The MediaSystemTest benchmark reports significantly lower than expected decoded/rendered frame rates when playing video encoded at 25,30,60 fps.
CPU load remains well below 100% to become a factor.

BigBunny_vp6_1280x720_3290_128_25p.flv

        CPU_USAGE 7046.875000 ms
        JFX_FPS 22.531956 fps
        JFX_MEDIA_DECDFPS 22.531934 fps
        JFX_MEDIA_DECODED 676.000000 frames
        JFX_MEDIA_RENDERED 676.000000 frames
        JFX_MEDIA_RNDRFPS 22.531934 fps
        JFX_PULSES 42.930695 pulses/sec
        MAX_MEMORY_USAGE 44508.000000 Kb
        REAL_TIME 30001.834032 ms

Note 22.53 < 25 fps.

BigBunny_vp6_1280x720_3710_128_30p.flv

        CPU_USAGE 7796.875000 ms
        JFX_FPS 26.866173 fps
        JFX_MEDIA_DECDFPS 26.866143 fps
        JFX_MEDIA_DECODED 806.000000 frames
        JFX_MEDIA_RENDERED 806.000000 frames
        JFX_MEDIA_RNDRFPS 26.866143 fps
        JFX_PULSES 48.565758 pulses/sec
        MAX_MEMORY_USAGE 44528.000000 Kb
        REAL_TIME 30000.553143 ms

Note 26.87 < 30 fps

BigBunny_vp6_1280x720_5843kb_128kb_60p

        CPU_USAGE 12031.250000 ms
        JFX_FPS 35.097923 fps
        JFX_MEDIA_DECDFPS 35.097884 fps
        JFX_MEDIA_DECODED 1053.000000 frames
        JFX_MEDIA_RENDERED 1053.000000 frames
        JFX_MEDIA_RNDRFPS 35.097884 fps
        JFX_PULSES 54.196770 pulses/sec
        MAX_MEMORY_USAGE 45308.000000 Kb
        REAL_TIME 30001.778997 ms

Note 35.1 < 60 fps