vf_fps: use double constants for default/min/max for start_time

When using AV_NOPTS_VALUE (which expands to INT64_C(0x8000000000000000))
as union initializer for a double field, the c99 converter needs to
interpret this constant when filling the union initializer, and it is
interpreted as a positive value.

When converting AV_NOPTS_VALUE to a double, MSVC 2010 ends up with
the same positive value as the c99 converter, while MSVC 2012 gets
a negative value.

This results in an infite loop in various FATE tests on MSVC 2012.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavfilter/vf_fps.c

@@ -21,6 +21,8 @@
  * a filter enforcing given constant framerate
  */
 
+#include <float.h>
+
 #include "libavutil/common.h"
 #include "libavutil/fifo.h"
 #include "libavutil/mathematics.h"
@@ -56,7 +58,7 @@ typedef struct FPSContext {
 #define V AV_OPT_FLAG_VIDEO_PARAM
 static const AVOption options[] = {
     { "fps", "A string describing desired output framerate", OFFSET(fps), AV_OPT_TYPE_STRING, { .str = "25" }, .flags = V },
-    { "start_time", "Assume the first PTS should be this value.", OFFSET(start_time), AV_OPT_TYPE_DOUBLE, { .dbl = AV_NOPTS_VALUE}, INT64_MIN, INT64_MAX, V },
+    { "start_time", "Assume the first PTS should be this value.", OFFSET(start_time), AV_OPT_TYPE_DOUBLE, { .dbl = DBL_MAX}, -DBL_MAX, DBL_MAX, V },
     { NULL },
 };
 
@@ -181,7 +183,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
             if (ret < 0)
                 return ret;
 
-            if (s->start_time != AV_NOPTS_VALUE) {
+            if (s->start_time != DBL_MAX) {
                 double first_pts = s->start_time * AV_TIME_BASE;
                 first_pts = FFMIN(FFMAX(first_pts, INT64_MIN), INT64_MAX);
                 s->first_pts = s->pts = av_rescale_q(first_pts, AV_TIME_BASE_Q,