Source-Timed SDN Video Switching of Packetized Video

摘要

The broadcast industry is considering a move from serial digital interface (SDI) infrastructure to a computer-networked infrastructure. Professional media networking will enhance flexibility and agility of the broadcast plant, reduce and simplify cabling, provide for format-agnostic transport, and allow media organizations to benefit from the economies of scale of commercial off-the-shelf (COTS) networking hardware. One key element of video processing is synchronous ("clean") switching between video sources. The accuracy of the switch point recommended by SMPTE Recommended Practice (RP) 168 is on the order of 10 μs. Unfortunately, the current speed of networking switch flow rule changes using software-defined networking (SDN) is on the order of 1 to 10 ms, and the speed of rule changes is not highly deterministic. To solve this problem, source-timed video switching separates the actions of updating SDN flow rules from the timing of the actual video switch. This technique first adds new SDN flow rules to the networking switch that match a packet header value that is not currently being transmitted. Then, the video source changes its output's packet header value to the new value in the flow rule at the precise RP 168 video switch point. The new packet header value matches the new flow rules; thus, the effect of these two steps achieves precisely timed synchronous video switching (which can be compared with the actions of "preview" and "take" on a video switcher). Fox has developed a proof-of-concept of source-timed video switching using live high-definition SDI sources packetized using SMPTE 2022-6 and synchronously switched on a COTS 10 Gbit/sec Ethernet switch.