Android提供了MediaPlayer播放器播放媒体文件，其实MediaPlyer只是对Android Media包下的MediaCodec和MediaExtractor进行了包装，方便使用。但是最好理解下Android媒体文件的解码，编码和渲染流程。
Shape Of My Heart.mp4
使用android.media包下的MediaCodec和MediaExtractor实现一个简单的视频解码渲染。
使用到了:
- MediaCodec:负责媒体文件的编码和解码工作，内部方法均为native
- MediaExtractor:负责将指定类型的媒体文件从文件中找到轨道，并填充到MediaCodec的缓冲区中
- AudioTrack:负责将解码之后的音频播放
- SurfaceView:展示解码之后的视频
视频被播放主要分为以下步骤:
- 将资源加载到extractor
- 获取视频所在轨道
- 设置extractor选中视频所在轨道
- 创将解码视频的MediaCodec，decoder
- 开始循环，直到视频资源的末尾
- 将extractor中资源以一个单位填充进decoder的输入缓冲区
- decoder将解码之后的视频填充到输出缓冲区
- decoder释放输出缓冲区的同时，将缓冲区中数据渲染到surface
音频的播放类似，只多了AudioTrack部分，少了渲染到surface部分。
MediaCodec.releaseOutputBuffer(int outputBufferIndex, boolean render);
播放的控制，视频和音频各自拥有一个Thread。
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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;
}
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VideoThread
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private class VideoThread extends Thread {
@Override
public void run() {
MediaExtractor videoExtractor = new MediaExtractor();
MediaCodec videoCodec = null;
try {
videoExtractor.setDataSource(filePath);
} catch (IOException e) {
e.printStackTrace();
}
int videoTrackIndex;
//获取视频所在轨道
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);
//视频长度: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;
}
//将资源传递到解码器
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, "解码当前帧超时");
break;
case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
//outputBuffers = videoCodec.getOutputBuffers();
Log.v(TAG, "output buffers changed");
break;
default:
//直接渲染到Surface时使用不到outputBuffer
//ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
//延时操作
//如果缓冲区里的可展示时间>当前视频播放的进度，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 while
videoCodec.stop();
videoCodec.release();
videoExtractor.release();
}
}
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获取指定类型媒体文件所在轨道
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//获取指定类型媒体文件所在轨道
private int getMediaTrackIndex(MediaExtractor videoExtractor, String MEDIA_TYPE) {
int trackIndex = -1;
for (int i = 0; i < videoExtractor.getTrackCount(); i++) {
//获取视频所在轨道
MediaFormat mediaFormat = videoExtractor.getTrackFormat(i);
String mime = mediaFormat.getString(MediaFormat.KEY_MIME);
if (mime.startsWith(MEDIA_TYPE)) {
trackIndex = i;
break;
}
}
return trackIndex;
}
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将缓冲区传递至解码器
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//将缓冲区传递至解码器
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;
}
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音频的部分类似，完整源码请移步jiyangg/MediaPlaySimpleDemo
