Android(安卓)新API 之 MediaCodec使用笔记

Android的视频编解码一直让人有点纠结，SDK竟然不提供硬件编解码的API，如果你想自己做，只能通过JNI借助第三方编解码器，其都是使用的软解码，效率很难保证，这对想做视频通话的是一个不小的打击。

好了，说到google 新提供的SDK中出现的类MediaCodec，这个api限制在API 16后，也就是Android 4.1.2后才可以使用，如果你的系统低于这个版本，是不可以使用这个类的。MediaCodec这家伙能提供给你硬件编解码功能，当然得厂商支持在下层已经，如果厂商没做好，系统会提供给你软件编解码器，反正不用你操心，可以直接就拿来用的。

使用网上有人提供的Demo，可以解码mp4文件，具体情况还没研究，先放出Github链接，直接自己抓出来就可以用，

如果懒得去抓，下面贴出代码，就一个简单的Activity，一切搞定，

“记得修改文件名，SAMPLE变量为你自己的文件名称”，

package io.vec.demo.mediacodec;import java.nio.ByteBuffer;import android.app.Activity;import android.media.MediaCodec;import android.media.MediaCodec.BufferInfo;import android.media.MediaExtractor;import android.media.MediaFormat;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.view.Surface;import android.view.SurfaceHolder;import android.view.SurfaceView;public class DecodeActivity extends Activity implements SurfaceHolder.Callback {private static final String SAMPLE = Environment.getExternalStorageDirectory() + "/video.mp4";private PlayerThread mPlayer = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);SurfaceView sv = new SurfaceView(this);sv.getHolder().addCallback(this);setContentView(sv);}protected void onDestroy() {super.onDestroy();}@Overridepublic void surfaceCreated(SurfaceHolder holder) {}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {if (mPlayer == null) {mPlayer = new PlayerThread(holder.getSurface());mPlayer.start();}}@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {if (mPlayer != null) {mPlayer.interrupt();}}private class PlayerThread extends Thread {private MediaExtractor extractor;private MediaCodec decoder;private Surface surface;public PlayerThread(Surface surface) {this.surface = surface;}@Overridepublic void run() {extractor = new MediaExtractor();extractor.setDataSource(SAMPLE);for (int i = 0; i < extractor.getTrackCount(); i++) {MediaFormat format = extractor.getTrackFormat(i);String mime = format.getString(MediaFormat.KEY_MIME);if (mime.startsWith("video/")) {extractor.selectTrack(i);decoder = MediaCodec.createDecoderByType(mime);decoder.configure(format, surface, null, 0);break;}}if (decoder == null) {Log.e("DecodeActivity", "Can't find video info!");return;}decoder.start();ByteBuffer[] inputBuffers = decoder.getInputBuffers();ByteBuffer[] outputBuffers = decoder.getOutputBuffers();BufferInfo info = new BufferInfo();boolean isEOS = false;long startMs = System.currentTimeMillis();while (!Thread.interrupted()) {if (!isEOS) {int inIndex = decoder.dequeueInputBuffer(10000);if (inIndex >= 0) {ByteBuffer buffer = inputBuffers[inIndex];int sampleSize = extractor.readSampleData(buffer, 0);if (sampleSize < 0) {// We shouldn't stop the playback at this point, just pass the EOS// flag to decoder, we will get it again from the// dequeueOutputBufferLog.d("DecodeActivity", "InputBuffer BUFFER_FLAG_END_OF_STREAM");decoder.queueInputBuffer(inIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);isEOS = true;} else {decoder.queueInputBuffer(inIndex, 0, sampleSize, extractor.getSampleTime(), 0);extractor.advance();}}}int outIndex = decoder.dequeueOutputBuffer(info, 10000);switch (outIndex) {case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:Log.d("DecodeActivity", "INFO_OUTPUT_BUFFERS_CHANGED");outputBuffers = decoder.getOutputBuffers();break;case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:Log.d("DecodeActivity", "New format " + decoder.getOutputFormat());break;case MediaCodec.INFO_TRY_AGAIN_LATER:Log.d("DecodeActivity", "dequeueOutputBuffer timed out!");break;default:ByteBuffer buffer = outputBuffers[outIndex];Log.v("DecodeActivity", "We can't use this buffer but render it due to the API limit, " + buffer);// We use a very simple clock to keep the video FPS, or the video// playback will be too fastwhile (info.presentationTimeUs / 1000 > System.currentTimeMillis() - startMs) {try {sleep(10);} catch (InterruptedException e) {e.printStackTrace();break;}}decoder.releaseOutputBuffer(outIndex, true);break;}// All decoded frames have been rendered, we can stop playing nowif ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {Log.d("DecodeActivity", "OutputBuffer BUFFER_FLAG_END_OF_STREAM");break;}}decoder.stop();decoder.release();extractor.release();}}}

最後再奉上我修改過的代碼，增加了選擇文件的功能.

http://download.csdn.net/detail/shawnkong/6555857

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