[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
$50.
-Doug
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