I used your command line with my copy of ffmpeg (bundled with Xuggler) and it produced perfect output. There were some warnings but it didn't affect the output.
E:\media\New>ffmpeg -i red5.flv -acodec libamr_nb -s 176x144 -ar 8000 -b 120000 -vcodec h263 -ab 10.
2k -ac 1 my.3gp
FFmpeg version SVN-r24930-xuggle-4.0.896, Copyright (c) 2000-2010 the FFmpeg developers
built on Aug 25 2010 23:41:31 with gcc 4.2.4 (TDM-1 for MinGW)
configuration: --prefix=/usr/xuggle --extra-version=xuggle-4.0.896 --extra-cflags=-I/usr/home/Paul
/code/trunk/java/xuggle-xuggler/build/native/i686-pc-mingw32/captive/usr/xuggle/include --extra-ldfl
ags=-L/usr/home/Paul/code/trunk/java/xuggle-xuggler/build/native/i686-pc-mingw32/captive/usr/xuggle/
lib --enable-shared --enable-gpl --enable-nonfree --enable-version3 --enable-libx264 --enable-libmp3
lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libopencore-amrnb --enable-lib
opencore-amrwb --extra-cflags=-mno-cygwin --extra-cflags=-fno-common --extra-ldflags=-mno-cygwin --e
xtra-ldflags=--out-implib --enable-w32threads --enable-memalign-hack
libavutil 50.24. 0 / 50.24. 0
libavcore 0. 6. 0 / 0. 6. 0
libavcodec 52.86. 1 / 52.86. 1
libavformat 52.78. 3 / 52.78. 3
libavdevice 52. 2. 1 / 52. 2. 1
libavfilter 1.38. 1 / 1.38. 1
libswscale 0.11. 0 / 0.11. 0
[flv @ 007d9f20] Estimating duration from bitrate, this may be inaccurate
Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 11.99 (12000/
1001)
Input #0, flv, from 'red5.flv':
Metadata:
duration : 1
width : 480
height : 360
videodatarate : 0
framerate : 12
videocodecid : 4
filesize : 27733
Duration: 00:00:01.33, start: 0.167000, bitrate: N/A
Stream #0.0: Video: vp6f, yuv420p, 480x368, 11.99 tbr, 1k tbn, 1k tbc
[buffer @ 007de2f0] w:480 h:368 pixfmt:yuv420p
[scale @ 007dee70] w:480 h:368 fmt:yuv420p -> w:176 h:144 fmt:yuv420p flags:0xa0000004
Output #0, 3gp, to 'my.3gp':
Metadata:
encoder : Lavf52.78.3
Stream #0.0: Video: h263, yuv420p, 176x144, q=2-31, 120 kb/s, 12k tbn, 11.99 tbc
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
[h263 @ 006cc200] warning, clipping 1 dct coefficients to -127..127
Last message repeated 10 times
[h263 @ 006cc200] warning, clipping 2 dct coefficients to -127..127
Last message repeated 1 times
[h263 @ 006cc200] warning, clipping 1 dct coefficients to -127..127
Last message repeated 3 times
[h263 @ 006cc200] warning, clipping 2 dct coefficients to -127..127
[h263 @ 006cc200] warning, clipping 1 dct coefficients to -127..127
[h263 @ 006cc200] warning, clipping 2 dct coefficients to -127..127
[h263 @ 006cc200] warning, clipping 1 dct coefficients to -127..127
frame= 13 fps= 0 q=1.6 Lsize= 24kB time=1.08 bitrate= 182.3kbits/s
video:23kB audio:0kB global headers:0kB muxing overhead 3.130478%