[mythtv-users] HDTV and AMD

Brandon Beattie bbeattie-maillist at linkexplorer.com
Wed Apr 21 12:21:24 EDT 2004

Hi Vince,

 I'm the one who has been making the hardware recommendations for the
pcHDTV card and Myth.  The system doing the recording (backend) does not
have to be much of anything.  I actually was set to us a p3 450 with all
3 cards, but when I decided to do transcoding on the hdtv files to save
space, this is what changed my mind.  If you never plan on transcoding,
anything over 800mhz I'd say is fine (cpu usage for streaming out up to
45Mb/s, disk accessing, system overhead, etc).  

You can have capture cards in any system.  I know of some people who run
a backend with normal atsc cards and the frontend with a pcHDTV card.
It works both ways too.  

The only concern for the CPU's is that code has not been optimized as
well as it could be.  Watching hdtv, (1080i which is the most CPU
intensive) can work on a 1.7ghz when proper de-interlacing and video
frame handling is done.  Anyone who watches HDTV right now will notice
that the X server takes about 40-50% of the CPU just to display the
video stream. Decoding in Myth works about as well as it should
(software hdtv decoding, not related to displaying or de-interlacing).

The bottom line is X needs to be reworked a bit to improve video quality
for video.  X has always had a major flaw in this area (Such as no
vblank support and no way to know if/when a video frame is actually
displayed on the card.. such features exist in Windows but not X yet.
The next concern is writing better de-interlacing algorithms for Myth.
The current "fix" is to throw more horsepower/CPU at X and Myth to help
compensate for the design issues.  Hopefully this will all be worked out
in the new X server (Which they have been addressing recently) and when
someone gets time to write some more de-interlacing algorithms for


On Wed, Apr 21, 2004 at 11:20:10AM -0400, Vincent K. Britton wrote:
> I know Mr. Wilson has told me that the "recommendation for optimal HD
> playback with MythTV is a 3.0GHz HT P4" but is there anything from the
> AMD family of processors that has Proven itself capable of decoding HDTV
> for a front end.
> That being said am I correct that the computer with a pcHDTV capture
> card can be the backend and doesn't have to be "beefy" it is just the
> front end machine.  
> Can you have capture cards in other machines but still have one master
> backend server?
> Thanks to all for helping me with my endless questions.  I am trying to
> find the answers to these questions online but am not having any luck.
> Sincerely,
> Vince

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