[mythtv-users] Hardware for Best TV-Out?

Dan Lanciani ddl5 at danlan.com
Wed Oct 27 23:09:50 UTC 2004

|> |Trouble with that is now your HSYNC's tolerance is
|> |227.5 times more important to get right.
|> That's why I said that this is hard to do after the fact. :)
| 	Yes and no.  Aside from the fact that Modelining up a very precise 
|frequency may or may not result in that frequency from card to card, you 
|will at least know what it is from the modeline and X logs.  Aside from 
|the drift in the dotclock, re-multiplying what was divided by the modeline 
|(say, by 910 for a 14.318 MHz clock) should be a 1:1 operation.  I suppose 
|there would be jitter, etc on that, though.

I just don't know enough about what's going on in the VGA card to guess one
way or the other whether it would be a problem.

| 	What a rip off then!  They're basically the same (unless they'll 
|do progressive, fancy deinterlacing, etc).  480i on component isn't any 
|different temporally... just adding a bit, filtering a bit different, and 
|demoding the chroma.

Nope, no progressive scan conversion.  If you don't buy the "transcoding"
option then only the output type corresponding to the input you are using
is live.  If you buy the option then all the outputs are always live.  I
think the option actually removes some interlock logic...

| 	OK... so you've got a more complicated setup, so I can imagine 
|a problem with non-locked subcarrier.  I'm assuming that the RF modulator 
|is trying to use the subcarrier for something then?  In fact, if it's a 
|BTSC-stereo RF modulator, I think it's a requirement, no?

It is (stereo) but I'm not exactly sure what it is doing.  I don't like
the quality of the MTS encoding at all.  This was a medium expensive (~$600)
unit but it was one of the first ChannelPlus offerings in the range and
even they admit that it isn't great.  (They didn't build the audio encoder
module; they had to buy it to comply with the license.)  This is another
thing on my list to replace, maybe with a Blonder Tongue "professional" unit.
Because the good ones require a channel-specific filter module I'm waiting
for the whole digital/analog debacle to resolve itself.  If all VHF OTA TV
really goes away then I take down my VHF antenna and use that space for my
in-house channels.  But I think that sounds just a bit too easy. :)

| 	Like I said, I haven't tried the TVOUT on most vid cards because 
|the digital end of it (scaling, resampling, etc) sucks so hard, that it's 
|already irrlevant if the NTSC output isn't quite spec.  It's already crap.

I guess that's the price we pay for flexibility.  Back on the ATI EGA Wonder
if you wanted to use the composite out you programmed the timing for NTSC
rates.  There was no scaling or resampling performed by the card.  Now when
people talk about getting a TV to sync to 800x600 modes of an nVidia card
it isn't even clear what they mean.  (Not that the EGA Wonder produced good
looking TV output, mind you.)

|> I never expected a $35 card to work well enough.  That's why I was looking
|> for other solutions. :) I still think DV-out to a Sony DVMC or Miglia codec
|> could be the way go.  It might also solve the other problem I frequently
|> see with TV-Out support: hum bars from some sort of ground differential.
| 	It would appear that $200 is the magic number for something 
|"professional enough" to put out good, standards-compliant signal.

Just to be clear: you aren't saying that there exists something I could
buy for $200 that will do what I want, right?  Because I'd be happy to
spend that money.  Or even twice that money...

				Dan Lanciani
				ddl at danlan.*com

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