I have vps server and i setup ffmpeg successfully. I downloaded 720p hd video. I need only add text on video. And i added successfuly but video quality is very low after adding. I use this command

```
ffmpeg -i a.mp4 -vf "drawtext=fontsize=30:box=1:fontfile=/usr/share/fonts/a.ttf:text='Stack Overflow':x=(w-text_w)/2:y=(h-text_h-line_h)/2" -strict -2 c.mp4

```

I dont know -strict -2 command. i try and ffmpeg error say add -strict -2 then i add. Now i need only add text, not change video quality.