Android AudioEffect浅谈

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转至：http://www.cnblogs.com/salam/archive/2011/01/09/1931241.html

在Android2.3中增加了对音频混响的支持，这些API包含在android.media.audiofx包中。　

　　一、概述

　　AudioEffect是android audio framework(android 音频框架)提供的音频效果控制的基类。开发者不能直接使用此类，应该使用它的派生类。　下面列出它的派生类。　

　　　　Equalizer
　　　　Virtualizer
　　　　BassBoost
　　　　PresetReverb
　　　　EnvironmentalReverb

　　当创建AudioEffect时，如果音频效果应用到一个具体的AudioTrack和MediaPlayer的实例，应用程序必须指定该实例的音频session ID，如果要应用Global音频输出混响的效果必须制定Session 0。

　　要创建音频输出混响(音频 Session 0)要求要有 MODIFY_AUDIO_SETTINGS权限。

　　如果要创建的效果在audio framework不存在，那么直接创建该效果，如果已经存在那么直接使用此效果。如果优先级高的对象要在低级别的对象使用该效果时，那么控制将转移到优先级高的对象上，否则继续停留在此对象上。在这种情况下，新的申请将被监听器通知。

　　二、嵌套类

　　1.AudioEffect.Descriptor：效果描述符包含在音频框架内实现某种特定的效果的信息。
　　2.AudioEffect.OnControlStatusChangeListener：此接口定义了当应用程序的音频效果的控制状态改变时由AudioEffect调用的方法。

　　3.AudioEffect.OnEnableStatusChangeListener：此接口定义了当应用程序的音频效果的启用状态改变时由AudioEffect调用的方法。

　　三、常量

StringACTION_CLOSE_AUDIO_EFFECT_CONTROL_SESSION关闭音频效果StringACTION_DISPLAY_AUDIO_EFFECT_CONTROL_PANEL启动一个音频效果控制面板UI。StringACTION_OPEN_AUDIO_EFFECT_CONTROL_SESSION打开音频效果。intALREADY_EXISTS内部操作状态。intCONTENT_TYPE_GAME当播放内容的类型是游戏音频时EXTRA_CONTENT_TYPE的值。intCONTENT_TYPE_MOVIE当播放内容的类型是电影时EXTRA_CONTENT_TYPE的值。intCONTENT_TYPE_MUSIC当播放内容的类型是音乐时EXTRA_CONTENT_TYPE的值。intCONTENT_TYPE_VOICE当播放内容的类型是话音时EXTRA_CONTENT_TYPE的值。 StringEFFECT_AUXILIARYEffect connection mode 是auxiliaryStringEFFECT_INSERTEffect connection mode 是insert.intERROR指示操作错误。intERROR_BAD_VALUE指示由于错误的参数导致的操作失败。intERROR_DEAD_OBJECT指示由于已关闭的远程对象导致的操作失败。intERROR_INVALID_OPERATION指示由于错误的请求状态导致的操作失败。intERROR_NO_INIT指示由于错误的对象初始化导致的操作失败。intERROR_NO_MEMORY指示由于内存不足导致的操作失败。StringEXTRA_AUDIO_SESSION包含使用效果的音频会话ID。StringEXTRA_CONTENT_TYPE指示应用程序播放内容的类型。StringEXTRA_PACKAGE_NAME包含调用应用程序的包名。intSUCCESS操作成功。

　　四、公有方法

AudioEffect.DescriptorgetDescriptor()

获取效果描述符。

booleangetEnabled()

返回效果的启用状态。

intgetId()

返回效果的标识符

booleanhasControl()

检查该AudioEffect 对象是否拥有效果引擎的控制。如果有，则返回true。

static Descriptor[]queryEffects()

查询平台上的所有有效的音频效果。

voidrelease()

释放本地AudioEffect资源。

voidsetControlStatusListener(AudioEffect.OnControlStatusChangeListener listener)

注册音频效果的控制状态监听器.当控制状态改变时AudioEffect发出通知。

voidsetEnableStatusListener(AudioEffect.OnEnableStatusChangeListener listener)

设置音频效果的启用状态监听器。当启用状态改变时AudioEffect发出通知。

intsetEnabled(boolean enabled)

Enable or disable the effect.

　　五、应用（此应用来自于SDK包）

　　1.新建项目

　　你或许已经发现在2.3的项目中比2.2多一个配置文件proguard.cfg，包含混淆所需的proguard脚本。

　　2.打开AndroidManifest.xml文件

　　添加权限“android.permission.RECORD_AUDIO”。

　　3.可视化工具类VisualizerView.java

　　　　　　　　效果图　　

　　4.Main.java

package com.wjq.audiofx;import android.app.Activity;import android.media.AudioManager;import android.media.MediaPlayer;import android.media.audiofx.Equalizer;import android.media.audiofx.Visualizer;import android.os.Bundle;import android.util.Log;import android.view.Gravity;import android.view.ViewGroup;import android.widget.LinearLayout;import android.widget.SeekBar;import android.widget.TextView;public class Main extends Activity {     private static final String TAG = "AudioFxDemo";        private static final float VISUALIZER_HEIGHT_DIP = 50f;        private MediaPlayer mMediaPlayer;        private Visualizer mVisualizer;        private Equalizer mEqualizer;        private LinearLayout mLinearLayout;        private VisualizerView mVisualizerView;        private TextView mStatusTextView;        @Override        public void onCreate(Bundle icicle) {            super.onCreate(icicle);            setVolumeControlStream(AudioManager.STREAM_MUSIC);            mStatusTextView = new TextView(this);            mLinearLayout = new LinearLayout(this);            mLinearLayout.setOrientation(LinearLayout.VERTICAL);            mLinearLayout.addView(mStatusTextView);            setContentView(mLinearLayout);            // Create the MediaPlayer            mMediaPlayer = MediaPlayer.create(this, R.raw.test_cbr);            Log.d(TAG, "MediaPlayer audio session ID: " + mMediaPlayer.getAudioSessionId());            setupVisualizerFxAndUI();            setupEqualizerFxAndUI();    // Make sure the visualizer is enabled only when you actually want to receive data, and    // when it makes sense to receive data.    mVisualizer.setEnabled(true);    // When the stream ends, we don't need to collect any more data. We don't do this in    // setupVisualizerFxAndUI because we likely want to have more, non-Visualizer related code    // in this callback.    mMediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {        public void onCompletion(MediaPlayer mediaPlayer) {            mVisualizer.setEnabled(false);        }    });    mMediaPlayer.start();    mStatusTextView.setText("Playing audio...");}private void setupEqualizerFxAndUI() {    // Create the Equalizer object (an AudioEffect subclass) and attach it to our media player,    // with a default priority (0).    mEqualizer = new Equalizer(0, mMediaPlayer.getAudioSessionId());    mEqualizer.setEnabled(true);    TextView eqTextView = new TextView(this);    eqTextView.setText("Equalizer:");    mLinearLayout.addView(eqTextView);    short bands = mEqualizer.getNumberOfBands();    final short minEQLevel = mEqualizer.getBandLevelRange()[0];    final short maxEQLevel = mEqualizer.getBandLevelRange()[1];    for (short i = 0; i < bands; i++) {        final short band = i;        TextView freqTextView = new TextView(this);        freqTextView.setLayoutParams(new ViewGroup.LayoutParams(                ViewGroup.LayoutParams.FILL_PARENT,                ViewGroup.LayoutParams.WRAP_CONTENT));        freqTextView.setGravity(Gravity.CENTER_HORIZONTAL);        freqTextView.setText((mEqualizer.getCenterFreq(band) / 1000) + " Hz");        mLinearLayout.addView(freqTextView);        LinearLayout row = new LinearLayout(this);        row.setOrientation(LinearLayout.HORIZONTAL);        TextView minDbTextView = new TextView(this);        minDbTextView.setLayoutParams(new ViewGroup.LayoutParams(                ViewGroup.LayoutParams.WRAP_CONTENT,                ViewGroup.LayoutParams.WRAP_CONTENT));        minDbTextView.setText((minEQLevel / 100) + " dB");        TextView maxDbTextView = new TextView(this);        maxDbTextView.setLayoutParams(new ViewGroup.LayoutParams(                ViewGroup.LayoutParams.WRAP_CONTENT,                ViewGroup.LayoutParams.WRAP_CONTENT));        maxDbTextView.setText((maxEQLevel / 100) + " dB");        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(                ViewGroup.LayoutParams.FILL_PARENT,                ViewGroup.LayoutParams.WRAP_CONTENT);        layoutParams.weight = 1;        SeekBar bar = new SeekBar(this);        bar.setLayoutParams(layoutParams);        bar.setMax(maxEQLevel - minEQLevel);        bar.setProgress(mEqualizer.getBandLevel(band));        bar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {            public void onProgressChanged(SeekBar seekBar, int progress,                    boolean fromUser) {                mEqualizer.setBandLevel(band, (short) (progress + minEQLevel));            }            public void onStartTrackingTouch(SeekBar seekBar) {}            public void onStopTrackingTouch(SeekBar seekBar) {}        });        row.addView(minDbTextView);        row.addView(bar);        row.addView(maxDbTextView);        mLinearLayout.addView(row);    }}private void setupVisualizerFxAndUI() {    // Create a VisualizerView (defined below), which will render the simplified audio    // wave form to a Canvas.    mVisualizerView = new VisualizerView(this);    mVisualizerView.setLayoutParams(new ViewGroup.LayoutParams(            ViewGroup.LayoutParams.FILL_PARENT,            (int)(VISUALIZER_HEIGHT_DIP * getResources().getDisplayMetrics().density)));    mLinearLayout.addView(mVisualizerView);    // Create the Visualizer object and attach it to our media player.    mVisualizer = new Visualizer(mMediaPlayer.getAudioSessionId());    mVisualizer.setCaptureSize(Visualizer.getCaptureSizeRange()[1]);    mVisualizer.setDataCaptureListener(new Visualizer.OnDataCaptureListener() {        public void onWaveFormDataCapture(Visualizer visualizer, byte[] bytes,                int samplingRate) {            mVisualizerView.updateVisualizer(bytes);        }        public void onFftDataCapture(Visualizer visualizer, byte[] bytes, int samplingRate) {}    }, Visualizer.getMaxCaptureRate() / 2, true, false);}@Overrideprotected void onPause() {    super.onPause();    if (isFinishing() && mMediaPlayer != null) {        mVisualizer.release();        mEqualizer.release();        mMediaPlayer.release();        mMediaPlayer = null;    }}}

 1 package com.wjq.audiofx; 2  3 import android.content.Context; 4 import android.graphics.Canvas; 5 import android.graphics.Color; 6 import android.graphics.Paint; 7 import android.graphics.Rect; 8 import android.view.View; 9 10 public class VisualizerView extends View {11 12        private byte[] mBytes;13         private float[] mPoints;14         private Rect mRect = new Rect();15 16         private Paint mForePaint = new Paint();17 18         public VisualizerView(Context context) {19             super(context);20             init();21         }22 23         private void init() {24             mBytes = null;25 26             mForePaint.setStrokeWidth(1f);27             mForePaint.setAntiAlias(true);28             mForePaint.setColor(Color.rgb(0, 128, 255));29         }30 31         public void updateVisualizer(byte[] bytes) {32             mBytes = bytes;33             invalidate();34         }35 36         @Override37         protected void onDraw(Canvas canvas) {38             super.onDraw(canvas);39 40             if (mBytes == null) {41                 return;42             }43 44             if (mPoints == null || mPoints.length < mBytes.length * 4) {45                 mPoints = new float[mBytes.length * 4];46             }47 48             mRect.set(0, 0, getWidth(), getHeight());49 50             for (int i = 0; i < mBytes.length - 1; i++) {51                 mPoints[i * 4] = mRect.width() * i / (mBytes.length - 1);52                 mPoints[i * 4 + 1] = mRect.height() / 253                         + ((byte) (mBytes[i] + 128)) * (mRect.height() / 2) / 128;54                 mPoints[i * 4 + 2] = mRect.width() * (i + 1) / (mBytes.length - 1);55                 mPoints[i * 4 + 3] = mRect.height() / 256                         + ((byte) (mBytes[i + 1] + 128)) * (mRect.height() / 2) / 128;57             }58 59             canvas.drawLines(mPoints, mForePaint);60         }61 62 }

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