Resize source video to DVD video format: Avidemux Menu -> Auto -> dvd
select in auto DVD () popup window for
anamorphic
- Source Aspect Ratio: [1:1]
- Destination Aspect Ratio: [16:9]
end result 720p on YouTube -> Avidemux Menu: Auto: DVD 576 16:9 anamorphic (https://www.youtube.com/watch?v=oWLBiBsFFmA)
letterbox
- Source Aspect Ratio: [1:1]
- Destination Aspect Ratio: [4:3]
end result 720p on YouTube -> Avidemux Menu: Auto: DVD 576i 4:3 Letterbox (https://www.youtube.com/watch?v=6ECSx-cBuw0)