Android 新API 之 MediaCodec使用筆記

Android的視頻編解碼一直讓人有點糾結，SDK竟然不提供硬件編解碼的API，如果你想自己做，只能通過JNI藉助第三方編解碼器，其都是使用的軟解碼，效率很難保證，這對想做視頻通話的是一個不小的打擊。

好了，說到google 新提供的SDK中出現的類MediaCodec，這個api限制在API 16後，也就是Android 4.1.2後纔可以使用，如果你的系統低於這個版本，是不可以使用這個類的。MediaCodec這傢伙能提供給你硬件編解碼功能，當然得廠商支持在下層已經，如果廠商沒做好，系統會提供給你軟件編解碼器，反正不用你操心，可以直接就拿來用的。

使用網上有人提供的Demo，可以解碼mp4文件，具體情況還沒研究，先放出Github鏈接，直接自己抓出來就可以用，

如果懶得去抓，下面貼出代碼，就一個簡單的Activity，一切搞定，

“記得修改文件名，SAMPLE變量爲你自己的文件名稱”，

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

最近從事手機iOS/Android直播、視頻實時美顏方面的工作。

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