WMODE and Flash Video - stability and performance

Question

for a business reasons I need to overly Flash video player with HTML content. This requires the WMODE to be set as "opaque".

However Flash Player Engineering Tinic Uro warns us over lower performance and couple years ago he even mentioned serious instability and Adobe TechNote 15523 states "the WMODE parameter is supported only on some browser/Flash Player version combinations".

In addition there is whole bunch of bugs associated directly with the WMODE option (search for "wmode" and "opaque" in Adobe Flash Player Bug and Issue Management System)

To my knowledge even YouTube tries to avoid using the WMODE "opaque" at any cost, just have a look at the design of the account drop down menu above expanded video.

My question is:

Do you have any experience with lower performance, bugs or instability regarding Flash video and WMODE "opaque"? Can you share any good reading on this topic?

Lengel

Answer 1

Yes, wmode opaque can hinder performance. "transparent" is even worse. However,

1) It's not as bad as it was a while ago (when sometimes it wouldn't work at all).

2) Most importantly, performance hit is only on certain situations. I have ran into two different situations: a) you have a part of your SWF that is being redraw, and that part of the SWF (dirty rectangle) is close to some HTML content. This forces the browser to redraw the HTML content every time the SWF part is redrawn, thus losing performance; and b) user events like a mouse rolling over a button that is close to HTML content can also be a problem... the browser seems to lose a few frames every time you move the mouse (to determine what's below the cursor, maybe?) so if you have a quick rollover (say, something that takes 0.3s) it's very easy to notice the animation 'lagging' as you move the mouse and it loses some frames.

Point is, if you can avoid situations where you are interacting with animated content below the HTML area, or if you can disable the HTML content sometimes, using opaque is ok.

Performance also vary between browsers, so be sure to test well.

Arlaarlan

great answer, one more question: how did you test the performance? Just visually or in Taskbar? Is there any proper way of measuring? – Lengel

There are ways of testing it by measuring the number of rendered frames per second and seeing how it compares to the target framerate, but my tests were done mostly just by moving the mouse and perceiving animation speed. SWF rendering would halt for a quarter of a second or so when doing that, and not do so when wmode was set to the default, so it was easy to just get to the conclusion that wmode=opaque was causing the performance impact. I also had github.com/zeh/as3/blob/master/com/zehfernando/display/debug/… to measure performance graphically. – Arlaarlan

Answer 2

I personally don't have any issue with it. But most sites seem to hide the flash content when something such as a modal dialog is being displayed on top of the flash content and made visible again once it's closed.

I would like to add:

After changing the WMODE to opacity, the input boxes could not have special characters (icelandic, such as þ, ð) in them. I'm unsure if this is an issue for everyone.

Bedivere

I think that special chars issue is a known issue -- I've seen it mentioned somewhere. FireFox only, right? – Arlaarlan