Multimedia services are already part of our days, providing delivery of pictures, video or voice to the users. The streaming provider allows the users to start displaying the data before the entire stream has been transmitted. The communication between the clients and the server could evolve in various ways, according to the packet forwarding, it could be unicast, broadcast, multicast. In computer networking, IP multicast is widely used in Internet Protocol applications of streaming media and Internet television where the same term need to be transfered. The aim of the multicast addressing is that by choosing the destination address of a multicast group, the data can be delivered to the joined clients simultaneously with a single transmission. If the topology of the network requires, the routers may create copies of data packets automatically, thus saving significant bandwidth. The joined users of the group have different network connection, which could highly influence the quality of the multimedia service. If the bitrate of the sent video is much more higher, than the receiver’s connection bandwidth the packets could be lost and, the quality of the video could decline. My task is to work out new methods, to decrease the quality disruption due to the different connections. In order to increase the efficiency I worked out algorithms, using them on server side to choose the propriate video bitrate. In the first section of my thesis I give an overview about the multimedia services, summarizing the characteristics of the multicast data forwarding technics. After the introduction I examine the multicast streaming traffic between the clients and the server on a real test network, and introduce the prepared adaptive multicast video choosing algorithms. In order to increase the multicast application efficiency, in my presented solution the server maps the quality (delay, bandwidth) of the connection with the clients and chooses the appropriate video’s bitrate. In the last section I analyze the results and summarize my experiences.