Handle IDX VobSub files with negative "delay" fields

ChangeLog

@@ -1,3 +1,8 @@
+2011-05-23  Moritz Bunkus  <moritz@bunkus.org>
+
+	* mkvmerge: enhancement: Added support for VobSub IDX files with
+	negative "delay" fields.
+
 2011-05-11  Moritz Bunkus  <moritz@bunkus.org>
 
 	* mkvmerge: bug fix: The 'doc type read version' EBML header field

src/input/r_vobsub.cpp

@@ -204,6 +204,7 @@ vobsub_reader_c::parse_headers() {
         }
       }
       track          = new vobsub_track_c(language);
+      delay          = 0;
       last_timestamp = 0;
       sort_required  = false;
       continue;
@@ -216,10 +217,16 @@ vobsub_reader_c::parse_headers() {
       line.erase(0, 6);
       strip(line);
 
+      int factor = 1;
+      if (!line.empty() && (line[0] == '-')) {
+        factor = -1;
+        line.erase(0, 1);
+      }
+
       int64_t timestamp;
       if (!parse_timecode(line, timestamp, true))
         mxerror_fn(m_ti.m_fname, boost::format(Y("line %1%: The 'delay' timestamp could not be parsed.\n")) % line_no);
-      delay = timestamp;
+      delay += timestamp * factor;
     }
 
     if ((7 == version) && starts_with_case(line, "timestamp:")) {
@@ -262,6 +269,13 @@ vobsub_reader_c::parse_headers() {
       entry.position  = filepos;
       entry.timestamp = timestamp * factor + delay;
 
+      if (   (0 >  delay)
+          && (0 != last_timestamp)
+          && (entry.timestamp < last_timestamp)) {
+        delay           += last_timestamp - entry.timestamp;
+        entry.timestamp  = last_timestamp;
+      }
+
       if (0 > entry.timestamp) {
         mxwarn_fn(m_ti.m_fname,
                   boost::format(Y("Line %1%: The line seems to be a subtitle entry but the timecode was negative even after adding the track "

tests/results.txt

@@ -140,3 +140,4 @@ T_290seven_bytes_aac_codec_data:d8680e35f0f6b595dce0fcb8af3b6e9e:passed:20110415
 T_291waveformatextensible:wav-avi:passed:20110415-124159:0.057127293
 T_292avi_aac_706d_privsize_huge:7b34a92c34461e869834e7db0c63ab97:passed:20110422-152313:0.042857788
 T_293aac_adif_misdetected_as_video:3:passed:20110426-091956:0.02536219
+T_294vobsub_negative_delay:6e1c59551b7ad05fa570bed2ffc926fe:passed:20110523-204847:1.41224474

tests/test-294vobsub_negative_delay.rb

@@ -0,0 +1,13 @@
+#!/usr/bin/ruby -w
+
+class T_294vobsub_negative_delay < Test
+  def description
+    "mkvmerge / VobSub with negative \"delay\" fields"
+  end
+
+  def run
+    merge "data/vobsub/House.S07E22.idx"
+    hash_tmp
+  end
+end
+