Stop autoplay on YouTube but enable buffering

Question

There's already a question asking about how to stop YouTube videos from automatically playing. However, the solution there doesn't satisfy me as it prevents the video from buffering in the background.

Is there any way to prevent YouTube from automatically starting the playback, while still allowing the video to be buffered? My browser of choice is Firefox so extensions would also be valid solutions.

I would be especially interested in any solution that will allow me to choose the quality in which the buffering will be performed—for example, a solution that will allow me to always set videos to the highest quality mode available up to and including 720p, while still starting them at "pause" mode.

Answer 1

I know you asked for Firefox explicitly, but if you were to move to Chrome you could use the Stop Autoplay for YouTube extension (which stops playback yet allows buffering) combined with the Auto HD for YouTube to automagically select your preferred quality levels.

Both plugins can be found on Google's Chrome Extensions.

EDIT:
For FireFox, you could install GreaseMonkey and use this script which does what you want (and supposedly blocks adverts as well): http://userscripts.org/scripts/show/49366

Answer 2

With Firefox you can use YouTube Control Center open source add-on to configure autoplay behavior, buffering and much more.

Answer 3

As of now (2015-10), I can't get any buffering on YouTube, which, according to Lifehacker ("Preload Entire YouTube Videos By Disabling Dash Playback"), is due to Dynamic Adaptive Streaming over HTTP, or DASH. Complaints about buffering are widespread but most seem outdated as there is at least some buffering happening, but these days there is none.

To extend on Diego V's answer, YouTube Center is the solution, and it is available in numerous browsers including Chrome, but it is tricky to get as it is not on the Chrome Web Store:

• Install Tampermonkey—it is on the Chrome Web Store.
• Check out the Userscript section of YouTube Center. I like OpenUserJs.org but there are a couple options. Click install to install one.
• When you go to YouTube, look for a gear icon in the top left corner. If you don't see it at first, try refreshing and navigating around until it shows up—I had to fiddle for a bit. You may have to restart the browser.
• For me, it automatically enabled buffering even without unchecking the DASH box in the Player Settings menu, but if it doesn't you should try it.
• I fond that some videos still didn't buffer.