Encoding, fast and slow: low-latency video processing using thousands of tiny threads

Abstract

We describe ExCamera, a system that can edit, transform, and encode a video, including 4K and VR material, with low latency. The system makes two major contributions. First, we designed a framework to run general-purpose parallel computations on a commercial cloud function service. The system starts up thousands of threads in seconds and manages inter-thread communication. Second, we implemented a video encoder intended for fine-grained parallelism, using a functional-programming style that allows computation to be split into thousands of tiny tasks without harming compression efficiency. Our design reflects a key insight: the work of video encoding can be divided into and parts, with the slow work done in parallel, and only fast work done serially.