My HDTV is SO grainy!

When I watch my blu-rays on my computer, they look beautiful, but when I play them on my TV they look REALLY grainy, distractingly grainy, and it hasn't always been this way, but I've looked through it's settings and reset the settings a few times, and it's still grainy. Any ideas on what to do? It's a cheap POS Dynex DX-L40-10A by the way.

~EDIT~
It's 1080p and so are the Blu-ray's I'm watching, so it's not like it's using a reallllly ****** downscaler or anything.

~EDIT2~
Also, whenever I connect my TV to my Macbook, Mac OS think's it's 720p, but I've looked at both Dynex and the panel manufacturer's sites and they both confirm that it is indeed 1080p, why would it lie about it's native res and is there anyway to fix it?
Edited by marcusj0015 - 1/11/13 at 1:00am

Actually, if we're going to get technical, my Mac is a Retina MAcbook, and has over 5 million pixels.

My info button say's it's running in 1080i which is odd, beucase it does support 1080p, but also I've realized that my EDID is masivly messed up, but I've got Win8 on my Macbook for windowsy things, and it doesn't want to play nicely with the EDID editor apps, do you have any idea how to get my TV to regenerate it's EDID, or any EDID editors that will actually work? there's one called ViewSonic EDID Editor, which seems perfect, but it can't read it becuase of some ActiveX bs. :/

Not to be an *******, but yes, there are TVs that do a lot better job than my Dynex, but I don't really have the money to just run out and buy a new TV. (I'm a college student.)

Yes, I'm connecting it through HDMI and the TV is set to output at 1080p.

I think that grain I was talking about, is actually interlace lines, that makes a lot more sense.

Also, this TV was reported to support 5.1 audio, but it tells the OS that it's only capable of 2 channel audio.
Edited by marcusj0015 - 1/11/13 at 12:27pm