ismindex: Calculate the file duration among the included tracks

If the input file contains other tracks (non video/audio) that
aren't included in ismindex, the global file duration as returned
by libavformat might not be equal to the maximum of the duration
of the actual included tracks.
Signed-off-by: Martin Storsjö <martin@martin.st>

tools/ismindex.c

@@ -292,8 +292,6 @@ static int handle_file(struct Tracks *tracks, const char *file, int split)
         fprintf(stderr, "No streams found in %s\n", file);
         goto fail;
     }
-    if (!tracks->duration)
-        tracks->duration = ctx->duration;
 
     for (i = 0; i < ctx->nb_streams; i++) {
         struct Track **temp;
@@ -332,6 +330,10 @@ static int handle_file(struct Tracks *tracks, const char *file, int split)
             continue;
         }
 
+        tracks->duration = FFMAX(tracks->duration,
+                                 av_rescale_rnd(track->duration, AV_TIME_BASE,
+                                                track->timescale, AV_ROUND_UP));
+
         if (track->is_audio) {
             if (tracks->audio_track < 0)
                 tracks->audio_track = tracks->nb_tracks;