Unable to play any YouTube videos as "video formats not recognised"

Because H264 problem Do this
Test first If h264 can play or not
https://www.quirksmode.org/html5/tests/video.html
or test this
https://www.youtube.com/html5

if not then do this
https://msfn.org/board/topic/175591-ena ... hout-flash

about :config ->
media.gmp-eme-adobe.enabled (boolean; true)
media.gmp-eme-adobe.forceSupported (boolean; true; 49.0+)
media.gmp-eme-adobe.visible (boolean; true; 49.0+)
media.gmp-eme-adobe.version (string, not integer; 17)
media.gmp-eme-adobe.abi (string; x86-msvc-x86) (EDIT: x86-msvc-x64 for 64-bit XP users)
media.gmp.decoder.enabled (boolean; true)
media.eme.enabled (boolean; true)

about :support -> open folder ->
C:\Documents and Settings\kkman\Application Data\Mozilla\Firefox\Profiles\rf368dqm.default

make dir to
C:\Documents and Settings\kkman\Application Data\Mozilla\Firefox\Profiles\rf368dqm.default\gmp-eme-adobe\17

download
https://sdfox7.com/xp/sp3/EOL/primetime ... _40673.zip
extract zip and copy those files under \17
eme-adobe.dll
eme-adobe.info
eme-adobe.voucher

by Jesse Stone
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我遇到這問題快兩年了 一直無法解 下載很多plugin都無效 就用這個方法成功