sorry my stupid question
the result
$this->bbcode_second_pass_code('', '(gdb) bt
#0 0x40345618 in h263_pred_motion (s=0xe71f0, block=0, dir=<value optimized out>, px=0x418abd70, py=0x418abd6c)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/h263.c:1723
#1 0x4034f568 in h263_encode_mb (s=0x3, block=0x11b0d0, motion_x=4, motion_y=2)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/h263.c:1309
#2 0x4029e9c8 in encode_thread (c=<value optimized out>, arg=<value optimized out>)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/mpegvideo_enc.c:1729
#3 0x402417a0 in avcodec_default_execute (c=0x40310, func=0x4029bb10 <encode_thread>, arg=0xe72bc, ret=0x3, count=1)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/utils.c:404
#4 0x4028fd98 in MPV_encode_picture (avctx=0x0, buf=0x3 <Address 0x3 out of bounds>,
buf_size=<value optimized out>, data=0x0)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/mpegvideo_enc.c:2921
#5 0x40242cb4 in avcodec_encode_video (avctx=0x40310, buf=0x42247008 "", buf_size=200000, pict=0x123ee0)
at /build/buildd-ffmpeg-debian_0.svn20080206-18+lenny3-arm-zlMAfF/ffmpeg-debian-0.svn20080206/libavcodec/utils.c:917
#6 0x00023c58 in ?? ()
Cannot access memory at address 0x0
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