I never used VLC player before for YouTube Videos. But I know how to change the playback speed in Browser.
When a YouTube video is playing in the browser, press D or Shift + D until you hear Main Landmark Clickable Complementary Landmark.
Then press tab until NVDA says Seek Slider and says the time of the video which is playing. For example
Seek slider slider 3 minutes 14 seconds of 12 minutes 57 seconds
Now press Shift + > to increase the playback speed and Shift + < to decrease the playback speed.
And arrow keys to skip the video forward and backward.
Pressing the Escape key will move the NVDA Navigation controls out of the Seek slider.
Reading this will confuse you a lot. So, do the above steps one by one while reading.
Or an alternate method:
Note: The first method is the easiest one.
When a video is playing, press D or Shift + D until NVDA says Main LandMark Clickable Complementry Landmark.
Then press the B key until you hear
Settings Menu Button Submenu Settings
Now press Space bar key or Enter. A menu will open.
Press Down arrow key or Up arrow key to navigate the menu until you hear
Playback speed Normal submenu 3 of 5
Now press Right arrow key to open the menu and press Up or Down arrow keys to select the desired playback speed and press Enter key. This will change the video playback speed.
After changing the playback speed press Escape key to close the settings menu.
Hope you will understand. (Because I am not fluent in English).
If you have any questions, feel free to reply me (your brother). Thank you sir.