【Android 多媒體應用】使用MediaCodec解碼使用AudioTrack播放音頻數據

1.MainActivity.java

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

import java.io.IOException;

public class MainActivity extends Activity {

    private static final String SAMPLE = Environment.getExternalStorageDirectory() + "/test.aac";
    protected static AudioDecoderThread mAudioDecoder;
    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.play);
        mAudioDecoder = new AudioDecoderThread();
        btn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                try {
                    mAudioDecoder.startPlay(SAMPLE);
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        });

    }

    @Override
    protected void onStop() {
        super.onStop();
        mAudioDecoder.stop();
    }

}

2.AudioDecoderThread.java

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.media.MediaCodec;
import android.media.MediaCodec.BufferInfo;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.util.Log;

import java.io.IOException;
import java.nio.ByteBuffer;


public class AudioDecoderThread {
    private static final int TIMEOUT_US = 1000;
    private MediaExtractor mExtractor;
    private MediaCodec mDecoder;

    private boolean eosReceived;
    private int mSampleRate = 0;
    int channel = 0;
    private final String TAG = "AACPlay";
    public void startPlay(String path) throws IOException {
        eosReceived = false;
        //創建MediaExtractor對象用來解AAC封裝
        mExtractor = new MediaExtractor();
        try {
            //設置需要MediaExtractor解析的文件的路徑
            mExtractor.setDataSource(path);
        } catch (IOException e) {
            e.printStackTrace();
        }



            MediaFormat format = mExtractor.getTrackFormat(0);
            if (format == null)
            {
                Log.e(TAG,"format is null");
                return;
            }

            //判斷當前幀的文件類型是否為audio
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("audio/")) {
                Log.d(TAG, "format : " + format);
                //獲取當前幀的采樣率
                mExtractor.selectTrack(0);
                mSampleRate = format.getInteger(MediaFormat.KEY_SAMPLE_RATE);
                //獲取當前幀的通道數
                channel = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
                //音頻文件長度
                long duration = format.getLong(MediaFormat.KEY_DURATION);
                Log.d(TAG,"length:"+duration/1000000);
            }


        //創建MediaCodec對象
        mDecoder = MediaCodec.createDecoderByType(mime);
        //配置MediaCodec
        mDecoder.configure(format, null, null, 0);

        if (mDecoder == null) {
            Log.e(TAG, "Can't find video info!");
            return;
        }
        //啟動MediaCodec
        mDecoder.start();

        new Thread(AACDecoderAndPlayRunnable).start();
    }


    Runnable AACDecoderAndPlayRunnable = new Runnable() {

        @Override
        public void run() {
            AACDecoderAndPlay();
        }
    };


    public void AACDecoderAndPlay() {
        ByteBuffer[] inputBuffers = mDecoder.getInputBuffers();
        ByteBuffer[] outputBuffers = mDecoder.getOutputBuffers();

        BufferInfo info = new BufferInfo();

        int buffsize = AudioTrack.getMinBufferSize(mSampleRate, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT);
        // 創建AudioTrack對象
        AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, mSampleRate,
                AudioFormat.CHANNEL_OUT_STEREO,
                AudioFormat.ENCODING_PCM_16BIT,
                buffsize,
                AudioTrack.MODE_STREAM);
        //啟動AudioTrack
        audioTrack.play();

        while (!eosReceived) {
            int inIndex = mDecoder.dequeueInputBuffer(TIMEOUT_US);
            if (inIndex >= 0) {
                ByteBuffer buffer = inputBuffers[inIndex];
                //從MediaExtractor中讀取一幀待解數據
                int sampleSize = mExtractor.readSampleData(buffer, 0);
                if (sampleSize < 0) {
                    // We shouldn't stop the playback at this point, just pass the EOS
                    // flag to mDecoder, we will get it again from the
                    // dequeueOutputBuffer
                    Log.d(TAG, "InputBuffer BUFFER_FLAG_END_OF_STREAM");
                    mDecoder.queueInputBuffer(inIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);

                } else {
                    //向MediaDecoder輸入一幀待解碼數據
                    mDecoder.queueInputBuffer(inIndex, 0, sampleSize, mExtractor.getSampleTime(), 0);
                    mExtractor.advance();
                }
                //從MediaDecoder隊列取出一幀解碼后的數據
                int outIndex = mDecoder.dequeueOutputBuffer(info, TIMEOUT_US);
                switch (outIndex) {
                    case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                        Log.d(TAG, "INFO_OUTPUT_BUFFERS_CHANGED");
                        outputBuffers = mDecoder.getOutputBuffers();
                        break;

                    case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                        MediaFormat format = mDecoder.getOutputFormat();
                        Log.d(TAG, "New format " + format);
                        audioTrack.setPlaybackRate(format.getInteger(MediaFormat.KEY_SAMPLE_RATE));

                        break;
                    case MediaCodec.INFO_TRY_AGAIN_LATER:
                        Log.d(TAG, "dequeueOutputBuffer timed out!");
                        break;

                    default:
                        ByteBuffer outBuffer = outputBuffers[outIndex];
                        //Log.v(TAG, "outBuffer: " + outBuffer);

                        final byte[] chunk = new byte[info.size];
                        // Read the buffer all at once
                        outBuffer.get(chunk);
                        //清空buffer,否則下一次得到的還會得到同樣的buffer
                        outBuffer.clear();
                        // AudioTrack write data
                        audioTrack.write(chunk, info.offset, info.offset + info.size);
                        mDecoder.releaseOutputBuffer(outIndex, false);
                        break;
                }

                // 所有幀都解碼、播放完之后退出循環
                if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    Log.d(TAG, "OutputBuffer BUFFER_FLAG_END_OF_STREAM");
                    break;
                }
            }
        }

        //釋放MediaDecoder資源
        mDecoder.stop();
        mDecoder.release();
        mDecoder = null;

        //釋放MediaExtractor資源
        mExtractor.release();
        mExtractor = null;

        //釋放AudioTrack資源
        audioTrack.stop();
        audioTrack.release();
        audioTrack = null;
    }

    public void stop() {
        eosReceived = true;
    }

}

3.activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <Button
        android:id="@+id/play"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Play" />

</LinearLayout>