code: private void notifyBroadcastStart() {
          IStreamAwareScopeHandler handler = getStreamAwareHandler();
          if (handler != null) {
              try {
                  handler.streamBroadcastStart(this);
              } catch (Throwable t) {
                  log.error("Error in notifyBroadcastStart", t);
              }
          }
          // send metadata for creation and start dates
          IoBuffer buf = IoBuffer.allocate(256);
          buf.setAutoExpand(true);
          Output out = new Output(buf);
          out.writeString("onMetaData");
          Map<Object, Object> params = new HashMap<>();
          Calendar cal = GregorianCalendar.getInstance();
          cal.setTimeInMillis(creationTime);
          params.put("creationdate", ZonedDateTime.ofInstant(cal.toInstant(), ZoneId.of("UTC")).format(DateTimeFormatter.ISO_INSTANT));
          cal.setTimeInMillis(startTime);
          params.put("startdate", ZonedDateTime.ofInstant(cal.toInstant(), ZoneId.of("UTC")).format(DateTimeFormatter.ISO_INSTANT));
          if (log.isDebugEnabled()) {
              log.debug("Params: {}", params);
          }
          out.writeMap(params);
          buf.flip();
          Notify notify = new Notify(buf);
          notify.setAction("onMetaData");
          notify.setHeader(new Header());
          notify.getHeader().setDataType(Notify.TYPE_STREAM_METADATA);
          notify.getHeader().setStreamId(0);
          notify.setTimestamp(0);
          dispatchEvent(notify);
      }
docs: Notifies handler on stream broadcast start