avutil/opt: Fix parsing regression with constants starting with numbers

Fixes parsing "3dnow"

Found-by: jamrial
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/opt.c

@@ -206,44 +206,47 @@ static int set_string_number(void *obj, void *target_obj, const AVOption *o, con
         }
 
         {
-            const AVOption *o_named;
+            const AVOption *o_named = av_opt_find(target_obj, buf, o->unit, 0, 0);
             int res;
             int ci = 0;
             double const_values[64];
             const char * const_names[64];
-
-            if (o->unit) {
-                for (o_named = NULL; o_named = av_opt_next(target_obj, o_named); ) {
-                    if (o_named->type == AV_OPT_TYPE_CONST &&
-                        o_named->unit &&
-                        !strcmp(o_named->unit, o->unit)) {
-                        if (ci + 6 >= FF_ARRAY_ELEMS(const_values)) {
-                            av_log(obj, AV_LOG_ERROR, "const_values array too small for %s\n", o->unit);
-                            return AVERROR_PATCHWELCOME;
+            if (o_named && o_named->type == AV_OPT_TYPE_CONST)
+                d = DEFAULT_NUMVAL(o_named);
+            else {
+                if (o->unit) {
+                    for (o_named = NULL; o_named = av_opt_next(target_obj, o_named); ) {
+                        if (o_named->type == AV_OPT_TYPE_CONST &&
+                            o_named->unit &&
+                            !strcmp(o_named->unit, o->unit)) {
+                            if (ci + 6 >= FF_ARRAY_ELEMS(const_values)) {
+                                av_log(obj, AV_LOG_ERROR, "const_values array too small for %s\n", o->unit);
+                                return AVERROR_PATCHWELCOME;
+                            }
+                            const_names [ci  ] = o_named->name;
+                            const_values[ci++] = DEFAULT_NUMVAL(o_named);
                         }
-                        const_names [ci  ] = o_named->name;
-                        const_values[ci++] = DEFAULT_NUMVAL(o_named);
                     }
                 }
-            }
-            const_names [ci  ] = "default";
-            const_values[ci++] = DEFAULT_NUMVAL(o);
-            const_names [ci  ] = "max";
-            const_values[ci++] = o->max;
-            const_names [ci  ] = "min";
-            const_values[ci++] = o->min;
-            const_names [ci  ] = "none";
-            const_values[ci++] = 0;
-            const_names [ci  ] = "all";
-            const_values[ci++] = ~0;
-            const_names [ci] = NULL;
-            const_values[ci] = 0;
-
-            res = av_expr_parse_and_eval(&d, i ? buf : val, const_names,
-                                         const_values, NULL, NULL, NULL, NULL, NULL, 0, obj);
-            if (res < 0) {
-                av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\"\n", val);
-                return res;
+                const_names [ci  ] = "default";
+                const_values[ci++] = DEFAULT_NUMVAL(o);
+                const_names [ci  ] = "max";
+                const_values[ci++] = o->max;
+                const_names [ci  ] = "min";
+                const_values[ci++] = o->min;
+                const_names [ci  ] = "none";
+                const_values[ci++] = 0;
+                const_names [ci  ] = "all";
+                const_values[ci++] = ~0;
+                const_names [ci] = NULL;
+                const_values[ci] = 0;
+
+                res = av_expr_parse_and_eval(&d, i ? buf : val, const_names,
+                                            const_values, NULL, NULL, NULL, NULL, NULL, 0, obj);
+                if (res < 0) {
+                    av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\"\n", val);
+                    return res;
+                }
             }
         }
         if (o->type == AV_OPT_TYPE_FLAGS) {