sout: sdi: fully drain the video filter when the input source changes

modules/stream_out/sdi/SDIStream.cpp

@@ -573,7 +573,16 @@ void VideoDecodedStream::Output(picture_t *p_pic)
                 (char*)&p_owner->decoder_out.i_codec);
 
         if(p_filters_chain)
+        {
+            for (;;)
+            {
+                picture_t *drained = filter_chain_VideoDrain(p_filters_chain, true);
+                if (drained == NULL)
+                    break;
+                outputbuffer->Enqueue(drained);
+            }
             filter_chain_Delete(p_filters_chain);
+        }
         p_filters_chain = VideoFilterCreate(&p_owner->decoder_out,
                                             picture_GetVideoContext(p_pic));
         if(!p_filters_chain)