Synchronized Playback in Rapid Acquisition of Multicast Sessions
Huawei Technologies Co., Ltd.
Huawei Technologies Co., Ltd.
When watching the same IPTV channel, different TV sets may not render the same picture and the associated audio at the same moment. The variation in end-to-end delay that resulted in such asynchronous playback between users is referred to as inter-user playback delay. Unicast based rapid acquisition of multicast RTP sessions (RAMS) as specified in [I-D.ietf-avt-rapid-acquisition-for-rtp] is an important technique in achieving fast channel switching in IPTV as well as other multicast applications. In addition, RAMS also significantly relaxes the requirement of relatively short random access point period in encoding of video streams in multicast applications, thus allowing significantly improved compression efficiency. However, on the other hand, the use of RAMS increases inter-user playback delay, which makes users receiving the same multicast session playback the same content asynchronously. This document specifies a mechanism to help reduce inter-user playback delay caused by the use of RAMS.