[mythtv-users] MediaCenter Plan/Help

Michael T. Dean mtdean at thirdcontact.com
Mon May 30 14:37:09 UTC 2005


Thomas Witzel wrote:

> I'm planning on using MythTV for my media center. I have not purchased 
> anything yet and my investigation/planning is now causing major 
> confusion for me.
>
> This are the facts so far:
>
>  - I'm going to have Comcast digital cable and will most likely get a
>    DCT6412 with it.
>  - I'm going to have a 42" Plasma display (no make picked yet, due to
>    the confusion) I'm looking to get one with 1024x768 resolution.

You do realize that 1024x768 is a 4:3 ratio.  720p is 1280x720.  (Since 
you mention 720p below, I thought I would emphasize this distinction.)

> Now here comes my confusion:
>
> A) In most stores here in the Boston area the picture on the displayed
>    42" panels is outright ratty. They often show DVD's and on most
>    displays every motion of a character causes so strong artefacts
>    that it is unwatchable. Store attendants assured me that this is
>    normal. Why would anyone want to buy this, if that was normal.
>    I was thinking maybe something is wrong with the conversion, but
>    I'm told that there is no such thing as format conversion.

No idea.  I don't have any experience with plasma displays, but I can 
tell you I wouldn't pay what they're asking for a plasma display if the 
quality is as you've seen.

> B) I was planning on connecting the Display by just a single DVI-D
>    cable and have all the components in a cabinet some 18ft away.
>    In the store I was told that the DVI-D cable wouldn't provide
>    good quality (which makes no sense to me), and that I would need
>    a component cable anyway to watch TV stations that are not
>    HD (which also makes no sense to me, however comcast couldn't
>    promise me that I wouldn't need it).
>    Now, if I'm right and a DVI-D is sufficient (my audio will go
>    somewhere else), it seems like none of the home-theatre receivers
>    support DVI-D sources for switching. In every store they want
>    to make me convert to components or even svideo.

Component is analog.  DVI-D is digital.  If your TV is a digital display 
(i.e. as opposed to an analog display with a digital tuner--a high-def 
CRT, for example), DVI-D has the potential to give you a very good 
quality image.  However, A/D and D/A conversions are common enough that 
even a mis-matched signal/display type tend to yield very high quality 
images, too.  However, over long distances, you'll probably get much 
better results with a very high-quality component cable (i.e. one with 
very strict impedance tolerances) connection--digital cuts off at a much 
shorter distance than analog.

Basically, though, with MythTV, everything goes into your Myth box for 
encoding, and therefore, the only connection to your display is from 
your Myth box.  Since the Myth box supports things like de-interlacing 
and post-processing, you can configure it to perform whatever "fixes" 
you feel are necessary for improving your video quality.  Therefore, 
just choose one connection format and configure it to work.  Anyone at a 
store will be clueless about this possibility because, paraphrasing 
something Isaac once said, the "convergence box that's been talked about 
for a few years" is still "mythical" to the rest of the world.

> C) Can MythTV drive a Display with 720p (assuming that will be the
>    native mode of my TV) and have devent looking DVD playback ?
>    Is there anyway to passthrough the DVI-D from the comcast box
>    or to switch between the different DVI sources controlled by
>    MythTV ?

See above.

> D) Im getting confused about the firewire as well. Will it now
>    work for recording, or not.

In theory, yes it works with receivers that support it.

> If the content is 5C encrypted, can
>    the encrypted stream be recorded and later be displayed by my
>    Display (which supports HTCP) ?

No.  The 5C standards state that if the device to which a 5C-enabled 
device is connected does not support 5C, the 5C-enabled device must 
down-res the video to no more than 480p (720x480--i.e. DVD quality).  
Therefore, if your content is protected by the broadcast flag, and your 
receiver supports 5C (i.e. HDCP), when you connect the firewire link to 
a non-HDCP device (i.e. any computer), the maximum resolution you can 
get is 480p.  To store the encrypted stream, the device doing the 
storage must support either D-VHS or CPRM (the 5C technologies for 
storage; HDCP is for transmission) and must store the encrypted stream.

HTH.

Mike


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