Make sure that start_display_time is 0 by moving its value onto pts.

If it was not 0, subtitle encoding would fail.

Originally committed as revision 19710 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -826,6 +826,10 @@ static void do_subtitle_out(AVFormatContext *s,
 
     for(i = 0; i < nb; i++) {
         sub->pts = av_rescale_q(pts, ist->st->time_base, AV_TIME_BASE_Q);
+        // start_display_time is required to be 0
+        sub->pts              += av_rescale_q(sub->start_display_time, (AVRational){1, 1000}, AV_TIME_BASE_Q);
+        sub->end_display_time -= sub->start_display_time;
+        sub->start_display_time = 0;
         subtitle_out_size = avcodec_encode_subtitle(enc, subtitle_out,
                                                     subtitle_out_max_size, sub);
         if (subtitle_out_size < 0) {
@@ -837,7 +841,7 @@ static void do_subtitle_out(AVFormatContext *s,
         pkt.stream_index = ost->index;
         pkt.data = subtitle_out;
         pkt.size = subtitle_out_size;
-        pkt.pts = av_rescale_q(pts, ist->st->time_base, ost->st->time_base);
+        pkt.pts = av_rescale_q(sub->pts, AV_TIME_BASE_Q, ost->st->time_base);
         if (enc->codec_id == CODEC_ID_DVB_SUBTITLE) {
             /* XXX: the pts correction is handled here. Maybe handling
                it in the codec would be better */