Half-Life is a famous first-person shooter released in 1998. These days Half-Life has a vibrant speedrunning community where players try their best to complete the game as fast as humanly possible. Single-sitting speedruns, when people play through the game from start to finish, are usually streamed and recorded live. But segmented or tool-assisted speedruns—big projects that take weeks or months to complete—use demo files, which capture player actions and can be played back in-game. The demos are recorded to videos post-factum, typically at high resolution and quality. This video recording of demos can be done faster than real-time, which can save multiple real-life hours.

In this post I’ll show how I implemented a tool capable of recording 1920×1080@60 Half-Life footage at up to 3 times faster than real-time on a reasonably powerful PC.¹ The tool uses the Vulkan graphics API to capture the game’s frames and convert their color space before encoding.