The green band likely means that the player isn't filling the space that Firefox reserves for it. Firefox creates a green window and overlays that green area with the actual player, so if you still see green then this means that something goes wrong and there is a difference between the player dimensions and the what Firefox thinks.

Are you using a High DPI display?

What is the current setting of layout.css.devPixelsPerPx on the about:config page?

Try to set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. You can adjust its value in 0.1 or 0.05 steps (1.1 or 0.9). Make sure you do not go too small or to high.

I am not certain what you mean with a high dpi display. I use a HP laptop 17 ak0xx with a 1600x900 resolution display.

The vertical green band is positioned somewhat to the left of the middle of the video, and over it. So I don't think it is the kind of problem you propose. I will try to attach a snapshot.

layout.css.devPixelsPerPx = -1 (default)

thanks!

Try set media.windows-media-foundation.allow-d3d11-dxva = false and restart the browser.

Looks like https://bugzilla.mozilla.org/show_bug.cgi?id=1352016 or https://bugzilla.mozilla.org/show_bug.cgi?id=1409105 (both should be fixed).

I don't have the variable media.windows-media-foundation.allow-d3d11-dxva in my config file.

There is only: media.webvtt........ and then media.wmf......... no media.wi.......

Can I add a new variable? How?

It could be media.wmf.dxva.d3d11.enabled or something like that. They change the name all the time.

Thanks!

I changed media.wmf.dxva.d3d11.enabled to false and the green band disappeared. Very greatful.