Tihs javascript snippet, when used as a bookmarklet, will attempt to speed up playback of all media elements (video, audio) by changing the playbackRate property to 1.8. This rate can easily be modified to suit your preference (if you've already "installed" the bookmarklet, right click it and select edit; look for the 1.8 and change it). The easiest way to "install" it is to drag the link below to your browser's bookmarks bar.
Actually, this won't work here from a gist. Have to setup GH page. In the meantime, copy the code from the code block below, bookmark this page, then edit the bookmark and paste in the code you copied to replace the destination URL.
[Video++](javascript:void function(){try{document.querySelectorAll("video, audio").forEach(e => e.playbackRate=1.8);console.log("media playbackRate modified, hopefully")}catch(a){console.error("Error changing playbackRate. Is there media on this page%3F","("+a+")")}}();)
javascript:void function () {
try {
document.querySelectorAll("video, audio").forEach(e => e.playbackRate = 1.8);
console.log("media playbackRate modified, hopefully")
} catch (a) {
console.error("Error changing playbackRate. Is there media on this page%3F", "(" + a + ")")
}
}();