fprintf(stderr, "Can't initialize DV format!\n"
av_log(s, AV_LOG_ERROR, "Can't initialize DV format!\n"
static int dv_write_header(AVFormatContext *s){    s->priv_data = dv_init_mux(s);    if (!s->priv_data) {        fprintf(stderr, "Can't initialize DV format!\n"		    "Make sure that you supply exactly two streams:\n"		    "     video: 25fps or 29.97fps, audio: 2ch/48Khz/PCM\n");	return -1;    }    return 0;}