ffmpeg fails to duplicate video frames

Jay-Dolans-MacBook-Pro:test jdolan$ ffmpeg -y -i foo.flv -codec:a copy -r 24 -vsync cfr foo_.flv
ffmpeg version 1.1.git-716dbc7 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jun  8 2013 15:27:14 with Apple clang version 3.1 (tags/Apple/clang-318.0.61) (based on LLVM 3.1svn)
  configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libfreetype --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-nonfree --enable-libfaac
  libavutil      52. 34.100 / 52. 34.100
  libavcodec     55. 12.102 / 55. 12.102
  libavformat    55.  8.102 / 55.  8.102
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 73.100 /  3. 73.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
[flv @ 0x7f971103d800] max_analyze_duration 5000000 reached at 5014000 microseconds
Input #0, flv, from 'foo.flv':
  Metadata:
    creationdate    : Fri Jun 14 10:54:28
  Duration: 00:00:07.66, start: 0.000000, bitrate: 64 kb/s
    Stream #0:0: Video: flv1, yuv420p, 320x240, 1k tbr, 1k tbn, 1k tbc
    Stream #0:1: Audio: nellymoser, 22050 Hz, mono, flt
Output #0, flv, to 'foo_.flv':
  Metadata:
    creationdate    : Fri Jun 14 10:54:28
    encoder         : Lavf55.8.102
    Stream #0:0: Video: flv1 (flv) ([2][0][0][0] / 0x0002), yuv420p, 320x240, q=2-31, 200 kb/s, 1k tbn, 24 tbc
    Stream #0:1: Audio: nellymoser ([6][0][0][0] / 0x0006), 22050 Hz, mono
Stream mapping:
  Stream #0:0 -> #0:0 (flv -> flv)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=4.1 Lsize=      56kB time=00:00:07.70 bitrate=  59.9kbits/s
video:12kB audio:41kB subtitle:0 global headers:0kB muxing overhead 5.503581%