better handling of float cli arguments

v4l2/grabvidseq.c

@@ -122,7 +122,14 @@ while ((opt = getopt(argc, argv, "d:ghn:o:O:p:s:uv")) != -1) {
 		case 'n':	nbre_capt = atoi(optarg);	break;
 		case 'O':	dest_dir = optarg;		break;
 		case 'o':	outfile = optarg;		break;
-		case 'p':	period = 1e6*atof(optarg);	break;
+		case 'p':	foo = parse_double(optarg, &period);
+				if (foo<0) {
+					fprintf(stderr,
+						"error parsing -p arg '%s'\n",
+						optarg);
+					exit(1);
+					}
+				break;
 		case 's':	parse_WxH(optarg, &width, &height);
 				break;
 		case 'u':	upscaling = 1;			break;