Hdmi inputs where are they

I just purchased the Magnavox dvd-r recorder with a 1 terabyte Hard drive from walmart.com.
Magnavox MDR557H/F7 1TB Hard Drive/DVD Recorder with Digital Tuner
My problem is why is there always a hdmi out but never a hdmi in on any of these media units?
On my Cable box I have only 1 hdmi out, 1 S Video out and 1 RCA Composite out.
The HDMI out goes to my HDTV and the picture is great.

Now to record from the same cable box to my Magnavox recorder,
I now only have 1 RCA Composite out or 1 S video out left.
So I choose S video out to record to the Magnavox,
but when I watch what I recorded the picture is terrible.

I guess what I'm trying to say: if you have low quality video coming in to your recorder through S video
then it makes sense you will have the same low quality coming out.
My question Is to you guys is it possible to build a media center
that has a HDMI input so I could record in high definition and a HDMI output to go to my HDTV?

Now I know cable companies make dvd recorders with this capability but If you ever decide to get rid of it you lose all you recorded.
Any advice would be very much appreciated.
 
On my Cable box I have only 1 hdmi out, 1 S Video out and 1 RCA Composite out.
The HDMI out goes to my HDTV and the picture is great.
that's correct.

Take for example, a DVR is inline with the service provide which allows the Recording. Once recorded, it's nice to get the media displayed on an HDTV - - hence HDMI-out.

I have VHS, DVD and daisy-chain them --> HDTV so that the service is feed thru the chain.
Code:
(cable) -- vhs -- dvd -- hdtv
            |             |
            +-------------+
If the VHS is off, the lower path is selected ON THE TV
otherwise, the TV is selected to AV inputs.

The other way to see the layout is
Code:
TV inputs:   (cable) ------ hdtv  select TV:cable input
AV inputs:   av-devices --- hdtv  select TV:av inputs

To record, there needs to be a connection from (cable)-->av unit

yes, S-Video stinks, use the RCA Composite out from the cable->av
 
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