Artefact on mp4 convertion to mpg

[cybel]

Summary of the bug:
How to reproduce:

% ffmpeg -i input -target ntsc-dvd -codec:v mpeg2video -vf scale=720x576,interlace -b:v 4000k -codec:a ac3 -b:a 192k -ar 48000 output
ffmpeg version last
built on ...

I downloaded a mp4 video from the web on my computer with good quality.
I converted it with the specified command with FFMPEG.
All did okay.
But when i write it on a DVD, my lector transmited some artefacts on my monitor at every view changement.
Is it possible to convert with quality some mp4 videos to mpg with FFMPEG or did i maked a mistake with the command.
Thanks