Memorex doesn't make their own DVD players, they re-badge
other companies DVD players, the net result being that
all of their players use different remote control codesets.
Therefore, in order for anyone here to have any chance
of finding you the right code, they would need to know
the exact model number of your Memorex DVD player.

Furthermore, Comcast uses more than one vendor for their
remote controls, so we would also need to know the model
number of your Comcast remote. Here is a page that displays
many of the remotes tha Comcast uses, if you see your
remote there please tell us the name of it, and please
quote it exactly as there are several remotes with similar
names.

[Link: comcast.com]