avformat/mpegtsenc: fix first_pcr initial update

Commit 6f36eb0da7 claim it fixes endless loop on
package generation if muxrate specified and copyts used. But actually it does
not work properly if -mpegts_copyts 1 is specified:

ffmpeg -y -copyts -i loewe.ts -c:v libx264 -x264opts nal-hrd=cbr:force-cfr=1 -b:v 3500k -minrate 3500k -maxrate 3500k -bufsize 1000k  -c:a mp2 -f mpegts -mpegts_copyts 1 -muxrate 4500k -vframes 1000 test.ts

ffmpeg generate huge file until it reach zero-based pcr value equal to first dts.

Attached patch fixes it.

Reviewed-by: Limin Wang <lance.lmwang@gmail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/mpegtsenc.c

@@ -1852,12 +1852,12 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
     if (side_data)
         stream_id = side_data[0];
 
-    if (ts->copyts < 1) {
-        if (!ts->first_dts_checked && dts != AV_NOPTS_VALUE) {
-            ts->first_pcr += dts * 300;
-            ts->first_dts_checked = 1;
-        }
+    if (!ts->first_dts_checked && dts != AV_NOPTS_VALUE) {
+        ts->first_pcr += dts * 300;
+        ts->first_dts_checked = 1;
+    }
 
+    if (ts->copyts < 1) {
         if (pts != AV_NOPTS_VALUE)
             pts += delay;
         if (dts != AV_NOPTS_VALUE)