if ((ret = avformat_open_input(&avf, filename, NULL, NULL)) < 0) {
fprintf(stderr, "%s: %s\n", filename, av_err2str(ret));
return 1;
if ((ret = avformat_open_input(&avf, filename, NULL, NULL)) < 0) {
fprintf(stderr, "%s: %s\n", filename, av_err2str(ret));
return 1;