ffmpeg -i take1_sync.avi -vcodec copy -acodec copy -vf "scale=iw*sar:ih,setsar=1:1,scale=1280:720" -y take1_sync_sar.avi
ffmpeg version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  built on Jun 12 2012 16:52:09 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
Input #0, avi, from 'take1_sync.avi':
  Metadata:
    encoder         : Lavf53.32.100
  Duration: 00:23:23.95, start: 0.000000, bitrate: 27349 kb/s
    Stream #0.0: Video: mpeg4 (Simple Profile), yuv420p, 960x720 [PAR 4:3 DAR 16:9], 50 tbr, 50 tbn, 50 tbc
    Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s
Output #0, avi, to 'take1_sync_sar.avi':
  Metadata:
    ISFT            : Lavf53.21.0
    Stream #0.0: Video: mpeg4, yuv420p, 960x720 [PAR 4:3 DAR 16:9], q=2-31, 50 tbn, 50 tbc
    Stream #0.1: Audio: libmp3lame, 48000 Hz, stereo, 128 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
Press ctrl-c to stop encoding
frame=70191 fps=720 q=-1.0 Lsize= 4687216kB time=1403.82 bitrate=27352.3kbits/s
video:4629897kB audio:54831kB global headers:0kB muxing overhead 0.053127%