code: public Number getStreamIdForChannelId(int channelId) {
          if (channelId < 4) {
              return 0;
          }
          Number streamId = Math.floor(((channelId - 4) / 5.0d) + 1);
          if (log.isTraceEnabled()) {
              log.trace("Stream id: {} requested for channel id: {}", streamId, channelId);
          }
          return streamId;
      }
docs: Return stream id for given channel id.
  
  @param channelId
  Channel id
  @return ID of stream that channel belongs to