Reference：https://github.com/ele828/blog/blob/master/source/_posts/Android%E5%B1%8F%E5%B9%95%E7%9B%B4%E6%92%AD%E6%96%B9%E6%A1%88.md

while (mIsCapturing) {
         // get encoded data with maximum timeout duration of TIMEOUT_USEC(=10[msec])
encoderStatus = mMediaCodec.dequeueOutputBuffer(mBufferInfo, TIMEOUT_USEC
 
);
            if (encoderStatus == MediaCodec.INFO_TRY_AGAIN_LATER) {
                // wait 5 counts(=TIMEOUT_USEC x 5 = 50msec) until data/EOS come

            } else if (encoderStatus == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
               if (DEBUG) Log.v(TAG, "INFO_OUTPUT_BUFFERS_CHANGED");
 
// this shoud not come when encoding
encoderOutputBuffers = mMediaCodec.getOutputBuffers();
} else if (encoderStatus == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
               if (DEBUG) Log.v(TAG, "INFO_OUTPUT_FORMAT_CHANGED");
// this status indicate the output format of codec is changed
                // this should come only once before actual encoded data
 
               // but this status never come on Android4.3 or less
               // and in that case, you should treat when MediaCodec.BUFFER_FLAG_CODEC_CONFIG come.
if (mMuxerStarted) {   // second time request is error
throw new RuntimeException("format changed twice");
}
            // get output format from codec and pass them to muxer
            // getOutputFormat should be called after INFO_OUTPUT_FORMAT_CHANGED otherwise crash.
final MediaFormat format = mMediaCodec.getOutputFormat(); // API >= 16
ByteBuffer spsb = format.getByteBuffer("csd-0");
ByteBuffer ppsb = format.getByteBuffer("csd-1");
            if (spsb != null) {
               byte[] sps = new byte[spsb.capacity()];
//spsb.position(4);
spsb.get(sps, 0, sps.length);
               try{
                  outputStream.write(sps);
//outputStream.write(pps);
}catch (IOException e){
                  e.printStackTrace();
}
            }
            if (ppsb != null) {
               byte[] pps = new byte[ppsb.capacity()];
ppsb.get(pps);
               try{
                  outputStream.write(pps);
//outputStream.write(pps);
}catch (IOException e){
                  e.printStackTrace();
}
            }mTrackIndex = muxer.addTrack(format);
mMuxerStarted = true;
                   if (!muxer.start()) {
                      // we should wait until muxer is ready
synchronized (muxer) {
                         while (!muxer.isStarted())
                  try {
                     muxer.wait(100);
} catch (final InterruptedException e) {
                     break LOOP;
}
                      }
                   }
            } else if (encoderStatus < 0) {
               // unexpected status
if (DEBUG) Log.w(TAG, "drain:unexpected result from encoder#dequeueOutputBuffer: " + encoderStatus);
} else {
                final ByteBuffer encodedData = encoderOutputBuffers[encoderStatus];
                if (encodedData == null) {
                   // this never should come...may be a MediaCodec internal error
throw new RuntimeException("encoderOutputBuffer " + encoderStatus + " was null");
}
                if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                   // You shoud set output format to muxer here when you target Android4.3 or less
                   // but MediaCodec#getOutputFormat can not call here(because INFO_OUTPUT_FORMAT_CHANGED don't come yet)
                   // therefor we should expand and prepare output format from buffer data.
                   // This sample is for API>=18(>=Android 4.3), just ignore this flag here
if (DEBUG) Log.d(TAG, "drain:BUFFER_FLAG_CODEC_CONFIG");
mBufferInfo.size = 0;
}

                if (mBufferInfo.size != 0) {
                   // encoded data is ready, clear waiting counter
count = 0;
                    if (!mMuxerStarted) {
                       // muxer is not ready...this will prrograming failure.
throw new RuntimeException("drain:muxer hasn't started");
}
                    // write encoded data to muxer(need to adjust presentationTimeUs.
byte[] outData = new byte[mBufferInfo.size];
encodedData.get(outData);
               try {
                  outputStream.write(outData,0,outData.length);
outputStream.flush();
} catch (IOException e) {
                  e.printStackTrace();
}
               mBufferInfo.presentationTimeUs = getPTSUs();
muxer.writeSampleData(mTrackIndex, encodedData, mBufferInfo);
prevOutputPTSUs = mBufferInfo.presentationTimeUs;
}
                // return buffer to encoder
mMediaCodec.releaseOutputBuffer(encoderStatus, false);
                if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                   // when EOS come.
mMuxerStarted = mIsCapturing = false;
               break;      // out of while
}
            }
        }//end while

將視訊資料流寫入檔案中，重點是H264的PPS和SPS部分，這部分在 MediaCodec.INFO_OUTPUT_FORMAT_CHANGED 裡面

通過獲得ByteBuffer，然後獲得csd-0和csd-1兩個部分，獲得最終的解碼資訊。之後再將視訊幀資料寫入檔案即可。

視訊播放器建議使用PotPlayer，完美播放H264檔案。