ffmpeg set_number函数

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static int set_number(void *obj, const char *name, double num, int den, int64_t intnum,

int search_flags) //其中intnum是从options的default_val里读取的

{

void *dst, *target_obj;

const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);

if (!o || !target_obj)

return AVERROR_OPTION_NOT_FOUND;

dst = ((uint8_t*)target_obj) + o->offset;

return write_number(obj, o, dst, num, den, intnum);

}

其中 target_obj=obj 然后dst =target_obj

write_number函数里的

case AV_OPT_TYPE_FLAGS:

case AV_OPT_TYPE_INT: *(int *)dst= llrint(num/den)*intnum; break;

case AV_OPT_TYPE_INT64: *(int64_t *)dst= llrint(num/den)*intnum; break;

case AV_OPT_TYPE_FLOAT: *(float *)dst= num*intnum/den; break;

case AV_OPT_TYPE_DOUBLE:*(double *)dst= num*intnum/den; break;

case AV_OPT_TYPE_RATIONAL:

floor()和ceil()函数

floor(2.5)=2小于或者等于最大整数

floor(-2.5)=-3

ceil(2.5)=3大于x的最小整数

ceil(-2.5)=-2

av_opt_nextav_opt_next返回的是AVOption*

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