Add a loop range feature to MLT Producer

src/framework/mlt.vers

@@ -687,4 +687,9 @@ MLT_7.22.0 {
     mlt_property_is_color;
     mlt_property_is_numeric;
     mlt_property_is_rect;
-} MLT_7.18.0;
+} MLT_7.18.0;
+
+MLT_7.24.0 {
+  global:
+    mlt_producer_set_loop_range;
+} MLT_7.22.0;

src/framework/mlt_producer.c

@@ -356,6 +356,14 @@ int mlt_producer_seek(mlt_producer self, mlt_position position)
         // Do not bounds check a link.
     } else if (position < 0 || mlt_producer_get_playtime(self) == 0) {
         position = 0;
+    } else if (mlt_properties_exists(MLT_PRODUCER_PROPERTIES(self), "_loop_start")) {
+        int loopStart = mlt_properties_get_int(MLT_PRODUCER_PROPERTIES(self), "_loop_start");
+        int loopEnd = mlt_properties_get_int(MLT_PRODUCER_PROPERTIES(self), "_loop_end");
+        if (loopStart >= 0 && loopEnd > 0 && loopStart < loopEnd) {
+            if (position > loopEnd || position < loopStart) {
+                position = loopStart;
+            }
+        }
     } else if (use_points && (eof == NULL || !strcmp(eof, "pause"))
                && position >= mlt_producer_get_playtime(self)) {
         mlt_producer_set_speed(self, 0);
@@ -1304,3 +1312,28 @@ int mlt_producer_probe(mlt_producer self)
     }
     return 0;
 }
+
+/** Set the loop range for the producer.
+ *
+ * When the loop range is set, the producer will automatically seek to the start frame
+ * after it provides the end frame. Set start to -1 to disable looping.
+ *
+ * \public \memberof mlt_producer_s
+ * \param self a producer
+ * \param start the frame number for the beginning of the loop
+ * \param end the frame number for the end of the loop
+ */
+
+void mlt_producer_set_loop_range(mlt_producer self, int start, int end)
+{
+    if (!self)
+        return;
+    mlt_properties properties = MLT_PRODUCER_PROPERTIES(self);
+    if (start < 0 || end < 0) {
+        mlt_properties_clear(properties, "_loop_start");
+        mlt_properties_clear(properties, "_loop_end");
+    } else {
+        mlt_properties_set_int(properties, "_loop_start", start);
+        mlt_properties_set_int(properties, "_loop_end", end);
+    }
+}

src/framework/mlt_producer.h

@@ -145,5 +145,6 @@ extern void mlt_producer_close(mlt_producer self);
 int64_t mlt_producer_get_creation_time(mlt_producer self);
 void mlt_producer_set_creation_time(mlt_producer self, int64_t creation_time);
 extern int mlt_producer_probe(mlt_producer self);
+extern void mlt_producer_set_loop_range(mlt_producer self, int start, int end);
 
 #endif

src/mlt++/MltProducer.cpp

@@ -266,3 +266,8 @@ bool Producer::probe()
 {
     return mlt_producer_probe(get_producer());
 }
+
+void Producer::set_loop_range(int start, int end)
+{
+    return mlt_producer_set_loop_range(get_producer(), start, end);
+}

src/mlt++/MltProducer.h

@@ -78,6 +78,7 @@ class MLTPP_DECLSPEC Producer : public Service
     int64_t get_creation_time();
     void set_creation_time(int64_t creation_time);
     bool probe();
+    void set_loop_range(int start, int end);
 };
 } // namespace Mlt
 

src/mlt++/mlt++.vers

@@ -733,3 +733,10 @@ MLT_7.14.0 {
       "Mlt::Chain::attach_normalizers()";
     };
 } MLT_7.12.0;
+
+MLT_7.24.0 {
+  global:
+    extern "C++" {
+      "Mlt::Producer::set_loop_range(int, int)";
+    };
+} MLT_7.14.0;