No hay audio después de la conversión de AVI a SWF usando ffmpeg

Pude convertir el video de AVI a SWF, sin embargo, el sonido parece haberse eliminado. Estoy ejecutando el siguiente comando

ffmpeg -i 1.avi -b:a 3000k -vcodec flv -ab 128k -ar 44100  -acodec libmp3lame -b:a 160k -ac 2 -ar 44100 output.swf

Intenté una conversión similar de MP4 a AVI y no tuve problemas.

Estoy ejecutando Windows XP 32bit

EDITAR

He incluido la salida de ffmpeg después de la conversión. La única diferencia es que estoy intentando convertir un archivo MP4 en lugar de un AVI pero los resultados son los mismos, es decir, un archivo SWF con video pero sin audio

ffmpeg version N-38632-g4cda8aa Copyright (c) 2000-2012 the FFmpeg developers
  built on Mar  8 2012 02:38:08 with gcc 4.5.0 20100414 (Fedora MinGW 4.5.0-1.fc
14)
  configuration: --prefix=/var/www/users/research/ffmpeg/snapshots/build --arch=
x86 --target-os=mingw32 --cross-prefix=i686-pc-mingw32- --cc='ccache i686-pc-min
gw32-gcc' --enable-w32threads --enable-memalign-hack --enable-runtime-cpudetect
--enable-cross-compile --enable-static --disable-shared --extra-libs='-lws2_32 -
lwinmm' --extra-cflags='--static -I/var/www/users/research/ffmpeg/snapshots/buil
d/include' --extra-ldflags='-static -L/var/www/users/research/ffmpeg/snapshots/b
uild/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-version3 --enable-n
onfree --enable-libx264 --enable-libspeex --enable-libtheora --enable-libvorbis
--enable-libfaac --enable-libxvid --enable-libopencore-amrnb --enable-libopencor
e-amrwb --enable-libmp3lame --enable-libvpx --disable-decoder=libvpx
  libavutil      51. 42.100 / 51. 42.100
  libavcodec     54. 10.100 / 54. 10.100
  libavformat    54.  2.100 / 54.  2.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 63.100 /  2. 63.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  7.100 /  0.  7.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.0.3
  Duration: 00:02:41.04, start: 0.000000, bitrate: 2378 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x720,
 2253 kb/s, 24 fps, 24 tbr, 24 tbn, 48 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 126
 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    :
[buffer @ 0x201de80] w:1280 h:720 pixfmt:yuv420p tb:1/1000000 sar:0/1 sws_param:

Output #0, swf, to '2.swf':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf54.2.100
    Stream #0:0(und): Video: flv1, yuv420p, 1280x720, q=2-31, 200 kb/s, 90k tbn,
 24 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: mp3, 44100 Hz, 2 channels, s16, 160 kb/s
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    :
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> flv)
  Stream #0:1 -> #0:1 (aac -> libmp3lame)
Press [q] to stop, [?] for help
frame=   26 fps=0.0 q=7.1 size=     350kB time=00:00:01.07 bitrate=2675.6kbits/s
frame=   79 fps= 77 q=31.0 size=     612kB time=00:00:03.26 bitrate=1535.2kbits/
frame=  132 fps= 85 q=24.8 size=    1005kB time=00:00:05.48 bitrate=1500.1kbits/
frame=  192 fps= 93 q=24.8 size=    1255kB time=00:00:07.96 bitrate=1290.7kbits/
frame=  255 fps= 99 q=31.0 size=    1504kB time=00:00:10.60 bitrate=1161.8kbits/
frame=  308 fps=100 q=31.0 size=    1913kB time=00:00:12.82 bitrate=1222.0kbits/
frame=  363 fps=101 q=31.0 size=    2333kB time=00:00:15.09 bitrate=1265.6kbits/
frame=  426 fps=103 q=31.0 size=    2547kB time=00:00:17.71 bitrate=1177.9kbits/
frame=  482 fps=104 q=31.0 size=    2876kB time=00:00:20.06 bitrate=1174.5kbits/
frame=  541 fps=105 q=31.0 size=    3130kB time=00:00:22.51 bitrate=1138.6kbits/
frame=  601 fps=106 q=31.0 size=    3410kB time=00:00:25.02 bitrate=1116.1kbits/
frame=  656 fps=106 q=31.0 size=    3783kB time=00:00:27.32 bitrate=1134.1kbits/
frame=  712 fps=106 q=31.0 size=    4103kB time=00:00:29.62 bitrate=1134.6kbits/
frame=  771 fps=107 q=31.0 size=    4397kB time=00:00:32.07 bitrate=1122.8kbits/
frame=  831 fps=107 q=31.0 size=    4650kB time=00:00:34.58 bitrate=1101.4kbits/
frame=  880 fps=107 q=31.0 size=    5053kB time=00:00:36.64 bitrate=1129.4kbits/
frame=  932 fps=106 q=31.0 size=    5474kB time=00:00:38.81 bitrate=1155.3kbits/
frame=  990 fps=107 q=31.0 size=    5758kB time=00:00:41.22 bitrate=1144.3kbits/
frame= 1046 fps=107 q=31.0 size=    6049kB time=00:00:43.54 bitrate=1138.0kbits/
frame= 1097 fps=106 q=31.0 size=    6464kB time=00:00:45.66 bitrate=1159.6kbits/
frame= 1146 fps=106 q=31.0 size=    6824kB time=00:00:47.72 bitrate=1171.3kbits/
frame= 1196 fps=105 q=31.0 size=    7159kB time=00:00:49.81 bitrate=1177.3kbits/
frame= 1251 fps=105 q=31.0 size=    7497kB time=00:00:52.12 bitrate=1178.3kbits/
frame= 1304 fps=105 q=31.0 size=    7883kB time=00:00:54.30 bitrate=1189.0kbits/
frame= 1348 fps=105 q=31.0 size=    8278kB time=00:00:56.13 bitrate=1208.0kbits/
frame= 1396 fps=104 q=31.0 size=    8680kB time=00:00:58.14 bitrate=1222.8kbits/
frame= 1448 fps=104 q=31.0 size=    9111kB time=00:01:00.31 bitrate=1237.5kbits/
frame= 1501 fps=104 q=31.0 size=    9430kB time=00:01:02.51 bitrate=1235.7kbits/
frame= 1553 fps=104 q=31.0 size=    9765kB time=00:01:04.70 bitrate=1236.3kbits/
frame= 1607 fps=104 q=31.0 size=   10062kB time=00:01:06.92 bitrate=1231.6kbits/
frame= 1661 fps=104 q=31.0 size=   10443kB time=00:01:09.19 bitrate=1236.3kbits/
frame= 1714 fps=104 q=31.0 size=   10742kB time=00:01:11.39 bitrate=1232.6kbits/
frame= 1763 fps=104 q=31.0 size=   11198kB time=00:01:13.45 bitrate=1248.8kbits/
frame= 1817 fps=104 q=31.0 size=   11566kB time=00:01:15.70 bitrate=1251.6kbits/
frame= 1870 fps=104 q=31.0 size=   11986kB time=00:01:17.89 bitrate=1260.5kbits/
frame= 1923 fps=104 q=31.0 size=   12246kB time=00:01:20.09 bitrate=1252.5kbits/
frame= 1976 fps=104 q=31.0 size=   12636kB time=00:01:22.31 bitrate=1257.6kbits/
frame= 2031 fps=104 q=31.0 size=   12943kB time=00:01:24.61 bitrate=1253.2kbits/
frame= 2086 fps=104 q=31.0 size=   13338kB time=00:01:26.90 bitrate=1257.3kbits/
frame= 2145 fps=104 q=31.0 size=   13630kB time=00:01:29.33 bitrate=1249.8kbits/
frame= 2202 fps=104 q=31.0 size=   13920kB time=00:01:31.71 bitrate=1243.3kbits/
frame= 2262 fps=104 q=31.0 size=   14240kB time=00:01:34.19 bitrate=1238.4kbits/
frame= 2310 fps=104 q=31.0 size=   14637kB time=00:01:36.20 bitrate=1246.3kbits/
frame= 2360 fps=104 q=31.0 size=   14975kB time=00:01:38.32 bitrate=1247.7kbits/
frame= 2412 fps=104 q=24.8 size=   15335kB time=00:01:40.46 bitrate=1250.4kbits/
frame= 2470 fps=104 q=31.0 size=   15613kB time=00:01:42.89 bitrate=1243.0kbits/
frame= 2532 fps=104 q=24.8 size=   15861kB time=00:01:45.48 bitrate=1231.8kbits/
frame= 2584 fps=104 q=31.0 size=   16233kB time=00:01:47.65 bitrate=1235.3kbits/
frame= 2631 fps=104 q=31.0 size=   16599kB time=00:01:49.60 bitrate=1240.5kbits/
frame= 2676 fps=104 q=24.8 size=   17007kB time=00:01:51.49 bitrate=1249.6kbits/
frame= 2721 fps=103 q=31.0 size=   17335kB time=00:01:53.37 bitrate=1252.6kbits/
frame= 2767 fps=103 q=31.0 size=   17721kB time=00:01:55.27 bitrate=1259.3kbits/
frame= 2813 fps=103 q=31.0 size=   18150kB time=00:01:57.20 bitrate=1268.5kbits/
frame= 2869 fps=103 q=31.0 size=   18535kB time=00:01:59.53 bitrate=1270.3kbits/
frame= 2915 fps=103 q=31.0 size=   18909kB time=00:02:01.44 bitrate=1275.5kbits/
frame= 2961 fps=103 q=31.0 size=   19290kB time=00:02:03.37 bitrate=1280.9kbits/
frame= 3013 fps=103 q=31.0 size=   19567kB time=00:02:05.49 bitrate=1277.3kbits/
frame= 3064 fps=102 q=31.0 size=   19886kB time=00:02:07.66 bitrate=1276.1kbits/
frame= 3116 fps=102 q=31.0 size=   20170kB time=00:02:09.80 bitrate=1272.9kbits/
frame= 3166 fps=102 q=31.0 size=   20585kB time=00:02:11.89 bitrate=1278.5kbits/
frame= 3218 fps=102 q=31.0 size=   20885kB time=00:02:14.08 bitrate=1276.0kbits/
frame= 3269 fps=102 q=31.0 size=   21277kB time=00:02:16.17 bitrate=1280.0kbits/
frame= 3323 fps=102 q=31.0 size=   21502kB time=00:02:18.44 bitrate=1272.3kbits/
frame= 3375 fps=102 q=31.0 size=   21871kB time=00:02:20.59 bitrate=1274.4kbits/
frame= 3424 fps=102 q=31.0 size=   22230kB time=00:02:22.65 bitrate=1276.6kbits/
frame= 3474 fps=102 q=31.0 size=   22649kB time=00:02:24.74 bitrate=1281.8kbits/
frame= 3528 fps=102 q=24.8 size=   22928kB time=00:02:26.99 bitrate=1277.8kbits/
frame= 3582 fps=102 q=31.0 size=   23313kB time=00:02:29.23 bitrate=1279.7kbits/
frame= 3635 fps=102 q=31.0 size=   23651kB time=00:02:31.43 bitrate=1279.5kbits/
frame= 3687 fps=102 q=31.0 size=   24056kB time=00:02:33.62 bitrate=1282.8kbits/
frame= 3744 fps=102 q=24.8 size=   24467kB time=00:02:36.00 bitrate=1284.8kbits/
frame= 3799 fps=102 q=31.0 size=   24789kB time=00:02:38.27 bitrate=1283.0kbits/
frame= 3853 fps=102 q=31.0 Lsize=   25407kB time=00:02:40.54 bitrate=1296.4kbits
/s
video:22162kB audio:3146kB global headers:0kB muxing overhead 0.386986%