[mythtv-users] pcHDTV with PVR-350 for output

Doug Larrick doug at ties.org
Sat Oct 23 13:39:12 UTC 2004

Dan Lanciani wrote:
> |> Right, I got that.  And I think it is the correct approach since it
> |> preserves maximum information.  However, I somehow had the idea that it
> |> would transcode and scale as necessary near the output.  (In my defense,
> |> there is a lot of code in MythTV proper and a rather large number of
> |> libraries.  It isn't immediately obvious that it doesn't do this. :)
> |
> |If you tell it to transcode, it will.
> How would I tell it to transcode in this situation?
> |It won't be realtime, though.
> What prevents it from being real time?

It's way too compute intensive.  Probably by a factor of at least 2.  It 
would have to decode, resample, and re-encode.  Doing this in software 
is beyond the capabilities of current general-purpose computing hardware.

There's also the small matter that what Myth stores for HDTV is an 
MPEG-TS (transport stream) file, not an MPEG-PS (program stream) as 
expected by the PVR-350.  This is aside from the frame-size limitations 
mentioned by others.  Nothing in MythTV is set up to account for any of 
this at all.

To do what you want to do, you're better off using an nVidia MX-440 or 
FX5200 and using its svideo output, since you *do* have the horsepower 
to decode ATSC-sized frames in realtime.  Then the video card would do 
the scaling (in hardware), and you're good to go. An MX-440 is less than 

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