code: public OggPacket getNextPacketWithSid(int sid) throws IOException {
          OggPacket p = null;
          while( (p = getNextPacket()) != null ) {
              if(p.getSid() == sid) {
                  return p;
              }
          }
          return null;
      }
docs: Returns the next packet with the given SID (Stream ID), or
  null if no more packets remain.
  Any packets from other streams will be silently discarded.