ffmpeg -i la-villa-strangiato-acoustic-intro.mp4 -r 8 -vf "setpts=(4/1)*PTS" la-villa-strangiato-acoustic-intro-quarter-speed.mp4
FFmpeg version 0.6.5, Copyright (c) 2000-2010 the FFmpeg developers
  built on Jan 29 2012 17:52:15 with gcc 4.4.5 20110214 (Red Hat 4.4.5-6)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --incdir=/usr/include --disable-avisynth --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC' --enable-avfilter --enable-avfilter-lavf --enable-libdc1394 --enable-libdirac --enable-libfaac --enable-libfaad --enable-libfaadbin --enable-libgsm --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libx264 --enable-gpl --enable-nonfree --enable-postproc --enable-pthreads --enable-shared --enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
  libavutil     50.15. 1 / 50.15. 1
  libavcodec    52.72. 2 / 52.72. 2
  libavformat   52.64. 2 / 52.64. 2
  libavdevice   52. 2. 0 / 52. 2. 0
  libavfilter    1.19. 0 /  1.19. 0
  libswscale     0.11. 0 /  0.11. 0
  libpostproc   51. 2. 0 / 51. 2. 0
[aac @ 0x12283e0]Transition from an ONLY_LONG or LONG_STOP to an EIGHT_SHORT sequence detected. If you heard an audible artifact, please submit the sample to the FFmpeg developers.

Seems stream 0 codec frame rate differs from container frame rate: 59.83 (29917/500) -> 29.92 (29917/1000)
    Last message repeated 1 times
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'la-villa-strangiato-acoustic-intro.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf52.64.2
  Duration: 00:00:06.96, start: 0.000000, bitrate: 595 kb/s
    Stream #0.0(und): Video: h264, yuv420p, 480x360 [PAR 1:1 DAR 4:3], 484 kb/s, 29.92 fps, 29.92 tbr, 29917 tbn, 59.83 tbc
    Stream #0.1(und): Audio: aac, 44100 Hz, stereo, s16, 106 kb/s
Unrecognized option 'vf'