code: private HeaderBitField createHeaderField() throws IOException {
          HeaderBitField field = new HeaderBitField();
          field.add(nextByte());
          field.add(nextByte());
          field.add(nextByte());
          return field;
      }
docs: Creates a bit field for the MPEG frame header.
  
  @return the bit field
  @throws IOException
  if an error occurs