If the aspect ratio of your DVDs is incorrect, press the ASP. RATIO button of your Zappiti RC.

Some DVDs may however be displayed in an incorrect ratio, despite the fact that you use the ratio button on the remote control. Indeed, the image may be very slightly stretched. The reason is that DVDs use non-square pixels. Historically, analog video used lines generated by scanning (interlaced lines) rather than pixels like today. 

The correspondence in non-square pixels of a DVD resolution was 720x576 for PAL DVDs and 720x480 for NTSC. The correspondence expressed in square pixels is 768x576 for PAL DVDs and 768x480 for NTSC DVDs. 

The Realtek chip used in Zappiti players is unfortunately not able to dynamically transform non-square pixels into square pixels as is the case with Blu-ray players. If you are sensitive to image quality and If you want to display your DVDs in perfect aspect ratio, you can re-encode your DVD files to MKV using FFmpegYag (or other software) by changing the resolution 720x576 to 768x576 for PAL. For NTSC 16:9 DVDs, the 720x480 resolution should be changed to 768x480.