1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
2<html>
3
4<head>
5<title>Utility Function</title>
6<LINK rel="stylesheet" type="text/css" href="../../CSS/revolution.css">
7<META http-equiv="Content-Type" content="text/html; charset=windows-1252">
8<META name="GENERATOR" content="IBM WebSphere Studio Homepage Builder Version 6.5.0.0 for Windows">
9<META http-equiv="Content-Style-Type" content="text/css">
10</head>
11
12<body>
13
14<h1 align="left">Utility Function</h1>
15
16<h2>Overview</h2>
17
18<p>The following utility functions have been prepared in the AX library.</p>
19
20<ul>
21<li>Function for calculating the low-pass filter coefficient.
22<li>Function for creating custom compressor tables.
23<li>Function for converting 16-bit PCM to DSP-ADPCM.
24<li>Function for converting DSP-ADPCM data to 16-bit PCM data.
25</ul>
26
27<H2>Calculating the Low-Pass Filter Coefficient</H2>
28
29<p>The <a href="AXGetLpfCoefs.html"><code>AXGetLpfCoefs</code></a> function has been prepared for calculating the low-pass filter coefficient to be set in the  <a href="../Parameter_Blocks/AXPBLPF_lpf.html"><code>AXPBLPF</code></a> structure as specified using the <a href="../Voice_Parameters/AXSetVoiceLpf.html"><code>AXSetVoiceLpf</code></a> or <a href="../Voice_Parameters/AXSetVoiceLpfCoefs.html"><code>AXSetVoiceLpfCoefs</code></a> function.</p>
30
31<p>A detailed description of the low-pass filter coefficient is included in the description of the <a href="../Parameter_Blocks/AXPBLPF_lpf.html"><code>AXPBLPF</code></a> structure.</p>
32
33<H2>Creating a Custom Compressor Table</H2>
34
35<p>The audio DSP compressor automatically applies an envelope to data to prevent noise when audio data in the mixing buffer exceeds the range of <code>s16</code>. A compressor table in the AX library defines the shape of this envelope.</p>
36
37<p>A custom compressor table of original shape can be created using the <a href="AXMakeCompressorTable.html"><code>AXMakeCompressorTable</code></a> function.</p>
38
39<p>The custom table created using the <a href="AXMakeCompressorTable.html"><code>AXMakeCompressorTable</code></a> function is registered in the AX library using the <a href="../Initialization/AXSetCompressorTable.html"><code>AXSetCompressorTable</code></a> function.</p>
40
41<H2>Converting from 16-bit PCM to DSP-ADPCM</H2>
42
43<p>The <a href="AXGetAdpcmData.html"><code>AXGetAdpcmData</code></a> function has been prepared so that the Wii can perform run-time conversion of 16-bit PCM data into ADPCM format for DSP (DSP-ADPCM).</p>
44
45<H2>Converting from DSP-ADPCM to 16-bit PCM</H2>
46
47<p>The <a href="AXDecodeAdpcmData.html"><code>AXDecodeAdpcmData</code></a> function allows you to use the Wii CPU to convert ADPCM-format data for the DSP (DSP-ADPCM) into 16-bit PCM data.</p>
48
49<h2>Revision History</h2>
50<P>
512008/12/17 Added information about DSP-ADPCM conversion functions.<br>2008/02/25 Added information on creating compressor tables and functions related to DSP-ADPCM conversion.<br>2007/10/02 Revised the entire document following changes to the structure of the function reference.<br>2006/XX/XX Initial version.
52</P>
53
54<hr><p>CONFIDENTIAL</p></body>
55</html>
56