diff --git a/libavcodec/resample2.c b/libavcodec/resample2.c
index adda84435d..4c04c3edea 100644
--- a/libavcodec/resample2.c
+++ b/libavcodec/resample2.c
@@ -139,7 +139,7 @@ AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size,
     c->phase_mask= phase_count-1;
     c->linear= linear;
 
-    c->filter_length= FFMAX(ceil(filter_size/factor), 1);
+    c->filter_length= FFMAX((int)ceil(filter_size/factor), 1);
     c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
     av_build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, 1);
     memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 0940f652c4..32a4c92dce 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2188,20 +2188,24 @@ int av_write_header(AVFormatContext *s)
 
     /* init PTS generation */
     for(i=0;i<s->nb_streams;i++) {
+        int64_t den = AV_NOPTS_VALUE;
         st = s->streams[i];
 
         switch (st->codec->codec_type) {
         case CODEC_TYPE_AUDIO:
-            av_frac_init(&st->pts, 0, 0, 
-                         (int64_t)st->time_base.num * st->codec->sample_rate);
+            den = (int64_t)st->time_base.num * st->codec->sample_rate;
             break;
         case CODEC_TYPE_VIDEO:
-            av_frac_init(&st->pts, 0, 0, 
-                         (int64_t)st->time_base.num * st->codec->time_base.den);
+            den = (int64_t)st->time_base.num * st->codec->time_base.den;
             break;
         default:
             break;
         }
+        if (den != AV_NOPTS_VALUE) {
+            if (den <= 0)
+                return AVERROR_INVALIDDATA;
+            av_frac_init(&st->pts, 0, 0, den);
+        }
     }
     return 0;
 }