Update README.md

Former-commit-id: 565f74a830

README.md

@@ -56,6 +56,8 @@ Long term, the aim is for the toolchain to also be able to optionally push to a
 Troubleshooting:
 ================
 
+Make sure you have enough RAM and CPU. Only lowercase file extension supported now.
+
 If you run ODM with your own camera, it is possible you will see something like this:
 
 ```