How can I lock the keyboard and mouse when playing video

Solution 1:

Try xtrlock,

xtrlock locks the X server till the user enters their password at the keyboard.

   While  xtrlock  is  running, the mouse and keyboard are grabbed and the
   mouse cursor becomes a padlock.  Output displayed by  X  programs,  and
   windows  put  up  by new X clients, continue to be visible, and any new
   output is displayed normally.

   The mouse and keyboard are returned when the user types their password,
   followed  by Enter or Newline.  If an incorrect password is entered the
   bell is sounded.  Pressing Backspace or Delete erases one character  of
   a  password  partially  typed; pressing Escape or Clear clears anything
   that has been entered.

   If too many attempts are made in too short a  time  further  keystrokes
   generate bells and are otherwise ignored until a timeout has expired.

   The  X  server  screen saver continues to operate normally; if it comes
   into operation the display may  be  restored  by  the  usual  means  of
   touching a key (Shift, for example) or the mouse.

install it using

sudo apt-get install xtrlock

Open terminal run xtrlock to lock the Keyboard and mouse inputs .

Caution , Enter your Active user Password to unlock it and press enter.