Android 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;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		SurfaceView sv = new SurfaceView(this);
		sv.getHolder().addCallback(this);
		setContentView(sv);
	}

	protected void onDestroy() {
		super.onDestroy();
	}

	@Override
	public void surfaceCreated(SurfaceHolder holder) {
	}

	@Override
	public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
		if (mPlayer == null) {
			mPlayer = new PlayerThread(holder.getSurface());
			mPlayer.start();
		}
	}

	@Override
	public 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;
		}

		@Override
		public 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
							// dequeueOutputBuffer
							Log.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 fast
					while (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 now
				if ((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();
		}
	}
}

最后再奉上我修改过的代码，增加了选择文件的功能.

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

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