Video VideoClipImporter programmatically

Hello,

About this thread https://forum.unity.com/threads/settings-for-importing-a-video-with-an-alpha-channel.457657/ I need to download from url a webm file and play it on Android.
But this mean I need to use the VideoClipImporter to set KeepAlpha to true and this is not possible beacuse the webm file isn't in Unity from Editor.
It's possible to use programmatically the VideoClipImporter? If yes, someone have a example code?
Thanks