code: public OutputStream createOutputStream(Number streamId) {
          int channelId = getChannelIdForStreamId(streamId);
          if (log.isTraceEnabled()) {
              log.trace("Create output - stream id: {} channel id: {}", streamId, channelId);
          }
          final Channel data = getChannel(channelId++);
          final Channel video = getChannel(channelId++);
          final Channel audio = getChannel(channelId++);
          if (log.isTraceEnabled()) {
              log.trace("Output stream - data: {} video: {} audio: {}", data, video, audio);
          }
          return new OutputStream(video, audio, data);
      }
docs: Creates output stream object from stream id. Output stream consists of audio, video, and data channels.
  
  @see org.red5.server.stream.OutputStream
  @param streamId
  Stream id
  @return Output stream object