I often watch multiple videos simultaneously (don't ask why). Today I was trying to watch video1 and video2. The problem is not the overall volume, but rather the volume difference. If I raise the master volume then the second video is too loud, despite being on the lowest setting.
The question 'How to increase the volume on certain YouTube videos' is not relevant because the answers refer to increasing the overall volume of the computer rather than changing the volume of the video itself.
I use this bookmarklet for that:
javascript:(()=>{if(!!window.__volumeForced)return;window.__volumeForced=true;let forceVolume=()=>{document.getElementsByTagName('video')[0].volume=1;requestAnimationFrame(forceVolume);};forceVolume();})();
I'll explain, YouTube adjusts the maximum video volume so it is normalized. I tried checking the video's volume with the inspector, and in fact it was not 1.0 but ranging from 0.4 to 0.7 on some videos.
So what the bookmarklet does is, it finds the video element and sets its volume to 1.0 every frame using requestAnimationFrame.
And yes, because YouTube videos are loaded with AJAX, the code persists.
An addendum: I noticed that the volume resets sometimes when the window is not focused, possibly because of Chrome's limitations on background-running code
If you have VLC player installed, you can copy the video's URL and paste it onto VLC, it will fetch and play the video. VLC supports audio boosting up to 200% right on the volume control.
Also works with other sites, such as Twitch.tv and LiveLeak, but I don't know the full list.
