gst-launch-0.8 -v --gst-debug-level=1 filesrc location="/tmp/3C22~High
Motion~MPEG-4, 128kbps, 30, 128x96~AMR-NB-FBR, 7950bps, 8000Hz, 16, Mono,
6s.3gp" ! spider ! ffcolorspace ! video/x-raw-rgb, bpp=32, depth=24 ! fakesink
WARNING: erroneous pipeline: could not link ffmpegcsp0 to fakesink0
         Trying to run anyway.
RUNNING pipeline ...
/pipeline0/filesrc0.src: caps = application/octet-stream
/pipeline0/spider0/sink_ident.sink: caps = application/octet-stream
/pipeline0/filesrc0.src: active = TRUE
/pipeline0/spider0/sink_ident.sink: active = TRUE
/pipeline0/spider0/sink_ident.src: active = TRUE
/pipeline0/spider0/src_0.sink: active = TRUE
/pipeline0/spider0/src_0.src: active = TRUE
/pipeline0/ffmpegcsp0.sink: active = TRUE
/pipeline0/ffmpegcsp0.src: active = TRUE
/pipeline0/fakesink0.sink: active = TRUE
/pipeline0/filesrc0.src: caps = video/quicktime
/pipeline0/spider0/sink_ident.sink: caps = video/quicktime
/pipeline0/spider0/sink_ident.src: caps = video/quicktime
/pipeline0/spider0/qtdemux0.sink: caps = video/quicktime
/pipeline0/spider0/qtdemux0.sink: active = TRUE
00000000 (0xb7303439): 00 00 00 00 00 00 00 00 00 18 ff ff 00 00 00 45 
...............E
00000010 (0xb7303449): 65 73 64 73 00 00 00 00 03 37 00 00 1f 04 2f 20 
esds.....7..../
00000020 (0xb7303459): 11 00 50 00 00 01 f4 00 00 01 f4 00 05 20 00 00 
..P.......... ..
00000030 (0xb7303469): 01 b0 08 00 00 01 b5 0e e0 40 c0 cf 00 00 01 00 
.........@......
00000040 (0xb7303479): 00 00 01 20 00 84 40 fa 28 20 20 60 a3 1f 06 01  ...
..@.(  `....
00000050 (0xb7303489): 02                                               .
/pipeline0/spider0/qtdemux0.audio_00: active = TRUE
/pipeline0/spider0/qtdemux0.video_00: active = TRUE
/pipeline0/spider0/qtdemux0.video_00: caps = video/mpeg, mpegversion=(int)4,
systemstream=(boolean)false, width=(int)128, height=(int)96, framerate=(double)30
/pipeline0/spider0/ffdec_mpeg40.sink: caps = video/mpeg, mpegversion=(int)4,
systemstream=(boolean)false, width=(int)128, height=(int)96, framerate=(double)30
/pipeline0/spider0/ffdec_mpeg40.sink: active = TRUE
/pipeline0/spider0/ffdec_mpeg40.src: active = TRUE
/pipeline0/spider0/src_0.src: caps = video/x-raw-yuv, width=(int)128,
height=(int)96, framerate=(double)30, format=(fourcc)I420
/pipeline0/ffmpegcsp0.sink: caps = video/x-raw-yuv, width=(int)128,
height=(int)96, framerate=(double)30, format=(fourcc)I420
/pipeline0/spider0/ffdec_mpeg40.src: caps = video/x-raw-yuv, width=(int)128,
height=(int)96, framerate=(double)30, format=(fourcc)I420
/pipeline0/spider0/src_0.sink: caps = video/x-raw-yuv, width=(int)128,
height=(int)96, framerate=(double)30, format=(fourcc)I420

works fine if we use ffmpegcolorspace instead of ffcolorspace or use 24bpp with
ffcolorspace.

Seem that ffcolorspace have diffculty in is link function to accept 32bpp.
I use version 0.8.6 of gst-ffmpeg plugin.