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BBC Optimizing UHD Video Streaming Over IP (bbc.co.uk)
johnslater writes: A friend at the BBC has written a short description of his project to deliver UHD video over IP networks. The application bypasses the OS network stack, and constructs network packets directly in a buffer shared with the network hardware, achieving a ten-fold throughput improvement. He writes: "Using this technique, we can send or receive uncompressed UHD 2160p50 video (more than 8 Gbps) using a single CPU core, leaving all the rest of the server's cores free for video processing." This is part of a broader BBC project to develop an end-to-end IP-based studio system.
IP packets and Ethernet frames are really quite small data structures, so the cost of processing is vastly overshadowed by the cost of scheduling, context switching, memory management, etc.. Because modern CPUs are limited by RAM access latency, they're only fast when they can either loop or stream. If there isn't enough of that between the overhead, performance tanks.
Yeah, this kind of thing has been around for a while.
These days the added latency of going through the kernel IP stack is generally measured in micro rather than milliseconds but the difference is still the same order of magnitude. Solarflare, Mellanox and others will happily sell you expensive Ethernet network cards that come bundled with drivers that let you bypass the kernel IP stack. The stack itself isn't especially slow but the system call and extra memcpys still do all add up. I've also seen an in-house user space stack built largely on top of lwIP.
So I'd agree that none of this particularly new, but I reckon it's still interesting that the BBC is using it. Maybe that'll help spur more widespread adoption.
This isn't for you to watch UHD. It's for internal use in production, so they can shunt live UHD video around their studios. That way they keep full quality right up until the final stage before distribution, when it gets resized according to the end device. Your TV will get plain old 1080p as always - but they'll have UHD capability ready to go for transmitting to cinemas or sending to big public displays, and they can archive a UHD version for future use so they can zoom in tighter on the action in future highlights.