YouTube (News – Alert) has an enormous audience. This much should be abundantly clear from the sheer amount of videos that are uploaded to the site every day. Firefox also has a pretty large user base, so when you combine the two, that particular Venn diagram has quite a bit of overlap. But Firefox users may have noticed a little bit of a loss in functionality in recent days, especially for those turning to HTML5 as the presentation method of choice for those videos.

Those with an HTML5 capable browser—like Firefox—can get in on the HTML5 trial on YouTube, which will allow users to put the HTML5 capabilities to work. This in turn means no more needing to use Adobe (News – Alert) Flash to play videos, which will likely prove a welcome development. Those going out to YouTube’s page that allows for signups to take place, however, may notice a somewhat less welcome development, in that Google (News – Alert) has recently added some information to the page. Now, those signing up can see just what the particular browser being used supports, from HTMLVideoElement and H.264 to Media Source Extensions (MSE) and MSE & WebM VP9.

But for many older browsers—as well as Firefox and Safari—users will find that support for MSE, MSE & H.264, and MSE and WebM VP9 generally isn’t there. While HTML5 is offering up a bright future in terms of video online, allowing for media streams that play in JavaScript, it’s just not available on many browsers yet. But when it is, then a host of new services become available, like the MPEG-DASH adaptive streaming capability, or even complete live streams. Even encrypted video becomes a possibility, which itself has some interesting implications.

But for those who have signed up, these new options that will be forthcoming have also removed a few options today. Trying to select between resolutions—particularly stepping up to full 1080p or down to 480p—isn’t available any more for some users in HTML5, but interestingly, this problem goes away if users simply leave the HTML5 beta and start playing videos with Adobe Flash again.

The issue came when Google made the switch to MSE in adaptive streaming for both the 480p and the 1080p videos. Firefox doesn’t yet support MSE, so being able to switch to streams that actually use MSE is, for now, impossible. At last report, however, Mozilla (News – Alert) was working on bringing MSE to browsers, though it’s not clear just now when MSE will actually be on hand and full functionality restored.

Admittedly, this is a rather minor problem. Playing videos in 720p isn’t exactly a hardship, though if a video is available in 1080p it is a pretty pronounced step down. But even here, those involved can simply make the switch back to Adobe Flash and find full functionality restored until Mozilla gets together a version of MSE in Firefox.

Still, it’s kind of a kick in the teeth for users, especially those who went in with HTML5 as part of the trials to help improve HTML5 functionality on YouTube. But when it’s ready to go, there should be benefits aplenty, and we’ll all owe a small debt of gratitude to those who were there in the beginning, taking lumps like these so that future functionality could be improved.