На https://bugzilla.mozilla.org/show_bug.cgi?id=806917 обсуждают поддержку 1.0, а у нас вообще никакого нет. В about:config ни слова о gstreamer.
xulrunner-24.0-alt1 -> sisyphus: * Thu Sep 26 2013 Alexey Gladkov <legion@altlinux> 24.0-alt1 - New release (24.0). - Add gstreamer support (ALT#29454). - Fixed: + MFSA 2013-92 GC hazard with default compartments and frame chain restoration + MFSA 2013-91 User-defined properties on DOM proxies get the wrong "this" object + MFSA 2013-90 Memory corruption involving scrolling + MFSA 2013-89 Buffer overflow with multi-column, lists, and floats + MFSA 2013-88 compartment mismatch re-attaching XBL-backed nodes + MFSA 2013-87 Shared object library loading from writable location + MFSA 2013-86 WebGL Information disclosure through OS X NVIDIA graphic drivers + MFSA 2013-85 Uninitialized data in IonMonkey + MFSA 2013-84 Same-origin bypass through symbolic links + MFSA 2013-83 Mozilla Updater does not lock MAR file after signature verification + MFSA 2013-82 Calling scope for new Javascript objects can lead to memory corruption + MFSA 2013-81 Use-after-free with select element + MFSA 2013-80 NativeKey continues handling key messages after widget is destroyed + MFSA 2013-79 Use-after-free in Animation Manager during stylesheet cloning + MFSA 2013-78 Integer overflow in ANGLE library + MFSA 2013-77 Improper state in HTML5 Tree Builder with templates + MFSA 2013-76 Miscellaneous memory safety hazards (rv:24.0 / rv:17.0.9)
Спасибо!