It would clever for embedded videos to have their own script to pause when they go off screen and resume when they come back on screen. But if that existed, you would think it would behave consistently when you view the same embedded video on different pages and in different browsers.

Could you try Firefox's Safe Mode? That's a standard diagnostic tool to bypass interference by extensions (and some custom settings). More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

Any difference?

Whoops, after a closer reading, I see you already tested in Firefox's Safe Mode. I'll have to recover my Tumblr password and see whether I can replicate this.

lol I was about to say, I thought I had said it already. Oh well, it's early and we all make mistakes.

I also asked some Firefox-using friends, and apparently the same issue has been happening with them.

But anyways jscher2000, if you see the issue or not, let me know?

Could I replicate it by looking at someone else's page, or does it only occur when you are logged in and viewing your own pages? If I could view someone else's page, that would be really convenient.

I'm not sure if it would happen while logged out, but doing both logged out and logged in would probably be good, for experimentation's sake.

However the way I am experiencing it right now is logged in and looking in my Dashboard or the tags. If you go in your Likes, Drafts, or Queue, and try to replicate it there, it doesn't happen (or it hasn't with me). It also doesn't seem to happen if you're on someone else's page.

Just Dashboard, personal/main/whatever dashboard (the one with only your posts), and in tags on the Dashboard.

Also, I am asking around, and apparently other people are having the issue too.

Anything you can think of to make this easier to study would help. I don't know whether the volunteers here will be able to create a page that replicates the problem.

Hello jscher2000

Don't know why they would be unable to create a page- it's free to do so and people usually won't follow a blank blog.

Anyways, tried to replicate it, but due to the way Tumblr now formats its tags when a user is offline, checking it is a bit difficult, as it seems to only do picture posts, and even then only a certain amount.

In short, it looks like someone will have to test this out while logged in.

One more thing: Experimented a little- it doesn't matter if the video is paused or not. It also occurs if the video is playing as well.

Walk me through this, please. Assume I use Tumblr once a year (ahem).

I have icons for creating Audio and Video posts; I don't see one for Music posts. It's pretty obvious how to create a video post with a YouTube URL. Audio posts with a YouTube URL did not work for me. ??

Maybe it's easier if I follow you?

Hello jscher2000, sorry for the late reply, I was out. Yeah, I'll tell you what I was doing, so maybe you can follow in my footsteps. 1) I was looking through the tags on Tumblr, specifically this one, though I don't think it matters which: http://www.tumblr.com/tagged/blutengel 2) Clicked on a YouTube video (any one will do. Also, YouTube audio posts are made by actually going to the video on YT, clicking the Share button, and clicking the Tumblr icon). 3) Scrolled back down to look at other posts. 4) Scrolled back up...thus the video restarted. 5) Since I had already Liked the video (by clicking on the heart icon), I experimented by also placing it in my Queue and drafts- the problem did not occur there.

Anyways, that's that, if you want to try replicating.

Oh yeah, I might also mention that it doesn't happen when it's in my Likes either.

Thanks for the example.

I see: scrolling a certain distance away from the video somehow stops it (presumably a script does this), while scrolling a certain distance toward the video restarts it (annoyingly, from the beginning).

The video is set to autoplay. The reason it doesn't autoplay until after you click it is that it is hidden by a preview image. Clicking the preview image hides the image and displays the video. Stopping the video does not hide the video (or clear the autoplay). If it did, the video would not restart. However, that's not a trivial hack...

Well, after two hours poking around, I'm no closer to figuring out why behaves this way.

Hello, and thanks for your reply. It's not just that video though. For example, type in a popular band/musician/whatever that you like into the tag search at the upper right corner. 2) click on a Youtube video. 3) Repeat process that I detailed in my previous post. It's doing this for all the videos. I presume that you tried it as well, and got the same issue? I guess I'm also wanting someone else to try it, so I can see if it's one of those "just me" things.

Hey jscher2000 (and anyone else who reads and/or wants to chime in here), 1) Just uninstalled Firefox, which included getting rid of my profiles, customizations, and the like (in short, I'm starting afresh pretty much), and then re-downloaded it. Problem is still there. 2) Decided to check other sites that allow embedding, such as Facebook and Deviantart. Nope, no issue. Just Tumblr is where that issue seems to reside.

It's not just you. I got it with other Youtube videos on "tagged" searches as well.

Alright. And like I said above, I tried starting over from scratch, and the problem is still there.

Is there any way that you could try that too, just so I can make sure I did it correctly?

Sorry I'm asking so much. I'm just asking because I also e-mailed Tumblr support staff, and they have an annoying tendency to blame the user before the site itself. I just want to make sure I have my bases covered.

I'm convinced. I tested in a new profile, which is uncustomized except for having the full collection of plugins installed on the system and one extension associated with my security software. (For future reference: Profile Manager - Create, remove or switch Firefox profiles.)

As I scroll up and down, any videos that I've unhidden stop and restart regardless of whether I pause them. What's causing this is something in Tumblr's scripts that adds and removes display:none to posts as the user scrolls the page. This triggers Firefox to stop the playback and then to start it again.

Stopping and restarting Flash automatically when display is toggled may be unique to Firefox. Neither IE9 not Chrome 29 appears to do it on this test page: http://www.jeffersonscher.com/forumsh.../toggle_display.html. If there is a way to prevent Firefox from doing that, I'm not aware of it.

But you can use a Greasemonkey userscript (or if you prefer, a Stylish userstyle) to prevent the script from hiding videos, thus avoiding the problem. A test version is available here: http://userscripts.org/scripts/show/177648. It adds this to Tumblr pages to override the page script's addition of display:none to posts:

<style type="text/css">li.post_container > div.post_full.is_video {display:block !important;}</style>