Simple install ffmpeg from medibuntu and install libavcodec-extra-52.
Save your original file and link to the system ffmpeg binary with ln -s so you don't have to update any code within dolphin.
(cd flash/modules/global/app ; mv ffmpeg.exe ffmpeg.exe.orig ; ln -s /usr/bin/ffmpeg ffmpeg.exe )
You can also add '-threads 2' argument to it's command line, and boost even more.
(flash/modules/video/inc/header.inc.php + flash/modules/video_comments/inc/header.inc.php)
If you can't do above you need to change $GLOBALS['sFfmpegPath'] in the above files.
From 8 frames/s on a Phenom II X6 processor to 51 frames/s with -threads 3 ;)
Now I need to figure out if vaapi is possible on newer onboard graphics card (HD4xxx) to
improve video encoding, who don't want their own video hardware accelerator in their server ;)