@bazza, I tried your options on this image:
and also had no quality deteriorations.
But on this image:
I get bad video quality even with your settings.
Could you please also convert the last image with your settings to see how it goes?
@bazza, I tried your options on this image:
But on this image:
MP4 requires big capacity of CPU/GPU for the compression maybe your computer was not the sufficiently good.
Another option is that it was by that you do not use wonderful GNU/linux
try with MPEG