avfilter/af_astats: do not clear previous sample value

Should help when using reset=1 and metadata=1
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/af_astats.c

@@ -98,14 +98,27 @@ static void reset_stats(AudioStatsContext *s)
 {
     int c;
 
-    memset(s->chstats, 0, sizeof(*s->chstats) * s->nb_channels);
-
     for (c = 0; c < s->nb_channels; c++) {
         ChannelStats *p = &s->chstats[c];
 
         p->min = p->min_sigma_x2 = DBL_MAX;
         p->max = p->max_sigma_x2 = DBL_MIN;
-        p->min_diff = p->max_diff = -1;
+        p->min_diff = DBL_MAX;
+        p->max_diff = DBL_MIN;
+        p->sigma_x = 0;
+        p->sigma_x2 = 0;
+        p->avg_sigma_x2 = 0;
+        p->min_sigma_x2 = 0;
+        p->max_sigma_x2 = 0;
+        p->min_run = 0;
+        p->max_run = 0;
+        p->min_runs = 0;
+        p->max_runs = 0;
+        p->diff1_sum = 0;
+        p->mask = 0;
+        p->min_count = 0;
+        p->max_count = 0;
+        p->nb_samples = 0;
     }
 }
 
@@ -164,8 +177,8 @@ static inline void update_stat(AudioStatsContext *s, ChannelStats *p, double d)
     p->sigma_x += d;
     p->sigma_x2 += d * d;
     p->avg_sigma_x2 = p->avg_sigma_x2 * s->mult + (1.0 - s->mult) * d * d;
-    p->min_diff = FFMIN(p->min_diff == -1 ? DBL_MAX : p->min_diff, fabs(d - (p->min_diff == -1 ? DBL_MAX : p->last)));
-    p->max_diff = FFMAX(p->max_diff, fabs(d - (p->max_diff == -1 ? d : p->last)));
+    p->min_diff = FFMIN(p->min_diff, fabs(d - p->last));
+    p->max_diff = FFMAX(p->max_diff, fabs(d - p->last));
     p->diff1_sum += fabs(d - p->last);
     p->last = d;
     p->mask |= llrint(d * (UINT64_C(1) << 63));