Fix T53003: IMB: Invalid framerate handling due to short integer overflow.

FFMPEG uses int for the numerator, while Blender uses a short. So in
cases people gave weird exotic framerate values and we cannot reduce
enough the numerator, we'd get totally weird values (even negative frame
rates sometimes!)

Now we add checks for short overflow and approximate as best as possible
in that case (error should not matter unless you have shots of at least
several hundreds of hours ;) ).

2 files changed, 19 insertions, 5 deletions

diff --git a/source/blender/imbuf/intern/IMB_anim.h b/source/blender/imbuf/intern/IMB_anim.h
index 6d7ad7985f9..5f47769074d 100644
--- a/source/blender/imbuf/intern/IMB_anim.h
+++ b/source/blender/imbuf/intern/IMB_anim.h
@@ -105,8 +105,8 @@ struct anim {
 	int curtype;
 	int curposition;    /* index  0 = 1e,  1 = 2e, enz. */
 	int duration;
-	short frs_sec;
-	float frs_sec_base;
+	int frs_sec;
+	double frs_sec_base;
 	int x, y;
 	
 	/* for number */
diff --git a/source/blender/imbuf/intern/anim_movie.c b/source/blender/imbuf/intern/anim_movie.c
index 5bb91efe186..dc534f18257 100644
--- a/source/blender/imbuf/intern/anim_movie.c
+++ b/source/blender/imbuf/intern/anim_movie.c
@@ -55,6 +55,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <math.h>
+#include <limits.h>
 #ifndef _WIN32
 #include <dirent.h>
 #else
@@ -1398,15 +1399,28 @@ int IMB_anim_get_duration(struct anim *anim, IMB_Timecode_Type tc)
 bool IMB_anim_get_fps(struct anim *anim,
                      short *frs_sec, float *frs_sec_base, bool no_av_base)
 {
+	double frs_sec_base_double;
 	if (anim->frs_sec) {
-		*frs_sec = anim->frs_sec;
-		*frs_sec_base = anim->frs_sec_base;
+		if (anim->frs_sec > SHRT_MAX) {
+			/* We cannot store original rational in our short/float format,
+			 * we need to approximate it as best as we can... */
+			*frs_sec = SHRT_MAX;
+			frs_sec_base_double = anim->frs_sec_base * (double)SHRT_MAX / (double)anim->frs_sec;
+		}
+		else {
+			*frs_sec = anim->frs_sec;
+			frs_sec_base_double = anim->frs_sec_base;
+		}
 #ifdef WITH_FFMPEG
 		if (no_av_base) {
-			*frs_sec_base /= AV_TIME_BASE;
+			*frs_sec_base = (float)(frs_sec_base_double / AV_TIME_BASE);
+		}
+		else {
+			*frs_sec_base = (float)frs_sec_base_double;
 		}
 #else
 		UNUSED_VARS(no_av_base);
+		*frs_sec_base = (float)frs_sec_base_double;
 #endif
 		return true;
 	}