Android提供了MediaPlayer播放器播放媒體文件，其實MediaPlyer只是對Android Media包下的MediaCodec和MediaExtractor進行了包裝，方便使用。但是最好理解下Android媒體文件的解碼，編碼和渲染流程。

Shape Of My Heart.mp4

<source src="http://7xoquj.com1.z0.glb.clouddn.com/shape_of_my_heart.mp4" type="video/mp4">

使用android.media包下的MediaCodec和MediaExtractor實現一個簡單的視頻解碼渲染。

使用到了:

• MediaCodec:負責媒體文件的編碼和解碼工作，內部方法均為native
• MediaExtractor:負責將指定類型的媒體文件從文件中找到軌道，并填充到MediaCodec的緩沖區中
• AudioTrack:負責將解碼之后的音頻播放
• SurfaceView:展示解碼之后的視頻

視頻被播放主要分為以下步驟:

將資源加載到extractor

獲取視頻所在軌道

設置extractor選中視頻所在軌道

創將解碼視頻的MediaCodec，decoder

開始循環，直到視頻資源的末尾

將extractor中資源以一個單位填充進decoder的輸入緩沖區

decoder將解碼之后的視頻填充到輸出緩沖區

decoder釋放輸出緩沖區的同時，將緩沖區中數據渲染到surface

音頻的播放類似，只多了AudioTrack部分，少了渲染到surface部分。

MediaCodec.releaseOutputBuffer(int outputBufferIndex, boolean render);

• render為true就會渲染到surface

---

播放的控制，視頻和音頻各自擁有一個Thread。

public void play() {isPlaying = true;if (videoThread == null) {videoThread = new VideoThread();videoThread.start();}if (audioThread == null) {audioThread = new AudioThread();audioThread.start();}}public void stop() {isPlaying = false;}

VideoThread

private class VideoThread extends Thread {@Overridepublic void run() {MediaExtractor videoExtractor = new MediaExtractor();MediaCodec videoCodec = null;try {videoExtractor.setDataSource(filePath);} catch (IOException e) {e.printStackTrace();}int videoTrackIndex;//獲取視頻所在軌道videoTrackIndex = getMediaTrackIndex(videoExtractor, "video/");if (videoTrackIndex >= 0) {MediaFormat mediaFormat = videoExtractor.getTrackFormat(videoTrackIndex);int width = mediaFormat.getInteger(MediaFormat.KEY_WIDTH);int height = mediaFormat.getInteger(MediaFormat.KEY_HEIGHT);//視頻長度:秒float time = mediaFormat.getLong(MediaFormat.KEY_DURATION) / 1000000;callBack.videoAspect(width, height, time);videoExtractor.selectTrack(videoTrackIndex);try {videoCodec = MediaCodec.createDecoderByType(mediaFormat.getString(MediaFormat.KEY_MIME));videoCodec.configure(mediaFormat, surface, null, 0);} catch (IOException e) {e.printStackTrace();}}if (videoCodec == null) {Log.v(TAG, "MediaCodec null");return;}videoCodec.start();MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();ByteBuffer[] inputBuffers = videoCodec.getInputBuffers(); // ByteBuffer[] outputBuffers = videoCodec.getOutputBuffers();boolean isVideoEOS = false;long startMs = System.currentTimeMillis();while (!Thread.interrupted()) {if (!isPlaying) {continue;}//將資源傳遞到解碼器if (!isVideoEOS) {isVideoEOS = putBufferToCoder(videoExtractor, videoCodec, inputBuffers);}int outputBufferIndex = videoCodec.dequeueOutputBuffer(videoBufferInfo, TIMEOUT_US);switch (outputBufferIndex) {case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:Log.v(TAG, "format changed");break;case MediaCodec.INFO_TRY_AGAIN_LATER:Log.v(TAG, "解碼當前幀超時");break;case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED://outputBuffers = videoCodec.getOutputBuffers();Log.v(TAG, "output buffers changed");break;default://直接渲染到Surface時使用不到outputBuffer//ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];//延時操作//如果緩沖區里的可展示時間>當前視頻播放的進度，就休眠一下sleepRender(videoBufferInfo, startMs);//渲染videoCodec.releaseOutputBuffer(outputBufferIndex, true);break;}if ((videoBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {Log.v(TAG, "buffer stream end");break;}}//end whilevideoCodec.stop();videoCodec.release();videoExtractor.release();}}

獲取指定類型媒體文件所在軌道

//獲取指定類型媒體文件所在軌道private int getMediaTrackIndex(MediaExtractor videoExtractor, String MEDIA_TYPE) {int trackIndex = -1;for (int i = 0; i < videoExtractor.getTrackCount(); i++) {//獲取視頻所在軌道MediaFormat mediaFormat = videoExtractor.getTrackFormat(i);String mime = mediaFormat.getString(MediaFormat.KEY_MIME);if (mime.startsWith(MEDIA_TYPE)) {trackIndex = i;break;}}return trackIndex;}

將緩沖區傳遞至解碼器

//將緩沖區傳遞至解碼器private boolean putBufferToCoder(MediaExtractor extractor, MediaCodec decoder, ByteBuffer[] inputBuffers) {boolean isMediaEOS = false;int inputBufferIndex = decoder.dequeueInputBuffer(TIMEOUT_US);if (inputBufferIndex >= 0) {ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];int sampleSize = extractor.readSampleData(inputBuffer, 0);if (sampleSize < 0) {decoder.queueInputBuffer(inputBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);isMediaEOS = true;Log.v(TAG, "media eos");} else {decoder.queueInputBuffer(inputBufferIndex, 0, sampleSize, extractor.getSampleTime(), 0);extractor.advance();}}return isMediaEOS;}

音頻的部分類似，完整源碼請移步jiyangg/MediaPlaySimpleDemo

轉載于:https://www.cnblogs.com/jiy-for-you/p/7282033.html

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