[FFmpeg-devel] [PATCH 1/2] avfilter/vf_gblur: fix divide by zero

[quinkblack at foxmail.com]

From: Zhao Zhili <zhilizhao at tencent.com>

./ffmpeg -i ~/Pictures/test.jpg -vf 'gblur=sigma=0' -f null -
...
src/libavfilter/vf_gblur.c:260:59: runtime error: division by zero
src/libavfilter/vf_gblur.c:261:26: runtime error: division by zero
---
 libavfilter/vf_gblur.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/libavfilter/vf_gblur.c b/libavfilter/vf_gblur.c
index 2e587f6a0a..e057937fb7 100644
--- a/libavfilter/vf_gblur.c
+++ b/libavfilter/vf_gblur.c
@@ -37,11 +37,17 @@
 #define OFFSET(x) offsetof(GBlurContext, x)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
 
+/* Consider the three-sigma rule, for minimum radius of 1 sigma should not
+ * be smaller than 1/3. Relax it to 0.25 if the user want to try.
+ */
+#define SIGMA_MIN   0.25
+#define SIGMA_MAX   1024.0
+
 static const AVOption gblur_options[] = {
-    { "sigma",  "set sigma",            OFFSET(sigma),  AV_OPT_TYPE_FLOAT, {.dbl=0.5}, 0.0, 1024, FLAGS },
+    { "sigma",  "set sigma",            OFFSET(sigma),  AV_OPT_TYPE_FLOAT, {.dbl=0.5},  SIGMA_MIN, SIGMA_MAX, FLAGS },
     { "steps",  "set number of steps",  OFFSET(steps),  AV_OPT_TYPE_INT,   {.i64=1},     1,    6, FLAGS },
     { "planes", "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT,   {.i64=0xF},   0,  0xF, FLAGS },
-    { "sigmaV", "set vertical sigma",   OFFSET(sigmaV), AV_OPT_TYPE_FLOAT, {.dbl=-1},   -1, 1024, FLAGS },
+    { "sigmaV", "set vertical sigma",   OFFSET(sigmaV), AV_OPT_TYPE_FLOAT, {.dbl=-1},   -1, SIGMA_MAX, FLAGS },
     { NULL }
 };
 
@@ -244,7 +250,7 @@ static int config_input(AVFilterLink *inlink)
     if (!s->buffer)
         return AVERROR(ENOMEM);
 
-    if (s->sigmaV < 0) {
+    if (s->sigmaV < SIGMA_MIN) {
         s->sigmaV = s->sigma;
     }
     ff_gblur_init(s);
-- 
2.22.0