Thank you once again. The explanation on that thread led me to find this:
https://www.svp-team.com/wiki/SVP:MPC-HC

It solved my problem.

Chainik wrote:

it's all about MPC-HC / ffdshow settings, you need to enable ffdshow raw filter for webm files (if it's disabled for some reason)

Could you please give me directions on how to do that?

That's one less problem. Thanks Chainik.
I just noticed it doesn't to work on wmv files either.
But my main concern is regarding webm as it became really popular.

To add, it doesn't work for flv files either. Kinda expected but is there a way to get work on those and possibly gif files?

As the title says.  Anyone came across this problem?
Thanks in advance.