for #367, design the config for exec.

@@ -935,7 +935,7 @@ vhost exec.srs.com {
         # other variables for exec only:
         #       [url] the rtmp url which trigger the publish.
         # @remark empty to ignore this exec.
-        publish     ./objs/ffmpeg/bin/ffmpeg -f flv -i [url] -vcodec copy -acodec copy -f flv ./[stream].flv;
+        publish     ./objs/ffmpeg/bin/ffmpeg -f flv -i [url] -c copy -y ./[stream].flv;
     }
 }