ing elementary streams. Currently only supports an
 mp4 file as the output and at most one audio and/or one video elementary
 stream.
 <p>
 It is generally used like this:

 <pre>
 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