新增支持Python混合编程模式 (#4579)

src/Common/MultiMediaSourceMuxer.h

@@ -29,6 +29,7 @@ class MultiMediaSourceMuxer : public MediaSourceEventInterceptor, public MediaSi
 public:
     using Ptr = std::shared_ptr<MultiMediaSourceMuxer>;
     using RingType = toolkit::RingBuffer<Frame::Ptr>;
+    using onCreateMuxer = std::function<MediaSinkInterface::Ptr()>;
 
     class Listener {
     public:
@@ -249,6 +250,8 @@ private:
     toolkit::EventPoller::Ptr _poller;
     RingType::Ptr _ring;
 
+    MediaSinkInterface::Ptr _delegate;
+
     // 对象个数统计  [AUTO-TRANSLATED:3b43e8c2]
     // Object count statistics
     toolkit::ObjectStatistic<MultiMediaSourceMuxer> _statistic;