MediaRecorder测量音量大小
MediaRecorder mMediaRecorder;int ratio = mMediaRecorder.getMaxAmplitude() / BASE;int db = 0;// 分贝 也可以理解为定义的音量大小if (ratio > 1)db = (int) (20 * Math.log10(ratio));//db就是我们需要取得的音量的值。//(int) (20 * Math.log10(ratio))振幅和音量大小的公式//BASE的值由自己测试获得，我是怎么获取这个值得呢？//开启麦克风，不对麦克风说话，而由周围噪声获取的值大概在300到600之间我取得是600这个基准值。一下是一部分应用的代码：
package com.taobao.baby.manager;import java.io.File;import java.io.IOException;import com.taobao.baby.R;import com.taobao.baby.util.Log;import android.media.MediaRecorder;import android.os.Handler;import android.widget.ImageView;/** * amr音频处理 ** @author hongfa.yy * @version 创建时间2012-11-21 下午4:33:28 */public class RecordManager {private final String TAG = "RecordManager";private MediaRecorder mMediaRecorder;public static final int MAX_LENGTH = 1000 * 60 * 10;// 最大录音时长1000*60*10;private File file;public RecordManager(File file,ImageView view) {this.file = file;this.view=view;}public RecordManager(File file) {this.file = file;}private long startTime;private long endTime;/** * 开始录音 使用amr格式 ** @param mRecAudioFile * 录音文件 * @return */public void startRecord() {// 开始录音/* ①Initial：实例化MediaRecorder对象 */if (mMediaRecorder == null)mMediaRecorder = new MediaRecorder();try {/* ②setAudioSource/setVedioSource */mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);// 设置麦克风/* * ②设置输出文件的格式：THREE_GPP/MPEG-4/RAW_AMR/Default THREE_GPP(3gp格式 * ，H263视频/ARM音频编码)、MPEG-4、RAW_AMR(只支持音频且音频编码要求为AMR_NB) */mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.AMR_NB);/* ②设置音频文件的编码：AAC/AMR_NB/AMR_MB/Default 声音的（波形）的采样 */mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);/* ③准备 */mMediaRecorder.setOutputFile(file.getAbsolutePath());mMediaRecorder.setMaxDuration(MAX_LENGTH);mMediaRecorder.prepare();/* ④开始 */mMediaRecorder.start();// AudioRecord audioRecord./* 获取开始时间* */startTime = System.currentTimeMillis();// pre=mMediaRecorder.getMaxAmplitude();updateMicStatus();Log.i("ACTION_START", "startTime" + startTime);} catch (IllegalStateException e) {Log.i(TAG,"call startAmr(File mRecAudioFile) failed!"+ e.getMessage());} catch (IOException e) {Log.i(TAG,"call startAmr(File mRecAudioFile) failed!"+ e.getMessage());}}/** * 停止录音 ** @param mMediaRecorder */public long stopRecord() {if (mMediaRecorder == null)return 0L;endTime = System.currentTimeMillis();Log.i("ACTION_END", "endTime" + endTime);mMediaRecorder.stop();mMediaRecorder.reset();mMediaRecorder.release();mMediaRecorder = null;Log.i("ACTION_LENGTH", "Time" + (endTime - startTime));return endTime - startTime;}private final Handler mHandler = new Handler();private Runnable mUpdateMicStatusTimer = new Runnable() {public void run() {updateMicStatus();}};/** * 更新话筒状态 分贝是也就是相对响度 分贝的计算公式K=20lg(Vo/Vi) Vo当前振幅值 Vi基准值为600：我是怎么制定基准值的呢？ 当20 * * Math.log10(mMediaRecorder.getMaxAmplitude() / Vi)==0的时候vi就是我所需要的基准值 * 当我不对着麦克风说任何话的时候，测试获得的mMediaRecorder.getMaxAmplitude()值即为基准值。 * Log.i("mic_", "麦克风的基准值：" + mMediaRecorder.getMaxAmplitude());前提时不对麦克风说任何话 */private int BASE = 600;private int SPACE = 300;// 间隔取样时间private ImageView view;private void updateMicStatus() {if (mMediaRecorder != null && view != null) {// int vuSize = 10 * mMediaRecorder.getMaxAmplitude() / 32768;int ratio = mMediaRecorder.getMaxAmplitude() / BASE;int db = 0;// 分贝if (ratio > 1)db = (int) (20 * Math.log10(ratio));switch (db / 4) {case 0:view.setImageBitmap(null);break;case 1:view.setImageResource(R.drawable.audio_recorder_volume_1);break;case 2:view.setImageResource(R.drawable.audio_recorder_volume_2);break;case 3:view.setImageResource(R.drawable.audio_recorder_volume_3);break;case 4:view.setImageResource(R.drawable.audio_recorder_volume_4);break;case 5:view.setImageResource(R.drawable.audio_recorder_volume_5);break;default:view.setImageResource(R.drawable.audio_recorder_volume_5);break;}mHandler.postDelayed(mUpdateMicStatusTimer, SPACE);/* * if (db > 1) { vuSize = (int) (20 * Math.log10(db)); Log.i("mic_", * "麦克风的音量的大小：" + vuSize); } else Log.i("mic_", "麦克风的音量的大小：" + 0); */}}}
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