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14<h1 align="left">AXRegisterExceedCallback</h1>
15
16
17<h2>C Specification</h2>
18<BLOCKQUOTE>
19<pre><code>#include &lt;revolution.h&gt;
20
21typedef void (*AXExceedCallback)(u32 cycles);
22void AXRegisterExceedCallback(AXExceedCallback callback);</code>
23</BLOCKQUOTE>
24
25<h2>Arguments</h2>
26
27<table border="1" cellpadding="3" cellspacing="0.1">
28  <tr>
29<td width="120" bgcolor="#ffffe8"><em><strong><code>callback </code></strong></em></td>
30    <td width="520">Callback to be registered.</td>
31  </tr>
32</table>
33
34<h2>Return Values</h2>
35
36<p>None.</p>
37
38<h2>Description</h2>
39
40<p><CODE>AXRegisterExceedCallback</CODE> function registers the callback that is called when the DSP audio process does not complete within the 3 millisecond audio frame.</p>
41
42<p>The AX library controls the DSP load dynamically so that the DSP audio process finishes within a single audio frame. However, in an actual application, complex memory access requests from multiple devices may cause latency in memory access, resulting in a longer DSP processing time compared to the DSP load estimate of AX.</p>
43
44<p>Also, the DSP load prediction of AX presupposes that the audio data accessed by the DSP (such as parameter blocks) is placed in MEM1. Generally, MEM2 has a slower access speed compared to MEM1, so the placement of audio data in MEM2 may result in a longer DSP processing time compared to the AX estimate.</p>
45
46<p>When there is large number of simultaneously played voices, and if the actual DSP processing time is longer than the AX forecast, the processing may not complete within a single audio frame. This in turn, may result in noise in the playback sound.</p>
47
48<p>The callback registered through this function will be called when there is a chance of such noise.</p>
49
50<p>Check the DSP processing time using this function when noise is observed during playback.</p>
51
52<p>On a related note, the number of extra DSP cycles used over single audio frame will be passed to the callback argument <code>cycles</code>.</p>
53
54<h2>See Also</h2>
55
56<H2>Revision History</H2>
57
58<P>2006/10/23 Initial version.</P>
59
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61<P>CONFIDENTIAL</p>
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