fftools/ffmpeg: tweak sub2video_heartbeat() arguments

This function should not take an InputStream, as it only uses it to get
the InputFile and the timebase. Pass those directly instead and avoid
confusion over dealing with multiple InputStreams.

fftools/ffmpeg.c

@@ -252,9 +252,8 @@ void sub2video_update(InputStream *ist, int64_t heartbeat_pts,
     ist->sub2video.initialize = 0;
 }
 
-static void sub2video_heartbeat(InputStream *ist, int64_t pts)
+static void sub2video_heartbeat(InputFile *infile, int64_t pts, AVRational tb)
 {
-    InputFile *infile = input_files[ist->file_index];
     int i, j, nb_reqs;
     int64_t pts2;
 
@@ -268,7 +267,7 @@ static void sub2video_heartbeat(InputStream *ist, int64_t pts)
             continue;
         /* subtitles seem to be usually muxed ahead of other streams;
            if not, subtracting a larger time here is necessary */
-        pts2 = av_rescale_q(pts, ist->st->time_base, ist2->st->time_base) - 1;
+        pts2 = av_rescale_q(pts, tb, ist2->st->time_base) - 1;
         /* do not send the heartbeat frame if the subtitle is already ahead */
         if (pts2 <= ist2->sub2video.last_pts)
             continue;
@@ -1231,7 +1230,7 @@ static int process_input(int file_index)
 
     ist = ifile->streams[pkt->stream_index];
 
-    sub2video_heartbeat(ist, pkt->pts);
+    sub2video_heartbeat(ifile, pkt->pts, pkt->time_base);
 
     process_input_packet(ist, pkt, 0);