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am 688f4c58: Merge "Update java doc for visualizer FFT capture." into gingerbread

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* commit '688f4c58d4a7590ad47c219af3a5b8479d3a084d':
  Update java doc for visualizer FFT capture.
This commit is contained in:
Eric Laurent
2010-11-30 11:56:00 -08:00
committed by Android Git Automerger
parent 3a2dc0d573 688f4c58d4
commit 371ed72216
1 changed files with 38 additions and 8 deletions
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46
media/java/android/media/audiofx/Visualizer.java
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@@ -43,10 +43,8 @@ import android.os.Message;
* <li>Frequency data: 8-bit magnitude FFT by using the {@link #getFft(byte[])} method</li>
* </ul>
* <p>The length of the capture can be retrieved or specified by calling respectively
* {@link #getCaptureSize()} and {@link #setCaptureSize(int)} methods. Note that the size of the FFT
* is half of the specified capture size but both sides of the spectrum are returned yielding in a
* number of bytes equal to the capture size. The capture size must be a power of 2 in the range
* returned by {@link #getCaptureSizeRange()}.
* {@link #getCaptureSize()} and {@link #setCaptureSize(int)} methods. The capture size must be a
* power of 2 in the range returned by {@link #getCaptureSizeRange()}.
* <p>In addition to the polling capture mode described above with {@link #getWaveForm(byte[])} and
* {@link #getFft(byte[])} methods, a callback mode is also available by installing a listener by
* use of the {@link #setDataCaptureListener(OnDataCaptureListener, int, boolean, boolean)} method.
@@ -333,11 +331,43 @@ public class Visualizer {
}
}
/**
* Returns a frequency capture of currently playing audio content. The capture is a 8-bit
* magnitude FFT. Note that the size of the FFT is half of the specified capture size but both
* sides of the spectrum are returned yielding in a number of bytes equal to the capture size.
* {@see #getCaptureSize()}.
* Returns a frequency capture of currently playing audio content.
* <p>This method must be called when the Visualizer is enabled.
* <p>The capture is an 8-bit magnitude FFT, the frequency range covered being 0 (DC) to half of
* the sampling rate returned by {@link #getSamplingRate()}. The capture returns the real and
* imaginary parts of a number of frequency points equal to half of the capture size plus one.
* <p>Note: only the real part is returned for the first point (DC) and the last point
* (sampling frequency / 2).
* <p>The layout in the returned byte array is as follows:
* <ul>
* <li> n is the capture size returned by getCaptureSize()</li>
* <li> Rfk, Ifk are respectively the real and imaginary parts of the kth frequency
* component</li>
* <li> If Fs is the sampling frequency retuned by getSamplingRate() the kth frequency is:
* (k*Fs)/(n/2) </li>
* </ul>
* <table border="0" cellspacing="0" cellpadding="0">
* <tr><td>Index </p></td>
* <td>0 </p></td>
* <td>1 </p></td>
* <td>2 </p></td>
* <td>3 </p></td>
* <td>4 </p></td>
* <td>5 </p></td>
* <td>... </p></td>
* <td>n - 2 </p></td>
* <td>n - 1 </p></td></tr>
* <tr><td>Data </p></td>
* <td>Rf0 </p></td>
* <td>Rf(n/2) </p></td>
* <td>Rf1 </p></td>
* <td>If1 </p></td>
* <td>Rf2 </p></td>
* <td>If2 </p></td>
* <td>... </p></td>
* <td>Rf(n-1)/2 </p></td>
* <td>If(n-1)/2 </p></td></tr>
* </table>
* @param fft array of bytes where the FFT should be returned
* @return {@link #SUCCESS} in case of success,
* {@link #ERROR_NO_MEMORY}, {@link #ERROR_INVALID_OPERATION} or {@link #ERROR_DEAD_OBJECT}