简介
MediaCodec:负责媒体文件的编码和解码工作，内部方法均为native方法。
正文
视频播放主要步骤如下：
- 将资源加载到MediaExtractor
- 获取视频所在轨道
- 设置MediaExtractor选中视频所在轨道
- 创建视频解码的MediaCodec
- 循环开始
- 将extractor中资源以一个单位填充到decorder的输入缓存区中
- decorder之后，将解码的视频填充到输出缓冲区中
- 将缓冲区中的数据渲染到surface中
- 循环结束，直至视频资源的末尾
- 释放资源
视频播放创建一个播放的Thread
private class PlayerThread extends Thread {
...
}
-
初始化
private MediaExtractor extractor;
private MediaCodec decoder;
extractor = new MediaExtractor();
ByteBuffer[] inputBuffers = decoder.getInputBuffers();
ByteBuffer[] outputBuffers = decoder.getOutputBuffers();
MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
2.将资源加载到MediaExtractor
try {
extractor.setDataSource(SAMPLE);
} catch (IOException e) {
e.printStackTrace();
}
3.获取视频所在轨道,设置MediaExtractor选中视频所在轨道,创建视频解码的MediaCodec
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);
try {
decoder = MediaCodec.createDecoderByType(mime);
} catch (IOException e) {
e.printStackTrace();
}
decoder.configure(format, surface, null, 0);
break;
}
}
4.循环操作：将extractor中资源以一个单位填充到decorder的输入缓存区中,decorder之后，将解码的视频填充到输出缓冲区中,将缓冲区中的数据渲染到surface中,循环结束，直至视频资源的末尾
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;
}
}
//将缓冲区中数据渲染到surface,render=true就会渲染到surface
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;
}
}
5.释放资源
decoder.stop();
decoder.release();
extractor.release();
总结
了解mediacodec和MediaExtractor的api和原理，按视频播放的步骤进行解码播放。
学习一步一个脚印，谢谢今天的自己。
