void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
{
    void **p = ptr;
    if (min_size < *size)
        return;
    min_size= FFMAX(17*min_size/16 + 32, min_size);
    av_free(*p);
    *p = av_malloc(min_size);
    if (!*p) min_size = 0;
    *size= min_size;
}