WebView on ionic 4

Webview does seem to work for me, and I cannot find solution on the web:
this.webView.convertFileSrc(url); returns undefined/app_file/…
the rest of the file is correct. I want to load local videos so I can play them on videogular2 if possible. How can I do this?

I have the following settings: ionic info
Ionic:

Ionic CLI : 5.0.1 (C:\Users\thula\AppData\Roaming\npm\node_modules\ionic)
Ionic Framework : @ionic/angular 4.4.2
@angular-devkit/build-angular : 0.13.9
@angular-devkit/schematics : 7.3.9
@angular/cli : 7.3.9
@ionic/angular-toolkit : 1.5.1

Cordova:

Cordova CLI : 9.0.0 (cordova-lib@9.0.1)
Cordova Platforms : android 8.0.0
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 4.0.1, (and 5 other plugins)

Utility:

cordova-res : 0.3.0
native-run : 0.2.2

System:

NodeJS : v10.16.0 (C:\Program Files\nodejs\node.exe)
npm : 6.9.0
OS : Windows 10