ffmpeg.c: count subtitles in total size.

This avoids the "Output file is empty" warning
with subtitles-only files.

ffmpeg.c

@@ -163,6 +163,7 @@ static int run_as_daemon  = 0;
 static volatile int received_nb_signals = 0;
 static int64_t video_size = 0;
 static int64_t audio_size = 0;
+static int64_t subtitle_size = 0;
 static int64_t extra_size = 0;
 static int nb_frames_dup = 0;
 static int nb_frames_drop = 0;
@@ -1688,6 +1689,7 @@ static void do_subtitle_out(AVFormatContext *s,
                 pkt.pts += 90 * sub->end_display_time;
         }
         write_frame(s, &pkt, ost);
+        subtitle_size += pkt.size;
     }
 }
 
@@ -2123,15 +2125,16 @@ static void print_report(int is_last_report, int64_t timer_start, int64_t cur_ti
     fflush(stderr);
 
     if (is_last_report) {
-        int64_t raw= audio_size + video_size + extra_size;
+        int64_t raw= audio_size + video_size + subtitle_size + extra_size;
         av_log(NULL, AV_LOG_INFO, "\n");
-        av_log(NULL, AV_LOG_INFO, "video:%1.0fkB audio:%1.0fkB global headers:%1.0fkB muxing overhead %f%%\n",
+        av_log(NULL, AV_LOG_INFO, "video:%1.0fkB audio:%1.0fkB subtitle:%1.0f global headers:%1.0fkB muxing overhead %f%%\n",
                video_size / 1024.0,
                audio_size / 1024.0,
+               subtitle_size / 1024.0,
                extra_size / 1024.0,
                100.0 * (total_size - raw) / raw
         );
-        if(video_size + audio_size + extra_size == 0){
+        if(video_size + audio_size + subtitle_size + extra_size == 0){
             av_log(NULL, AV_LOG_WARNING, "Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)\n");
         }
     }
@@ -2253,6 +2256,8 @@ static void do_streamcopy(InputStream *ist, OutputStream *ost, const AVPacket *p
     else if (ost->st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
         video_size += pkt->size;
         ost->sync_opts++;
+    } else if (ost->st->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) {
+        subtitle_size += pkt->size;
     }
 
     if (pkt->pts != AV_NOPTS_VALUE)