Cast to Chromcast and Video conversion

I use recent VLC player from Playstore 3.4.3 and when I try to cast to Chromecast I see this dialog,

and after this, the cast works properly 👍

I want to see the magic behind, but I don't find any text of this in code. Please can you point me to the right place in code where

• this problem is detected
• this healing magic happens.

Thank you !