int diff= ptr ? ((char*)ptr)[-1] : 0;
int diff; if(!ptr) return av_malloc(size); diff= ((char*)ptr)[-1];
void *av_realloc(void *ptr, unsigned int size){#ifdef MEMALIGN_HACK    //FIXME this isnt aligned correctly though it probably isnt needed    int diff= ptr ? ((char*)ptr)[-1] : 0;    return realloc(ptr - diff, size + diff) + diff;#else    return realloc(ptr, size);#endif}