[h323plus] lost rtp packets and using jitter for video session

Hi, On connection speed greater than 384 kbps I have many lost rtp packets. If I switch off decoding of incoming video packets, than number of lost packets decreases. That is why I would like to try use jitter on video stream. I changed call of OpalMediaFormat() constructor inside OpalVideoFormat constructor in such way that needsjitter member become TRUE. But It is not working, not decoding any data. How can I use Jitter for my purpose and in general - can I do it? Igor Pavlov