[mpv] Update readme

mpv/README.md

@@ -13,3 +13,28 @@ mpv is set up to hopefully strike a balance between high quality playback, strea
 * default video is adjusted for playback during the day, in a normally lit room
 * simple context menu (opened with `menu` key on keyboard) to load files, subtitles, chapters, and more
 * newly defined keybindings, look in `input.conf` for their definitions
+* when a battery
+
+## vim-like navigation
+
+Scrolling through videos can be done with h and l (or H and L for larger steps),
+scrolling through a playlist is accomplished with J and K,
+and volume is controlled with j and k.
+
+a controls playback speed, s cycles subtitles, d controls audio delay, u controls subtitle delay,
+f remains fullscreen, p toggles pauses, i shows the playlist, o peeks at the timeline, F5 takes a screenshot.
+
+Additionally, pressing the menu button (between right ctrl and alt) will open a little context menu,
+from which you can load other files, subtitles, chapters, switch audio tracks and take screenshots.
+
+Most of this is (thanks to the hard work of the original script writers) easily customizable,
+mostly from `input.conf` directly.
+
+## battery saving
+
+When mpv ist started on a pc which it assumes to be running on battery power, it will automatically switch to a (slightly) lower quality mode,
+foregoing some of the upscaling niceties integrated into the default high quality mode for (somewhat) better battery preservation.
+
+This script uses the output of `/sys/class/power_supply/AC/online`, and thus depends on this file being readable to get its information.
+
+It degrades gracefully, and simply keeps running in higher quality if the file is not readable.