andeoid硬件解码学习 （二）

Finally, I must say, finally, we get low-level media APIs in Android, the Android hardware decoding and encoding APIs are finally available. It was a thing since Android 4.1 in Google IO 2012, but until now, when a new Android version 4.2 has been released, those low-level APIs are still too hard to use. There're so many Android vendors, we can't even get the same results from all Google's Nexus devices.

Despite the annoyings, I still tried these APIs and prayed them to get better in next Android release, and next Android release would swallow market quikly.

I just finished a simple video player with the combination of MediaExtractor and MediaCodec, you may find the full project from my Github.

private MediaExtractor extractor;
private MediaCodec decoder;
private Surface surface;

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) {
          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;
    }

    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();
}