Are you facing the same issue with normal videos like in youtube?

When I'm watching youtube videos I don't have issues, although the quality is often low when playing the video, I can change to HQ and the video plays smoothly.

Can you give a link to a page or two that show this problem? I'm not sure how you put a video in the background and need to see an example. Thanks.

whiteboard.is uberconfernce.com

In these sites the background videos are pixelated, but if I browse with chrome or safari they are displayed in high quality, and I don't want to use those browsers ;)

Thank you for those. This is very interesting.

Here is what I get on Windows 7, I don't know how these things look on Mac:

(1) On http://whiteboard.is/ the site is serving OGV video, which is specified as an alternative to the MPEG-format video. It looks terrible, blotchy and jerky. The site's script (in the BigVideo.show() function) is not even testing whether Firefox supports MP4 and just goes straight to OGV.

To see how Whiteboard would look playing MP4, you can switch the video source using the Web Console. Select and copy the following line of script:

var v=document.getElementById("big-video-vid_html5_api"); v.setAttribute("src", v.getAttribute("src").replace(".ogv", ".mp4"));

Then, on Whiteboard, open the Web Console (Mac: Command+Alt+k, Windows: Ctrl+Shift+k), paste next to the caret (»), and press Enter to run it.

I can't think of an end-user solution for this.

(2) On https://www.uberconference.com/ on the other hand, I'm getting smooth playback of an MP4 video behind the gray overlay.

I can't see the vieo running on https://www.uberconference.com/, maybe it's related with some security configuration? If I go to http://www.businessmodelgeneration.com/training I can see the video running smoothly.

That new site actually is using Flash to play the video.

I have to apologize for forgetting that Firefox on Mac cannot yet play MP4s in its native HTML5 video player. The "bug" for adding support is linked in this thread: when will the web audio api support mp3 and m4a audio files? Websites that do not check for MP4 support and provide alternatives will definitely not work correctly on Firefox/Mac.