843635 - Firefox 19 is rendering Flash much slower than version 16

Status: RESOLVED INCOMPLETE

(Core Graveyard :: Plug-ins, defect)

Description

[macster_smart]

User Agent: Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0
Build ID: 20130215130331

Steps to reproduce:

I've noticed this BUG on this website called Chaturbate which is an adult webcam streaming site that uses Flash to display webcams. 
The surface of the screen area that renders the Flash stream/cam can be resized and I always resize the Flash stream/cam content to a bigger size, that's when this BUG kicks in.
The bigger you resize the Flash content the slower it renders.
This issue might not be so evident on a super fast computer but believe me if you have a less powerful CPU or old one like I have the drop in rendering speed is very obvious.
This issue is present in Firefox since version 17 and propagates through versions 18 and now version 19. 
I have installed all these versions 17, 18 and 19 just to see if this BUG has been fixed but then I had to uninstall them and switch back to version 16.0.2 which doesn't seem to have this problem and renders much faster the Flash content.
I also uninstalled and installed new version of Flash player but there's not a Flash player issue but a Firefox one, actually I'm using Flash version 10.3.183.48.


Actual results:

The hardware acceleration in Firefox is turned off by default since it doesn't work on my setup, and regarding Flash I see that on Youtube videos when Flash content runs in page it says on "Show video info" "software video rendering, software video decoding" and when I switch the video to Fullscreen it says "accelerated video rendering, software video decoding"

My setup is pretty old and not so powerful that's why I can notice any speed increases or decrease in performance like this one with Flash rendering: 
Win XP SP3, Athlon XP 2600+ single core, ATI Radeon 9600 Pro, and 1.25 GB RAM.
Firefox extensions that I'm using:
- Firegestures
- Grab and Drag
- Tab Mix Plus
- Adblock Edge


Expected results:

This should have been fixed since version 17.

Comment 1

[Matthias Versen [:Matti]]

Resizing the flash area is slow on my system but it doesn't seem to be much faster with Firefox10ESR

What exactly is slow ?
Scrolling on the page, the video stream is choppy or the chat area is slow ?

Comment 2

[macster_smart]

(In reply to Matthias Versen [:Matti] from comment #1)

The video stream that is displayed/rendered by Flash is slow, it's like 2x or 3x slower in Firefox versions 19, 18 and 17 compared to how fast it runs on Firefox version 16, it's very evident that something has been changed since Firefox version 17 that causes this problem to occur and it hasn't been fixed till now.
I guess this problem can occur on any site that uses Flash even Youtube when the Flash is resized to a bigger screen area.

Comment 3

[Loic]

We need a testcase (public if possible) to test and find a possible regression range.

Comment 4

[Matthias Versen [:Matti]]

Loic: see comment:0 it's http://chaturbate.com/ (adult content!)
It doesn't look slower on my faster system and I'm unable to due a regression range search.