You can screen capture a video file through VLC media player, follow the simple steps below

Taking A Still Screenshot

Use hotkeys to take the screenshot. For Windows, press Ctrl + Alt + S. For Mac, it’s Command + Alt + S.

Or, use the Video menu. Click Video at the top of the screen, and select Snapshot.

Change where your screenshots are saved. If you don’t know where your screenshots are going, or you want to change where they’re saved, click Tools, then Preferences. Click Video on the left. At the Video Snapshots section at the bottom of the screen, you can set the destination for your screenshots.

Streaming Your Desktop

Install VLC.

Open VLC.

Click Media, then Streaming.

Click the Capture Device tab.

Select Desktop as the Capture mode.

Change the fps (optional). If you wish, you can change the frames per second rate. If not, though, leave it on default.

Click Stream.

Make sure the source is your screen. If the dialog box is blank, enter screen://.

Click Next.

Choose were to save your file. Click the Add button on the right side of the screen.

Change the file type (optional). VLC will probably default to MP4. If you want a different file type, click the drop menu and select your choice.

Stream.