Bad quality of shared image

[matclab]

When sharing from firefox with last jidesha extension, the image is very pixelated (and test is unreadable) — a bit alike what skype does when sharing screen on linux.

We tried with the same user on the same condition under chrome, and everything went smoothly (i.e, a bit pixelated, but getting better in one second on static images).

Any idea on what may cause the problem and how to solve it ?