Android音频播放（本地/网络）绘制数据波形，根据特征有节奏的改变颜色

ByteBuffer[] codecInputBuffers;
ByteBuffer[] codecOutputBuffers;

// 这里配置一个路径文件
extractor = new MediaExtractor();
try {
    extractor.setDataSource(this.mUrlString);
} catch (Exception e) {
    mDelegateHandler.onRadioPlayerError(MP3RadioStreamPlayer.this);
    return;
}

//获取多媒体文件信息
MediaFormat format = extractor.getTrackFormat(0);
//媒体类型
String mime = format.getString(MediaFormat.KEY_MIME);

// 检查是否为音频文件
if (!mime.startsWith("audio/")) {
    Log.e("MP3RadioStreamPlayer", "不是音频文件!");
    return;
}

// 声道个数：单声道或双声道
int channels = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
// if duration is 0, we are probably playing a live stream

//时长
duration = format.getLong(MediaFormat.KEY_DURATION);
// System.out.println("歌曲总时间秒:"+duration/1000000);

//时长
int bitrate = format.getInteger(MediaFormat.KEY_BIT_RATE);

// the actual decoder
try {
    // 实例化一个指定类型的解码器,提供数据输出
    codec = MediaCodec.createDecoderByType(mime);
} catch (IOException e) {
    e.printStackTrace();
}
codec.configure(format, null /* surface */, null /* crypto */, 0 /* flags */);
codec.start();
// 用来存放目标文件的数据
codecInputBuffers = codec.getInputBuffers();
// 解码后的数据
codecOutputBuffers = codec.getOutputBuffers();

// get the sample rate to configure AudioTrack
int sampleRate = format.getInteger(MediaFormat.KEY_SAMPLE_RATE);

// 设置声道类型:AudioFormat.CHANNEL_OUT_MONO单声道，AudioFormat.CHANNEL_OUT_STEREO双声道
int channelConfiguration = channels == 1 ? AudioFormat.CHANNEL_OUT_MONO : AudioFormat.CHANNEL_OUT_STEREO;
//Log.i(TAG, "channelConfiguration=" + channelConfiguration);

Log.i(LOG_TAG, "mime " + mime);
Log.i(LOG_TAG, "sampleRate " + sampleRate);

// create our AudioTrack instance
audioTrack = new AudioTrack(
        AudioManager.STREAM_MUSIC,
        sampleRate,
        channelConfiguration,
        AudioFormat.ENCODING_PCM_16BIT,
        AudioTrack.getMinBufferSize(
                sampleRate,
                channelConfiguration,
                AudioFormat.ENCODING_PCM_16BIT
        ),
        AudioTrack.MODE_STREAM
);

//开始play，等待write发出声音
audioTrack.play();
extractor.selectTrack(0);//选择读取音轨

// start decoding
final long kTimeOutUs = 10000;//超时
MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();

// 解码
boolean sawInputEOS = false;
boolean sawOutputEOS = false;
int noOutputCounter = 0;
int noOutputCounterLimit = 50;

while (!sawOutputEOS && noOutputCounter < noOutputCounterLimit && !doStop) {
    //Log.i(LOG_TAG, "loop ");
    noOutputCounter++;
    if (!sawInputEOS) {

        inputBufIndex = codec.dequeueInputBuffer(kTimeOutUs);
        bufIndexCheck++;
        // Log.d(LOG_TAG, " bufIndexCheck " + bufIndexCheck);
        if (inputBufIndex >= 0) {
            ByteBuffer dstBuf = codecInputBuffers[inputBufIndex];

            int sampleSize =
                    extractor.readSampleData(dstBuf, 0 /* offset */);

            long presentationTimeUs = 0;

            if (sampleSize < 0) {
                Log.d(LOG_TAG, "saw input EOS.");
                sawInputEOS = true;
                sampleSize = 0;
            } else {
                presentationTimeUs = extractor.getSampleTime();
            }
            // can throw illegal state exception (???)

            codec.queueInputBuffer(
                    inputBufIndex,
                    0 /* offset */,
                    sampleSize,
                    presentationTimeUs,
                    sawInputEOS ? MediaCodec.BUFFER_FLAG_END_OF_STREAM : 0);

            if (!sawInputEOS) {
                extractor.advance();
            }
        } else {
            Log.e(LOG_TAG, "inputBufIndex " + inputBufIndex);
        }
    }
    
    // decode to PCM and push it to the AudioTrack player
    // 解码数据为PCM
    int res = codec.dequeueOutputBuffer(info, kTimeOutUs);

    if (res >= 0) {
        //Log.d(LOG_TAG, "got frame, size " + info.size + "/" + info.presentationTimeUs);
        if (info.size > 0) {
            noOutputCounter = 0;
        }

        int outputBufIndex = res;
        ByteBuffer buf = codecOutputBuffers[outputBufIndex];

        final byte[] chunk = new byte[info.size];
        buf.get(chunk);
        buf.clear();
        if (chunk.length > 0) {
            //播放
            audioTrack.write(chunk, 0, chunk.length);

            //根据数据的大小为把byte合成short文件
            //然后计算音频数据的音量用于判断特征
            short[] music = (!isBigEnd()) ? byteArray2ShortArrayLittle(chunk, chunk.length / 2) :
                    byteArray2ShortArrayBig(chunk, chunk.length / 2);
            sendData(music, music.length);
            calculateRealVolume(music, music.length);

            if (this.mState != State.Playing) {
                mDelegateHandler.onRadioPlayerPlaybackStarted(MP3RadioStreamPlayer.this);
            }
            this.mState = State.Playing;
            hadPlay = true;
        }
        //释放
        codec.releaseOutputBuffer(outputBufIndex, false /* render */);
        if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
            Log.d(LOG_TAG, "saw output EOS.");
            sawOutputEOS = true;
        }
    } else if (res == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
        codecOutputBuffers = codec.getOutputBuffers();

        Log.d(LOG_TAG, "output buffers have changed.");
    } else if (res == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
        MediaFormat oformat = codec.getOutputFormat();

        Log.d(LOG_TAG, "output format has changed to " + oformat);
    } else {
        Log.d(LOG_TAG, "dequeueOutputBuffer returned " + res);
    }
}

Log.d(LOG_TAG, "stopping...");

relaxResources(true);

this.mState = State.Stopped;
doStop = true;

// attempt reconnect
if (sawOutputEOS) {
    try {
        if (isLoop || !hadPlay) {
            MP3RadioStreamPlayer.this.play();
        }
        return;
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

if (mBaseRecorder == null)
    return;

//获取音量大小
int volume = mBaseRecorder.getRealVolume();
//Log.e("volume ", "volume " + volume);

//缩减过滤掉小数据
int scale = (volume / 100);

//是否大于给定阈值
if (scale < 5) {
    mPreFFtCurrentFrequency = scale;
    return;
}

//这个数据和上个数据之间的比例
int fftScale = 0;
if (mPreFFtCurrentFrequency != 0) {
    fftScale = scale / mPreFFtCurrentFrequency;
}

//如果连续几个或者大了好多就可以改变颜色
if (mColorChangeFlag == 4 || fftScale > 10) {
    mColorChangeFlag = 0;
}

if (mColorChangeFlag == 0) {
    if (mColorPoint == 1) {
        mColorPoint = 2;
    } else if (mColorPoint == 2) {
        mColorPoint = 3;
    } else if (mColorPoint == 3) {
        mColorPoint = 1;
    }
    int color;
    if (mColorPoint == 1) {
        color = mColor1;
    } else if (mColorPoint == 2) {
        color = mColor3;
    } else {
        color = mColor2;
    }
    mPaint.setColor(color);
}
mColorChangeFlag++;
//保存数据
if (scale != 0)
    mPreFFtCurrentFrequency = scale;

...

/**
 * 此计算方法来自samsung开发范例
 *
 * @param buffer   buffer
 * @param readSize readSize
 */
protected void calculateRealVolume(short[] buffer, int readSize) {
    double sum = 0;
    for (int i = 0; i < readSize; i++) {
        // 这里没有做运算的优化，为了更加清晰的展示代码
        sum += buffer[i] * buffer[i];
    }
    if (readSize > 0) {
        double amplitude = sum / readSize;
        mVolume = (int) Math.sqrt(amplitude);
    }
}