Automatically mutes the Twitch player when an advertisement started and unmute it once finished. You can also hide ads by setting the property disableDisplay to true. There's several variables you can edit as you want.

2020-11-01 Notice: uBlock Origin once in a while doesn't work properly to block the ads. Temporary fix likes this one makes things worse. I decided to quickly update my script and use it again in the meantime. Previously noted problem below doesn't seem to be existing anymore.
2019-11-24 Notice: Use uBlock Origin. Twitch wants you to see their ads too much. They hindered this script again by delaying the display of the ad notice (used to know if an ad is in progress), and by pausing the ad despite the player is in a playing state.

Changelog :

• v1.15: Cleaned up the code a bit, as the period with co-existing players is long gone. Also copied the volume currently set over the small stream player displayed top right during ads.
• v1.146: Enabled stream audio during ads, when Twitch allow you to see the stream top right (and you don't have it muted before the ad(s)).
• v1.145: Updated with the new changes with ads on Twitch (others updates may follow, seems to be some massive changes, with new "audio ads" and such). Also minor fix for squad streams. Switching to squad stream mode previously during an ad would not keep the ad detection.
• Since v1.1441, added yet another potential fallback in case of a new class name change. So that old versions of the script may still work.
• v1.14: Updated with latest Twitch changes. They keep obfuscating class names.
• v1.13: Updated due to current offensive of Twitch towards adblockers. It's unbearable. Note: Squad might not work atm, i don't know if they did class changes since. Will update if needed.
• v1.11 & 1.12: Highwind or old player is automatically detected.
• v1.10: Updated for the new "Highwind player".
• v1.09: Updated the display of Ads Options buttons in the new Twitch design.
• v1.08: Added Squad page support.
• v1.07: Added a minimum ads duration since Twitch sometimes removed the ad notice before the end. Default to 15s, editable.
• Since v1.06, it displays an "Ads Options" button next to the viewer count to allow you to switch temporarily from your default display setting for the player during an ad (show/hide), or to unlock the player in case the ad notice wasn't properly removed at the end of the ad(s) by Twitch and you don't want to wait the auto unlock (set to be triggered after 2m30 elapsed with ad(s) in progress).