avconv error

 avconv -i ku2sRHh170fMwb5  -vcodec libx264 -threads 0 -r 25 -g 25 -b 500k -bt 500k -acodec libvo_aacenc -ar 44100 -ab 64k -y out.mp4
avconv version 10_alpha1, Copyright (c) 2000-2013 the Libav developers
  built on Feb  3 2013 13:48:07 with gcc 4.4.5 (Debian 4.4.5-8)
Input #0, avi, from 'ku2sRHh170fMwb5':
  Metadata:
    encoder         : VirtualDubMod 1.5.10.3 | www.virtualdub-fr.org || (build 2550/release)
  Duration: 01:29:27.16, start: 0.000000, bitrate: 2201 kb/s
    Stream #0.0: Video: mpeg4 (Advanced Simple Profile), yuv420p, 720x400 [PAR 1:1 DAR 9:5], 23.98 tbn, 23.98 tbc
    Stream #0.1: Audio: ac3, 48000 Hz, 5.1, fltp, 384 kb/s
[libx264 @ 0x1ba8200] using SAR=1/1
[libx264 @ 0x1ba8200] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle Cache64
[libx264 @ 0x1ba8200] profile High, level 3.0
[libx264 @ 0x1ba8200] 264 - core 120 r2151 a3f4407 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=3 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=25 keyint_min=2 scenecut=40 intra_refresh=0 rc_lookahead=25 rc=abr mbtree=1 bitrate=500 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.25 aq=1:1.00
[libvo_aacenc @ 0x1ba5b60] Unable to set encoding parameters
Output #0, mp4, to 'out.mp4':
  Metadata:
    encoder         : VirtualDubMod 1.5.10.3 | www.virtualdub-fr.org || (build 2550/release)
    Stream #0.0: Video: libx264, yuv420p, 720x400 [PAR 1:1 DAR 9:5], q=-1--1, 500 kb/s, 90k tbn, 25 tbc
    Stream #0.1: Audio: libfaac, 44100 Hz, 5.1, s16, 64 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg4 -> libx264)
  Stream #0:1 -> #0:1 (ac3 -> libvo_aacenc)
Error while opening encoder for output stream #0:1 - maybe incorrect parameters such as bit_rate, rate, width or height