problem - appearance of the edited video

[minegroasprilla]

When I cut a scene of this video (output format: mp4 muxer): http://www.mediafire.com/file/yw2up1dvvpudl0b/PRUUUUU.mkv/file
I get a shrunken image on the sides (similar to 4:3 format), like these pics:
https://i.imgur.com/EflhYux.jpg
https://i.imgur.com/wiF5NCM.jpg

I have had that problem with some videos. Any fix?.

[eumagga0x2a]

If a source video is anamorphic (i.e. its pixel are not square), you must force the matching display aspect ratio in the settings of the muxer so that this information gets stored in the container metadata. Please note that Avidemux displays all videos with square pixel, but most video players will show them with the correct aspect ratio.

[eumagga0x2a]

By the way, the MKV specifies wrong width 1430, the right one (1440) is set in the video stream. You should force the 16:9 display aspect ratio in the Mp4 muxer.

[minegroasprilla]

You should force the 16:9 display aspect ratio in the Mp4 muxer.

How can I do that?.  I'm not very skilled with Avidemux.

[eumagga0x2a]

Press the button "Configure" below the output format name, in this case "MP4 Muxer". Check the checkbox "Force aspect ratio" in the appearing dialog and ensure that "Aspect Ratio (DAR)" is set to "16:9" (which is the default value).