Despite the mention of gaupol, in your original post, your subject talks about adding options to mplayer, and you illustrate a separate command line use of mplayer. Somehow when I tried to view the PNG file it was too fuzzy/out of focus. I couldn't really see what you were trying to show us. So you could have been trying to use the mplayer command separately.
If your issue is within gaupol, and you are using the gaupol which is a subtitle editor, if you are using version 0.17.1 or a compatible version, then you should be able to go through these menu selections, Edit==>Preferences==>Preview; on the Preview menu, in the Video Player section, the Application selection has a choice of Custom. When you choose that, you can type in your own command to use whatever external command you'd like for preview. I just typed in another mplayer command line. When you move your mouse pointer into the box where you can type the command, you should see a list displayed, of the four gaupol related values which can be used within the external command, such as $MILLISECONDS, etc.
Hope this helps.