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14<h1 align="left">AXRegisterExceedCallback</h1>
15
16<h2>Syntax</h2>
17<dl><dd><pre class="construction">
18#include &lt;revolution/ax.h&gt;
19
20typedef void (*AXExceedCallback)(u32 cycles);
21
22void AXRegisterExceedCallback(AXExceedCallback callback);
23</pre></dd></dl>
24
25<h2>Arguments</h2>
26<TABLE class="arguments" border="1" >
27  <tr>
28<th>callback</th>
29<td>Callback to be registered.</td>
30  </tr>
31</table>
32
33<h2>Return Values</h2>
34<p>None.</p>
35
36<h2>Description</h2>
37<p>The <CODE>AXRegisterExceedCallback</CODE> function registers the callback when the DSP audio process does not complete within the 3 ms audio frame.</p>
38
39<p>The AX library controls the DSP load dynamically so that the DSP audio process finishes within a single audio frame. However, in an 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>
40
41<p>The DSP load prediction of AX also presupposes that the audio data accessed by the DSP (such as parameter blocks) is placed in <CODE>MEM1</CODE>. Generally, <CODE>MEM2</CODE> has a slower access speed, compared to <CODE>MEM1</CODE>, so the placement of audio data in <CODE>MEM2</CODE> may result in a longer DSP processing time, compared to the AX estimate.</p>
42
43<p>When there is large number of simultaneously played voices and the 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>
44
45<p>The callback registered through this function will be called when there is a chance of such noise.</p>
46
47<p>Check the DSP processing time using this function when a noise is observed in the playback.</p>
48
49<p>The number of extra DSP cycles used over single audio frame is also passed to the callback <SPAN class="argument">cycles</SPAN> argument.</p>
50
51<h2>See Also</h2>
52<p>None.</p>
53
54<H2>Revision History</H2>
55<P>
562006/10/23 Initial version.<BR>
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