Mattias Buelens - The curious player of Benjamin Button: reverse video on the web

The video element is the foundation of all video experiences on the web. Yet one key feature is still missing in most browsers: playing a video in reverse. The HTML specification defines how a negative playback rate should be handled, but only a single browser actually implemented this (thanks Safari!). This lack of support is a problem for advanced use cases, such as video editing or subtitle authoring.
In this talk, I will explore how to make a video play in reverse inside a web browser. Since a regular video element won’t do the trick, I’ll take control of decoding and rendering the individual frames using WebCodecs. I’ll dive deeper into some of the challenges that arise when playing in reverse, such as:
* How to keep playback smooth without stuttering.
* How to buffer enough GOPs, without stalling the hardware decoder.
* How to adapt a streaming video player’s download loop to support buffering in reverse.
This talk was presented at Demuxed '23, a conference for video nerds in San Francisco featuring amazing talks like this one.