Abstract: Embodiments of the invention enable the synchronization of clocks across packet switched networks, such as the Internet, sufficient to drive a jitter buffer and other quality-of-service related buffering. Packet time stamps referenced to a local clock create a phase offset signal. A shortest-delay offset generator uses a moving-window filter to select the samples of the phase offset signal having the shortest network propagation delay within the window. This shortest network propagation delay filter minimizes the effect of network jitter under the assumption that queuing delays account for most of the network jitter. The addition of this filtered phase offset signal to a free-running local clock creates a time reference that is synchronized to the remote clock at the source thus allowing for the transport of audio, video, and other time-sensitive real-time signals with minimal latency.

Abstract: A forward error correction (FEC) encoding system and method optimized for protecting real-time audio-video streams for transmission over packet-switched networks with minimal latency. Embodiments of this invention provide bandwidth-efficient and low-latency FEC for both variable and constant bit-rate MPEG-encoded audio and video streams. To maximize bandwidth-efficiency and playable frame rate for recovered media streams, embodiments of the invention may sort packets by content type and aggregate them into FEC blocks weighted by sensitivity in the recovered stream to packet loss of a particular content type. Embodiments of this invention may use temporal constraints to limit FEC block size and thereby facilitate their use in the transport of VBR streams.

Abstract: An Automatic Repeat request (ARQ) error correction method optimized for protecting real-time audio-video streams for transmission over packet-switched networks. Embodiments of this invention provide bandwidth-efficient and low-latency ARQ for both variable and constant bit-rate audio and video streams. Embodiments of this invention use timing constraints to limit ARQ latency and thereby facilitate the use of ARQ packet recovery for the transport of both constant bit rate and variable bit rate media streams.