We consider a wide-area video conferencing application where the video sources can adapt their send rates according to the available bandwidth in the network paths. We advocate a joint rate control of the sources to relieve the congestion, instead of running multiple instances of a single-source adaptation algorithm and additively superposing their results. The existing techniques work nicely with single-source trees, but do not work optimally in the case of multi-source trees with shared QoS goals. Using the well-known AIMD-based adaptation procedures, we incorporate the topology inferencing mechanism into a coordinated rate adaptation algorithm executed by the loss-experiencing sources. The paper provides a simulation based evaluation of our algorithm to corroborate the benefits.