Merge "MediaMuxer sample code update, no functional change" into jb-mr2-dev

 * It is generally used like this:

 *

 * <pre>

 * MediaMuxer muxer = new MediaMuxer(...);

 * MediaMuxer muxer = new MediaMuxer("temp.mp4", OutputFormat.MUXER_OUTPUT_MPEG_4);

 * // More often, the MediaFormat will be retrieved from MediaCodec.getOutputFormat()

 * // or MediaExtractor.getTrackFormat().

 * MediaFormat audioFormat = new MediaFormat(...);

 * MediaFormat videoFormat = new MediaFormat(...);

 * int audioTrackIndex = muxer.addTrack(audioFormat);

 * int videoTrackIndex = muxer.addTrack(videoFormat);

 * ByteBuffer inputBuffer = ByteBuffer.allocate(...);

 * ByteBuffer inputBuffer = ByteBuffer.allocate(bufferSize);

 * boolean finished = false;

 * BufferInfo bufferInfo = new BufferInfo();

 *

 * muxer.start();

 * while(inputBuffer has new data) {

 *   if (new data is audio sample) {

 *     muxer.writeSampleData(audioTrackIndex, inputBuffer, ...);

 *   } else if (new data is video sample) {

 *     muxer.writeSampleData(videoTrackIndex, inputBuffer, ...);

 *   }

 * while(!finished) {

 *   // getInputBuffer() will fill the inputBuffer with one frame of encoded

 *   // sample from either MediaCodec or MediaExtractor, set isAudioSample to

 *   // true when the sample is audio data, set up all the fields of bufferInfo,

 *   // and return true if there are no more samples.

 *   finished = getInputBuffer(inputBuffer, isAudioSample, bufferInfo);

 *   if (!finished) {

 *     int currentTrackIndex = isAudioSample ? audioTrackIndex : videoTrackIndex;

 *     muxer.writeSampleData(currentTrackIndex, inputBuffer, bufferInfo);

 *   }

 * };

 * muxer.stop();

 * muxer.release();

 * </pre>