Add an ability to retry rewind to the one before the last keyframe (#…

…5669)

- sometimes the rewind to one before the last keyframe leads
  to rewinding to this keyframe. With this change when it happens
  DALI tries to iteratively rewind to one before the last, two
  before the last, and so on...

Signed-off-by: Janusz Lisiecki <[email protected]>

dali/operators/reader/loader/video_loader.cc

@@ -564,6 +564,8 @@ void VideoLoader::read_file() {
 
   bool is_first_frame = true;
   int last_key_frame = -1;
+  int previous_last_key_frame = -1;
+  bool previous_last_key_frame_updated = false;
   bool key = false;
   bool seek_must_succeed = false;
   // how many key frames following the last requested frames we saw so far
@@ -607,18 +609,30 @@ void VideoLoader::read_file() {
                     "already 0");
         }
 
+      if (previous_last_key_frame < 0) {
+        previous_last_key_frame = last_key_frame - 1;
+        previous_last_key_frame_updated = true;
+      }
+      if (previous_last_key_frame_updated == false) {
+        --previous_last_key_frame;
+      }
       LOG_LINE << "Decoding not started, seek to preceding key frame, "
-                << "current frame " << frame
-                << ", last key frame " << last_key_frame
-                << ", is_key " << key << std::endl;
-      seek(file, last_key_frame - 1);
+               << "current frame " << frame
+               << ", look for a key frame before " << previous_last_key_frame
+               << ", is_key " << key << std::endl;
+      seek(file, previous_last_key_frame);
+      previous_last_key_frame_updated = false;
       frames_send = 0;
       last_key_frame = -1;
       continue;
     }
 
     if (key) {
       last_key_frame = frame;
+      if (frame < previous_last_key_frame) {
+        previous_last_key_frame = frame;
+        previous_last_key_frame_updated = true;
+      }
     }
 
     int pkt_frames = 1;