libavformat/utils: only run delta_dts_min calculation code when its value is used.

This should improve speed.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -3228,6 +3228,17 @@ int av_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out, AVPacket *pk
         ff_interleave_add_packet(s, pkt, ff_interleave_compare_dts);
     }
 
+    for(i=0; i < s->nb_streams; i++) {
+        if (s->streams[i]->last_in_packet_buffer) {
+            ++stream_count;
+        } else if(s->streams[i]->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
+            ++noninterleaved_count;
+        }
+    }
+
+    if (s->nb_streams == stream_count) {
+        flush = 1;
+    } else if (!flush){
         for(i=0; i < s->nb_streams; i++) {
             if (s->streams[i]->last_in_packet_buffer) {
                 int64_t delta_dts =
@@ -3238,21 +3249,14 @@ int av_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out, AVPacket *pk
                                 s->streams[s->packet_buffer->pkt.stream_index]->time_base,
                                 AV_TIME_BASE_Q);
                 delta_dts_min = FFMIN(delta_dts_min, delta_dts);
-            ++stream_count;
-        } else {
-            if(s->streams[i]->codec->codec_type == AVMEDIA_TYPE_SUBTITLE)
-                ++noninterleaved_count;
             }
         }
-
-    if (s->nb_streams == stream_count) {
-        flush = 1;
-    } else if (!flush &&
-             s->nb_streams == stream_count+noninterleaved_count &&
+        if(s->nb_streams == stream_count+noninterleaved_count &&
            delta_dts_min > 20*AV_TIME_BASE) {
             av_log(s, AV_LOG_DEBUG, "flushing with %d noninterleaved\n", noninterleaved_count);
             flush = 1;
         }
+    }
     if(stream_count && flush){
         pktl= s->packet_buffer;
         *out= pktl->pkt;