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

Daniel Thor Kristjansson danielk at mrl.nyu.edu
Mon Oct 25 13:18:43 UTC 2004


On Sun, 24 Oct 2004, Dan Lanciani wrote:
]Daniel Thor Kristjansson <danielk at mrl.nyu.edu> wrote:
]If "very high" equates to about twice what we have now, it shouldn't be
]long before this is not a problem.  In any case, it would be nice to have
]at least *some* independence...

Very high would be 10 to 20 times the CPUs of today if you wanted to 
encode 1080i. Outputting 640x480 MPEG2 while decoding 1080i should be 
doable in a few years.

]|But don't fret too much about FireWire/DV, a P4/1.8Mhz can cope with DV, 
]Meaning that it can transcode to it from any of the on-disk formats you may
]use in real time or meaning that it can only render it to a display?

It is probably possible to do both now on a fast computer, but it is 
not implemented in MythTV.

]I didn't realize it worked with any FireWire input; is this documented
]somewhere?  (I don't care about encrypted streams; I just want to move
]video among my internal devices.)

Not yet, but it is possible, and there is some interest in doing it. 
Macintosh software for doing it already exists.

]|We can get fast-play working with HDTV, but it's not yet high priority.
]|It's mostly a ffmpeg w/MythTV issue.
]Ah, I didn't realize that this was not supposed to work.  Does any kind
]of fast forward functionality work?  Rewind?

Skip works. And fast forward works on very powerful processors. But we 
can make it easier on the processor, it just requires some tweaking. But 
first we need to get regular play working better.

]|I don't think anyone is working on 
]|DV out, DV looks pretty crappy compared to what you can do with a good 
]|TV-out setting
]Sorry, but I really find this a bit hard to believe. :(  And even if it
]doesn't look good it is the accepted way to interconnect with other non-
]display devices.

Yes, it is an accepted interconnect so it belongs in MythTV. But I 
don't think antone is working on it. 

]|(For instance, I can get my plain old TV to sync to a 
]|800x600 signal from the FX5200.)
]I'm not sure what this means.  Are you actually generating 600 (300 
]interlaced) scan lines?  If so that's not real NTSC anymore.  Maybe you 

Yes, it works with my specific TV. It should actually work with most TVs 
with composite input, but I've never published my modeline because it 
can destroy some older TV's.

]can get a specific TV so sync to it, but it won't work as a general 
]video source.  And this is my main gripe with the TV-out support on 
]every video card I've ever tried.  You can tweak this and that to get 
]it to almost look right on a particular TV, but the signal is so far 
]out of spec that it's useless for anything else.

Hmmm, well safe modeline adjustment could be added to MythTV. Right now 
MythTV setup is admitedly a pain. There are some standalone programs out 
there to generate modelines. One used to actually come with both RedHat 
and Mandrake, but has been dumped because most computer monitors these 
days tell X11 how to drive the monitor. But TV's don't and setting them 
up is very much like setting up XFree86 was like 10 years ago.

]I haven't even noticed the ringing yet.  It is completely overshadowed by
]the horrible motion artifacts.  Even as someone moves their hand across the
]screen you can see lots of black scan line "checks" around the motion.  I
]know it isn't a problem with the source stream because my ancient DTC-100
]renders a perfect NTSC representation of the same program.  I don't know if
]it is an MPEG decoding issue or an NTSC encoding problem, but it (IMHO) makes
]the output useless.  (See my previous message about the FX5200.)

Are you using XvMC? Try XV if you are. This sounds like a bug. Does 
it look good in mplayer? Does it look good on your monitor?
If it looks good on your monitor, and not on TV out, you may have a 
broken nvidia video card.

]I'm going to keep playing for a while, but I get the feeling that what I
]want (ATSC source; real NTSC out) is not possible with the current selection
]of hardware and software. :(

It is not one of the setups we test, but it should work if the output is 
an XV surface.

-- Daniel


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