p++;
static int sdp_probe(AVProbeData *p1){    const char *p;    /* we look for a line beginning "c=IN IP4" */    p = p1->buf;    while (*p != '\0') {        if (strstart(p, "c=IN IP4", NULL))            return AVPROBE_SCORE_MAX / 2;        p = strchr(p, '\n');        if (!p)            break;        p++;        if (*p == '\r')            p++;    }    return 0;}