alt Hacker News> YouTube automatically edits the volume of videos that have an average loudness beyond a certain threshold.
For anyone else who was confused by this, it seems to be a client-side audio compressor feature (not a server-side adjustment) labeled as "Stable Volume". On the web, it's toggleable via the player settings menu.
https://support.google.com/youtube/answer/14106294
I can't find exactly when it appeared but the earliest capture of the help article was from May 2024, so it is a relatively recent feature: https://web.archive.org/web/20240523021242/https://support.g...
I didn't realize this was a thing until just now, but I'm glad they added it because (now that I think about it) it's been awhile since I felt the need to adjust my system volume when a video was too quiet even at 100% player volume. It's a nice little enhancement.
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The client side toggle might be new since 2024 but the volume normalisation has been a thing for a long time.
Youtube has been long normalizing videos standard feed, switching to a -14 LUFS target in 2019. But LUFS is a global target, and is meant to allow higher peaks and troughs over the whole video, and the normalization does happen on a global level - if you exceed it by 3dB, then the whole video gets it's volume lowered by 3dB, no matter if the part is quiet or not.
The stable volume thing is meant to essentially level out all of the peaks and troughs, and IIRC it's actually computed server-side, I think yt-dlp can download stable volume streams if asked to.