It turns out that I just needed to trick the TV into thinking it was the DivX codec when it is really the xvid codec, by changing the video tag (or FourCC to DIVX) using -tag:v DIVX:

avconv -i input.mp4 -c:v libxvid -c:a libmp3lame -b 700k -tag:v DIVX output.avi

https://askubuntu.com/questions/262631/how-can-i-convert-video-to-divx4-to-play-on-my-kogan-tv