Tomas Bacik - CDN Challenges of HTTP-based Low Latency Live Streaming Delivery

The presentation goes through the CDN set-up workflow from the origin to the edge and discusses the tweaks and optimisations that need to be done to deliver HTTP low latency (~5s) live streaming without compromising quality.

From transcoding and storage all the way to caching and delivery, there are multiple points for optimization in a low-latency streaming stack.

This presentation delves into both edge-oriented features, such as custom-built, nginx-based request coalescing, and intuitive cache pre-warming, which allows us to pre-push stream chunks to edges across the globe with multiple quality profiles. These optimizations can drastically reduce initializion time, as well the number of requests hitting origin encoders in peak-heavy scenarios such as large sporting events, etc.

Moving towards the origin and encoding, it will explore the possibilities of methods, such as per-title encoding utilizing optimized bitrate ladders based on content-aware convex hull methods. This allows us to serve better-looking content over noticeably lower bitrates, something particularly useful when adapting LL-streaming to users with slower/mobile connection.

Throughout our development we have been evaluating and testing which approaches and methods offer substantial effect and which present what we call “diminishing results”. This presentation will introduce what we believe is the key combination of methods for low-latency http-based formats to stay relevant, even in the world of emerging WebRTC-based streaming.

This talk was presented at Demuxed '23, a conference for video nerds in San Francisco featuring amazing talks like this one.