VIDEO: Support quicktime reverse playback with multiple edits

video/qt_decoder.cpp

@@ -499,6 +499,20 @@ const Graphics::Surface *QuickTimeDecoder::VideoTrackHandler::decodeNextFrame()
 		return 0;
 
 	if (_reversed) {
+		if (beforeCurEdit()) {
+			_curEdit--;
+
+			if (atFirstEdit()) {
+				return 0;
+			}
+
+			enterNewEditListEntry(false);
+			
+			if (isEmptyEdit()) {
+				return 0;
+			}
+		}
+
 		// Subtract one to place us on the frame before the current displayed frame.
 		_curFrame--;
 
@@ -885,10 +899,20 @@ uint32 QuickTimeDecoder::VideoTrackHandler::getCurEditTrackDuration() const {
 	return _parent->editList[_curEdit].trackDuration * _parent->timeScale / _decoder->_timeScale;
 }
 
+bool QuickTimeDecoder::VideoTrackHandler::atFirstEdit() const {
+    return _curEdit == 0;
+}
+
 bool QuickTimeDecoder::VideoTrackHandler::atLastEdit() const {
 	return _curEdit == _parent->editList.size();
 }
 
+bool QuickTimeDecoder::VideoTrackHandler::beforeCurEdit() const {
+    // We're at the end of the edit once the next frame's time would
+    // bring us past the end of the edit.
+    return getRateAdjustedFrameTime() <= getCurEditTimeOffset();
+}
+
 bool QuickTimeDecoder::VideoTrackHandler::endOfCurEdit() const {
 	// We're at the end of the edit once the next frame's time would
 	// bring us past the end of the edit.

video/qt_decoder.h

@@ -179,7 +179,9 @@ private:
 		uint32 getRateAdjustedFrameTime() const; // media time
 		uint32 getCurEditTimeOffset() const;     // media time
 		uint32 getCurEditTrackDuration() const;  // media time
+		bool atFirstEdit() const;
 		bool atLastEdit() const;
+		bool beforeCurEdit() const;
 		bool endOfCurEdit() const;
 		void checkEditListBounds();
 	};