code: private void prepareThreadManager(StreamConfiguration sc) {
      assert(!flacStreamIsOpen);
      if(MAX_THREADED_FRAMES > 0) {
        threadManager = new BlockThreadManager(this);
        threadedFrames = new Frame[MAX_THREADED_FRAMES];
        for(int i = 0; i < MAX_THREADED_FRAMES; i++) {
          threadedFrames[i]  = new Frame(this.streamConfig);
          threadManager.addFrameThread(threadedFrames[i]);
        }
      }
      else {
        threadManager = null;
      }
    }
docs: Creates and configures a new BlockThreadManager if needed(or sets to null
  if threads turned off.) Method must only be called if flacStreamIsOpen
  equals false, and this must not change while executing this method.
  @param sc