пытаюсь перекодировать видео:
avconv -y -i aa.flv aa.avi

получаю:

avconv version 0.8.3-6:0.8.3-7, Copyright (c) 2000-2012 the Libav developers
  built on Aug 25 2012 11:19:52 with gcc 4.7.1
[flv @ 0xac4300] Estimating duration from bitrate, this may be inaccurate
Input #0, flv, from 'aa.flv':
  Metadata:
    creator         : STB
    metadatacreator : Yet Another Metadata Injector for FLV - Version 1.8
    hasKeyframes    : true
    hasVideo        : true
    hasAudio        : true
    hasMetadata     : true
    canSeekToEnd    : true
    datasize        : 278258877
    videosize       : 238760506
    audiosize       : 38900127
    lasttimestamp   : 2363
    lastkeyframetimestamp: 2363
    lastkeyframelocation: 278270953
  Duration: 00:39:23.36, start: 0.055000, bitrate: 934 kb/s
    Stream #0.0: Video: h264 (High), yuv420p, 638x480 [PAR 320:319 DAR 4:3], 806 kb/s, 25 tbr, 1k tbn, 50 tbc
    Stream #0.1: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
[buffer @ 0xac8740] w:638 h:480 pixfmt:yuv420p
[mpeg4 @ 0xacc360] Invalid pixel aspect ratio 320/319, limit is 255/255
Output #0, avi, to 'aa.avi':
  Metadata:
    creator         : STB
    metadatacreator : Yet Another Metadata Injector for FLV - Version 1.8
    hasKeyframes    : true
    hasVideo        : true
    hasAudio        : true
    hasMetadata     : true
    canSeekToEnd    : true
    datasize        : 278258877
    videosize       : 238760506
    audiosize       : 38900127
    lasttimestamp   : 2363
    lastkeyframetimestamp: 2363
    lastkeyframelocation: 278270953
    Stream #0.0: Video: mpeg4, yuv420p, 638x480 [PAR 320:319 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 25 tbc
    Stream #0.1: Audio: [0][0][0][0] / 0x0000, 44100 Hz, stereo, s16, 200 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> mpeg4)
  Stream #0:1 -> #0:1 (mp3 -> libmp3lame)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

что означает "Invalid pixel aspect ratio 320/319, limit is 255/255" и как от него избавиться ?