code: static void register(Transcoder transcoder) {
          Entry entry = makeEntry(transcoder.source, transcoder.destination);
          if (entry.transcoder != null)
              throw new TranscoderException(ErrorMessages.ERR_TRANSCODER_ALREADY_REGISTERED, new String(transcoder.source + " to "
                      + new String(transcoder.destination)));
          entry.transcoder = transcoder;
      }
docs: /* rb_register_transcoder