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.

Abstract: A system and method for virtual link aggregation for combining network links of various types and speeds to increase throughput and reliability for packetized transport. In contrast with physical port trunking, the system does not require direct control over ports or network interfaces. Instead, the system rewrites packet addresses and works through existing networking equipment, without requiring any new or special protocols, processing, or equipment within the network. The system works through low-level rerouting by rewriting hardware addresses and/or high-level routing by rewriting logical addresses. Thus packets are redirected through multiple routes to a common destination via alternate gateways and links. Different algorithms may be employed to balance the load on each link and determine an optimal route for each packet. Embodiments may also employ packet flow or stream identification and thereby only provide link aggregation for a specified set of packet flows.

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: 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: Embodiments of the invention enable minimum latency site independent real-time video transport over packet switched networks. Some examples of real-time video transport are video conferencing and real-time or live video streaming. In one embodiment of the invention, a network node transmits live or real-tine audio and video signals, encapsulated as Internet Protocol (IP) data packets, to one or more nodes on the Internet or other IP network. One embodiment of the invention enables a user to move to different nodes or move nodes to different locations thereby providing site independence. Site independence is achieved by measuring and accounting for the jitter and delay between a transmitter and receiver based on the particular path between the transmitter and receiver independent of site location. The transmitter inserts timestamps and sequence numbers into packets and then transmits them. A receiver uses these timestamps to recover the transmitter's clock.