               var sourceBufferAudio, sourceBufferVideo, expectedFirstSB, expectedSecondSB;
                          if (addAudioFirst) {
                              expectedFirstSB = sourceBufferAudio = mediaSource.addSourceBuffer(typeAudio);
                              expectedSecondSB = sourceBufferVideo = mediaSource.addSourceBuffer(typeVideo);
                          } else {
                              expectedFirstSB = sourceBufferVideo = mediaSource.addSourceBuffer(typeVideo);
             