新增媒体流flush机制：#1996

src/Rtp/GB28181Process.h

@@ -26,7 +26,7 @@ class GB28181Process : public ProcessInterface {
 public:
     typedef std::shared_ptr<GB28181Process> Ptr;
     GB28181Process(const MediaInfo &media_info, MediaSinkInterface *sink);
-    ~GB28181Process() override;
+    ~GB28181Process() override = default;
 
     /**
      * 输入rtp
@@ -36,6 +36,11 @@ public:
      */
     bool inputRtp(bool, const char *data, size_t data_len) override;
 
+    /**
+     * 刷新输出所有缓存
+     */
+    void flush() override;
+
 protected:
     void onRtpSorted(RtpPacket::Ptr rtp);