Add rounding margin to the subtitle time search

In case the subtitle times are not already set to exact frame times, this extra rounding margin will round to the nearest frame. This Could happen if the SRT subtitles were originally timed for a different frame rate.
mltframework · Aug 13, 2024 · 017dd93 · 017dd93
1 parent 884ef05
commit 017dd93
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Showing 4 changed files with 16 additions and 9 deletions.
diff --git a/src/modules/plus/filter_subtitle.cpp b/src/modules/plus/filter_subtitle.cpp
@@ -121,7 +121,8 @@ static mlt_frame filter_process(mlt_filter filter, mlt_frame frame)
         int64_t frameMs = (int64_t) mlt_frame_get_position(frame) * 1000 * profile->frame_rate_den
                           / profile->frame_rate_num;
         int prevIndex = mlt_properties_get_int(properties, "_prevIndex");
-        int index = Subtitles::indexForTime(subtitles, frameMs, prevIndex);
+        int marginMs = 999 * profile->frame_rate_den / profile->frame_rate_num;
+        int index = Subtitles::indexForTime(subtitles, frameMs, prevIndex, marginMs);
         if (index > -1) {
             text = subtitles[index].text.c_str();
             mlt_properties_set_int(properties, "_prevIndex", index);

diff --git a/src/modules/plus/filter_subtitle_feed.cpp b/src/modules/plus/filter_subtitle_feed.cpp
@@ -120,7 +120,8 @@ static mlt_frame filter_process(mlt_filter filter, mlt_frame frame)
     int64_t frameMs = (int64_t) mlt_frame_get_position(frame) * 1000 * profile->frame_rate_den
                       / profile->frame_rate_num;
     int prevIndex = mlt_properties_get_int(properties, "_prevIndex");
-    int index = Subtitles::indexForTime(subtitles, frameMs, prevIndex);
+    int marginMs = 999 * profile->frame_rate_den / profile->frame_rate_num;
+    int index = Subtitles::indexForTime(subtitles, frameMs, prevIndex, marginMs);
     if (index > -1) {
         mlt_properties_set_int(properties, "_prevIndex", index);
     }

diff --git a/src/modules/plus/subtitles/subtitles.cpp b/src/modules/plus/subtitles/subtitles.cpp
@@ -153,33 +153,38 @@ bool Subtitles::writeToSrtString(std::string &text, const Subtitles::SubtitleVec
     return writeToSrtStream(textStream, items);
 }
 
-int Subtitles::indexForTime(const Subtitles::SubtitleVector &items, int64_t msTime, int searchStart)
+int Subtitles::indexForTime(const Subtitles::SubtitleVector &items,
+                            int64_t msTime,
+                            int searchStart,
+                            int msMargin)
 {
     // Return -1 if there is no subtitle for the time.
     int index = -1;
     int count = (int) items.size();
     if (count == 0) {
         // Nothing to search
-    } else if (count > 0 && items[0].start > msTime) {
+    } else if (count > 0 && (items[0].start - msMargin) > msTime) {
         // No text if before the first item;
     } else if (count > 1 && items[count - 1].end < msTime) {
         // No text if after the last item;
-    } else if (searchStart > -1 && searchStart < count && items[searchStart].start <= msTime
+    } else if (searchStart > -1 && searchStart < count
+               && (items[searchStart].start - msMargin) <= msTime
                && items[searchStart].end >= msTime) {
         // First see if this is the same as the last subtitle
         index = searchStart;
     } else if (searchStart > -1 && (searchStart + 1) < count && items[searchStart].end < msTime
-               && items[searchStart + 1].start > msTime) {
+               && (items[searchStart + 1].start - msMargin) > msTime) {
         // No text if between the previous and next subtitle
     } else if (searchStart > -1 && (searchStart + 1) < count
-               && items[searchStart + 1].start <= msTime && items[searchStart + 1].end >= msTime) {
+               && (items[searchStart + 1].start - msMargin) <= msTime
+               && items[searchStart + 1].end >= msTime) {
         // See if this is the next subtitle
         index = searchStart + 1;
     } else {
         // Perform a full search from the beginning
         int i = 0;
         for (i = 0; i < count; i++) {
-            if (items[i].start <= msTime && items[i].end >= msTime) {
+            if ((items[i].start - msMargin) <= msTime && items[i].end >= msTime) {
                 index = i;
                 break;
             } else if (items[i].end > msTime) {

diff --git a/src/modules/plus/subtitles/subtitles.h b/src/modules/plus/subtitles/subtitles.h
@@ -37,7 +37,7 @@ SubtitleVector readFromSrtFile(const std::string &path);
 bool writeToSrtFile(const std::string &path, const SubtitleVector &items);
 SubtitleVector readFromSrtString(const std::string &text);
 bool writeToSrtString(std::string &text, const SubtitleVector &items);
-int indexForTime(const SubtitleVector &items, int64_t msTime, int searchStart);
+int indexForTime(const SubtitleVector &items, int64_t msTime, int searchStart, int msMargin);
 } // namespace Subtitles
 
 #endif // SUBTITLES_H