修复hls由于缓存导致花屏的问题

src/Extension/Frame.cpp

@@ -0,0 +1,42 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2016-2019 xiongziliang <771730766@qq.com>
+ *
+ * This file is part of ZLMediaKit(https://github.com/xiongziliang/ZLMediaKit).
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "Frame.h"
+
+using namespace std;
+using namespace toolkit;
+
+namespace mediakit{
+
+Frame::Ptr Frame::getCacheAbleFrame(const Frame::Ptr &frame){
+    if(frame->cacheAble()){
+        return frame;
+    }
+    return std::make_shared<FrameCacheAble>(frame);
+}
+
+}//namespace mediakit
+