When I use 160x120 in IR monitor my image looks distorted, why?

160x120 image size details is reflected as 160x160.

You need to change a setting in ffdshow to correct this behavior

Right click on the ffdshow icon in the right corner from the menu choose "ffdshow video decoder"

On the left menu scroll down to Output and click on it.

Make sure "Allow output format changes during playback" is not checked then click OK.

Restart IR monitor and your image should been corrected as below.