp.
</p>
<div class="caution" title="Several cautions" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Caution: Several cautions">
<tr>
<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Caution]" src="images/caution.png" />
</td>
<th align="left">Several cautions</th>
</tr>
<tr>
<td align="left" valign="top">
<p>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" type="disc">
<li class="listitem">
<p>
The k-rate code in the processing loop is really running at a-rate, so time dependent functions like <span class="emphasis"><em>port</em></span> and <span class="emphasis"><em>oscil</em></span> work faster than normal - their code is expecting to be running at k-rate.
</p>
</li>
<li class="listitem">
<p>
This system will produce undesirable results unless the <span class="emphasis"><em>ksmps</em></span> fits within the table length. For instance a table of length 16 will accommodate 1 to 16 samples, so this example will work with <span class="emphasis"><em>ksmps</em></span> = 1 to 16.
</p>
</li>
</ul>
</div>
<p>
</p>
</td>
</tr>
</table>
</div>
<p>
Both these opcodes generate an error and deactivate the instrument if a table with length < <span class="emphasis"><em>ksmps</em></span> is selected. Likewise an error occurs if <span class="emphasis"><em>kstart</em></span> is below 0 or greater than the highest entry in the table - if <span class="emphasis"><em>kstart</em></span> = table length.
</p>
<p>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" type="disc">
<li class="listitem">
<p>
<span class="emphasis"><em>kstart</em></span> is intended to contain integer values between 0 and (table length - 1). Fractional values above this should not affect operation but do not achieve anything useful.
</p>
</li>
<li class="listitem">
<p>
These opcodes are not interpolating, and the <span class="emphasis"><em>kstart</em></span> and <span class="emphasis"><em>koff</em></span> parameters always have a range of 0 to (table length - 1) - not 0 to 1 as is available in other table read/write opcodes. <span class="emphasis"><em>koff</em></span> can be outside this range but it is wrapped around by the final AND operation.
</p>
</li>
<li class="listitem">
<p>
These opcodes are permanently in wrap mode. When <span class="emphasis"><em>koff</em></span> is 0, no wrapping needs to occur, since the <span class="emphasis"><em>kstart</em></span>++ index will always be within the table's normal range. <span class="emphasis"><em>koff</em></span> not equal to 0 can lead to wrapping.
</p>
</li>
<li class="listitem">
<p>
The offset does not affect the number of read/write cycles performed, or the value written to <span class="emphasis"><em>kstart</em></span> by <span class="emphasis"><em>tablewa</em></span>.
</p>
</li>
<li class="listitem">
<p>
These opcodes cannot read or write the guardpoint. Use <span class="emphasis"><em>tablegpw</em></span> to write the guardpoint after manipulations have been done with <span class="emphasis"><em>tablewa</em></span>.
</p>
</li>
</ul>
</div>
<p>
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp48058888"></a>
<h2>Examples</h2>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
kstart <span class="op">=</span> 0
<span class="olabel">lab1:</span>
atemp <span class="opc">tablera</span> ktabsource, kstart, 0 <span class="comment">; Read 5 values from table into an</span>
<span class="comment">; a-rate variable.</span>
atemp <span class="op">=</span> <span class="opc">log</span>(atemp) <span class="comment">; Process the values using a-rate</span>
<span class="comment">; code.</span>
kstart <span class="opc">tablewa</span> ktabdest, atemp, 0 <span class="comment">; Write it back to the table</span>
<span class="octrl">if</span> ktemp 0 <span class="octrl">goto</span> <span class="olabel">lab1</span> <span class="comment">; Loop until all table locations</span>
<span class="comment">; have been processed.</span></pre>
</div>
<p>
</p>
<p>
The above example shows a processing loop, which runs every k-cycle, reading each location in the table <span class="emphasis"><em>ktabsource</em></span>, and writing the log of those values into the same locations of table <span class="emphasis"><em>ktabdest</em></span>.
</p>
<p>
This enables whole tables, parts of tables (with offsets and different control loops) and data from several tables at once to be manipulated with a-rate code and written back to another (or to the same) table. This is a bit of a fudge, but it is faster than doing it with k-rate table read and write code.
</p>
<p>
Another application is:
</p>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
kzero <span class="op">=</span> 0
kloop <span class="op">=</span> 0
kzero <span class="opc">tablewa</span> 23, asignal, 0 <span class="comment">; ksmps a-rate samples written</span>
<span class="comment">; into locations 0 to (ksmps -1) of table 23.</span>
<span class="olabel">lab1:</span> ktemp <span class="opc">table</span> kloop, 23 <span class="comment">; Start a loop which runs ksmps times,</span>
<span class="comment">; in which each cycle processes one of</span>
[ Some code to manipulate ] <span class="comment">; table 23's values with k-rate orchestra</span>
[ the value of ktemp. ] <span class="comment">; code.</span>
<span class="opc">tablew</span> ktemp, kloop, 23 <span class="comment">; Write the processed value to the table.</span>
kloop <span class="op">=</span> kloop <span class="op">+</span> 1 <span class="comment">; Increment the kloop, which is both the</span>
<span class="comment">; pointer into the table and the loop</span>
<span class="octrl">if</span> kloop <span class="op"><</span> ksmps <span class="octrl">goto</span> <span class="olabel">lab1</span> <span class="comment">; counter. Keep looping until all values</span>
<span class="comment">; in the table have been processed.</span>
asignal <span class="opc">tablera</span> 23, 0, 0 <span class="comment">; Copy the table contents back</span>
<span class="comment">; to an a-rate variable.</span></pre>
</div>
<p>
</p>
<p>
<span class="emphasis"><em>koff</em></span> -- This is an offset which is added to the sum of <span class="emphasis"><em>kstart</em></span> and the internal index variable which steps through the table. The result is then ANDed with the lengthmask (000 0111 for a table of length 8 - or 9 with guardpoint) and that final index is used to read or write to the table. <span class="emphasis"><em>koff</em></span> can be any value. It is converted into a long using the ANSI floor() function so that -4.3 becomes -5. This is what we would want when using offsets which range above and below zero.
</p>
<p>
Ideally this would be an optional variable, defaulting to 0, however with the existing Csound orchestra read code, such default parameters must be init time only. We want k-rate here, so we cannot have a default.
</p>
</div>
<div class="refsect1" title="Credits">
<a id="idp48079184"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Robin Whittle</td>
</tr>
<tr>
<td>Australia</td>
</tr>
</table>
<p>
</p>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="tablew.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="OpcodesTop.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="tablewkt.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">tablew </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> tablewkt</td>
</tr>
</table>
</div>
</body>
</html>
distrib
>
Mageia
>
5
>
x86_64
>
media
>
core-release
>
by-pkgid
>
b707d9a4ee443103660a75ccb6e51334
>
files
>
2703
