doing something wrong in avidemux resizing mp4

I want to join 2 mp4 files with avidemux. One is 640x460; the other 640x360. With the 640x360 mp4 I tried to change its aspect ratio with Video => filter => transform => add border. The window shows the clip will become 640x480, as desired. Then the choice was highlighted; its preview looked good; so OK was pressed. Then the add border was choice highlighted again and close was pressed. The transformation doesn't appear in the 1st frame as in the preview. The mp4 was saved and it was still 640x360.
Win 7; 64 bit; avidemux 2.6.10.

Was the video output set to copy or x264 ?

wasnotwas said:

Was the video output set to copy or x264 ?

It was set to copy

Should be on x264 to add borders - even with filter set, on copy it does just that. This is a recode job.

x264 worked; thanx. However, a click was introduced when the resulting mp4 was played.