static const AVOption options[]={
{"b", "set video bitrate (in bits/s)", OFFSET(bit_rate), FF_OPT_TYPE_INT, AV_CODEC_DEFAULT_BITRATE, INT_MIN, INT_MAX, V|A|E},
-{"bt", "set video bitrate tolerance (in bits/s)", OFFSET(bit_rate_tolerance), FF_OPT_TYPE_INT, AV_CODEC_DEFAULT_BITRATE*20, INT_MIN, INT_MAX, V|E},
+{"bt", "set video bitrate tolerance (in bits/s)", OFFSET(bit_rate_tolerance), FF_OPT_TYPE_INT, AV_CODEC_DEFAULT_BITRATE*20, 1, INT_MAX, V|E},
{"flags", NULL, OFFSET(flags), FF_OPT_TYPE_FLAGS, DEFAULT, INT_MIN, INT_MAX, V|A|E|D, "flags"},
{"mv4", "use four motion vector by macroblock (mpeg4)", 0, FF_OPT_TYPE_CONST, CODEC_FLAG_4MV, INT_MIN, INT_MAX, V|E, "flags"},
{"obmc", "use overlapped block motion compensation (h263+)", 0, FF_OPT_TYPE_CONST, CODEC_FLAG_OBMC, INT_MIN, INT_MAX, V|E, "flags"},