Some but not all videos playback is terrible. This is the profile from "rocky (remi gaillard)". I've never seen ffmpeg that high in cpu percentage, unfortunately no package with symbols in debian.

samples  %        app name                 symbol name
831622   24.0674  no-vmlinux               (no symbols)
461558   13.3576  libavcodec.so.51.54.0    (no symbols)
196920    5.6989  libglib-2.0.so.0.1600.3  (no symbols)
181499    5.2526  libc-2.7.so              memcpy
159109    4.6047  libgobject-2.0.so.0.1600.3 (no symbols)
155720    4.5066  liboil-0.3.so.0.2.0      (no symbols)
122696    3.5509  libswfdec-0.7.so.0.0.0   upsample
119878    3.4693  libpixman-1.so.0.10.0    fbFetchTransformed
115230    3.3348  libpixman-1.so.0.10.0    pixman_blt_mmx
93905     2.7176  libswfdec-0.7.so.0.0.0   swfdec_video_decoder_decode
81140     2.3482  libpixman-1.so.0.10.0    fbFetchFromOneRectangle
72127     2.0874  libpixman-1.so.0.10.0    pixman_fill_mmx
56329     1.6302  libgstflump3dec.so       (no symbols)
46423     1.3435  libasound.so.2.0.0       (no symbols)
42719     1.2363  libswfdec-0.7.so.0.0.0   __i686.get_pc_thunk.bx