YouTube TV is adding 4K support and offline playback, but it’s going to cost you. Google detailed YouTube TV’s “4K Plus” subscription add-on, which costs an extra $20 on top of the standard $65-per-month plan, for a total of $85 per month. 4K Plus might sound like it will simply provide a resolution bump, but subscribing to the higher tier will also unlock a new offline playback feature and unlimited simultaneous streaming over home Wi-Fi. The latter feature is otherwise limited to three streams per account. The one no-extra-cost feature of today’s announcement is 5.1 audio support, which is rolling