printf("\n");
av_log(NULL, AV_LOG_ERROR, "\n");
static void dump(unsigned char *buf,size_t len){    int i;    for(i=0;i<len;i++) {        if ((i&15)==0) printf("%04x  ",i);        printf("%02x ",buf[i]);        if ((i&15)==15) printf("\n");    }    printf("\n");}