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bleudyno · Mar 1, 2004, 07:44 PM

Hey guys, I have a Mitsubishi 55" widescreen tv with dvi input on the back. I hooked it up to my PowerMac G4 but all i get is a black screen. When i turn it on, the tv shows the grey screen with the little macintosh smiley face but then after that, the screen just turns black. Does anyone know what could be the matter and how i can get it work on my tv? DO i have to set any settings? Thanks

David

Eriamjh · Mar 1, 2004, 07:51 PM

You probably need to "pre-set" the resolution of the TV on the Mac on the original monitor...

The TV is not compatible with the Video card, or the Mac doesn't know what to do with it.

Detrius · Mar 1, 2004, 08:09 PM

Hook your existing monitor up to your Mac while the TV is hooked up and see what you get. In fact, boot the Mac up with your existing monitor and THEN hook up the TV to the DVI jack. OS X can handle it... hot-swap monitors. (that's what the 'detect displays' button is for).

bleudyno · Mar 1, 2004, 09:56 PM

Originally posted by Detrius:
Hook your existing monitor up to your Mac while the TV is hooked up and see what you get. In fact, boot the Mac up with your existing monitor and THEN hook up the TV to the DVI jack. OS X can handle it... hot-swap monitors. (that's what the 'detect displays' button is for).

I tried that and when i do that, the screen on my lcd monitor freezes while the tv still shows a blank screen. How do i know if my video card can handle it? What other settings so i need to fool around wiht?

kupan787 · Mar 2, 2004, 02:11 AM

Originally posted by bleudyno:
I tried that and when i do that, the screen on my lcd monitor freezes while the tv still shows a blank screen. How do i know if my video card can handle it? What other settings so i need to fool around wiht?

Nvidia cards can't do interlaced output. Some ATi cards can (the newer ones I know, not sure which older ones). ATi has info on their website some place telling which cards work with HDTVs and which don't. And yes, your HDTV is interlaced. HDTVs all have a native resolution, they can't switch between multiple like a normal computer monitor. 99% of RPTVs are 1080i (I think most LCD and Plasmas are 720p). So that means any and all signals are upconverted to that rate.

I learned all of this after I tried doing the same thing with a GeForce 3.

Big Mac · Mar 2, 2004, 02:12 AM

I would try turning down the resolution.

bleudyno · Mar 2, 2004, 11:21 AM

Originally posted by kupan787:
Nvidia cards can't do interlaced output. Some ATi cards can (the newer ones I know, not sure which older ones). ATi has info on their website some place telling which cards work with HDTVs and which don't. And yes, your HDTV is interlaced. HDTVs all have a native resolution, they can't switch between multiple like a normal computer monitor. 99% of RPTVs are 1080i (I think most LCD and Plasmas are 720p). So that means any and all signals are upconverted to that rate.

I learned all of this after I tried doing the same thing with a GeForce 3.

Okay i turned down the resolution and it still didn't work. I do think i have a geforce card so are you saying that geforces can't work with HDTVs?

kupan787 · Mar 2, 2004, 11:54 AM

Originally posted by bleudyno:
Okay i turned down the resolution and it still didn't work. I do think i have a geforce card so are you saying that geforces can't work with HDTVs?

Correct. Nvidia cards can't output in interlaced format. It doesn't matter what resolution you set your Mac to, the card just can't do it. I know there are ATI cards out there that can (not sure which, but ATi has a list on their site some place).

kenty · Mar 2, 2004, 03:49 PM

Originally posted by kupan787:
And yes, your HDTV is interlaced.

I thought HDTV's could do 720p, (720 lines progressive) ?

If the High Definition has a VGA port, then it has to do progressive because VGA is a progressive format.

kupan787 · Mar 2, 2004, 10:26 PM

Originally posted by kenty:
I thought HDTV's could do 720p, (720 lines progressive) ?

No. HDTVs are not like computer monitors. An HDTV can't do multiple resolutions. Therfore it has 1 native resolution. On almost every RPTV (rear projection tv) this native resolution is 1080i. What this means is that all other SD and HD formats are "upconverted". So if a 720p signal is inputed, it is upconverted to 1080i to be displayued.

If the High Definition has a VGA port, then it has to do progressive because VGA is a progressive format.

Not quite. The port is an RGB port, not VGA (I don't know if that is 100% the same, but I am guessing not as it is labled as RGB not VGA). My parents TV has this RGB port on it, and it is 1080i native.

Big Mac · Mar 3, 2004, 04:55 AM

Learned a lot from this thread... Oh, that's really interesting that HDTVs have RGB inputs - I haven't heard of RGB since my 12" Apple monitor, the one that came with my LC! I'm not sure I understand why progressive output won't work, according to what has been posted here. If everything gets "upconverted," why should there by any problem?

ginoledesma · Mar 3, 2004, 06:49 AM

ATI Cards that don't natively support HDTV can be used with ATI's HDTV Component Video Adapter. Unfortunately, the software that comes with the adapter is only for Windows.

Detrius · Mar 5, 2004, 09:05 AM

Originally posted by kupan787:
No. HDTVs are not like computer monitors. An HDTV can't do multiple resolutions. Therfore it has 1 native resolution. On almost every RPTV (rear projection tv) this native resolution is 1080i. What this means is that all other SD and HD formats are "upconverted". So if a 720p signal is inputed, it is upconverted to 1080i to be displayued.

But if the TV itself is a 720p, it is progressive scan. Like you said: *almost every*.

kupan787 · Mar 5, 2004, 03:38 PM

Originally posted by Big Mac:
Learned a lot from this thread... Oh, that's really interesting that HDTVs have RGB inputs - I haven't heard of RGB since my 12" Apple monitor, the one that came with my LC! I'm not sure I understand why progressive output won't work, according to what has been posted here. If everything gets "upconverted," why should there by any problem?

Because everything gets upconverted to an interlaced signal, which the Nivida cards can't do

Originally posted by ginoledesma:
ATI Cards that don't natively support HDTV can be used with ATI's HDTV Component Video Adapter. Unfortunately, the software that comes with the adapter is only for Windows.

Ya, that is what I was refering to (they have a list some place tellign which cards do and dont work). Do you knwo if you need the software?

Originally posted by Detrius:
But if the TV itself is a 720p, it is progressive scan. Like you said: *almost every*.

Correct. But his TV is not 720p native. I don't personally know of any RPTV that are 720p native, but I am sure there is one or two out there, that is why I said almost every. I know that most LCD and Plasma TVs are 720p native, so an nivida card would probably work ok with that setup.

On a side note, some new (expensive) RPTVs are coming out as 1080p native (1080p was part of the original HDTV format, but hasn't been done do to cost of parts I believe).

MaxPower2k3 · Mar 5, 2004, 04:05 PM

it is true that nearly every RPTV natively displays 1080i. However, all but the cheapest TVs will upconvert a 720p signal to 1080i. While not as good as supplying a native resolution picture, you could set your computer to 1280x720 resolution at 60Hz and see if your TV will take that and upconvert it.

As for TVs having RGB ports, this is not quite true. VGA is RGB (plus a couple of other signals) but what most people call the RGB input on the TV (most likely because the plugs are red, green, and blue) is actually a component video input, which has Y, Pr, and Pb signals. true RGB inputs (which usually use BNC plugs) are often only found on higher-end televisions, or as a VGA port (most of the time used solely for a computer connection, and restricted to computer resolutions such as 1024x768 -- not ideal for a HTPC)

i'm almost positive the above information is correct; if i made a mistake, don't kill me

kupan787 · 08:13 PM

Originally posted by MaxPower2k3:
it is true that nearly every RPTV natively displays 1080i. However, all but the cheapest TVs will upconvert a 720p signal to 1080i. While not as good as supplying a native resolution picture, you could set your computer to 1280x720 resolution at 60Hz and see if your TV will take that and upconvert it.

Now that I think about it, that is a good point. All I know is that when I tried it with my GeForce 3 and my HDTV, I had no luck. Maybe my card doesn't have enough VRAM? The original poster didn't have much luck either, so I am guessing that there is a tie between the nvidia/interlace thing and these TVs.

As for TVs having RGB ports, this is not quite true. VGA is RGB (plus a couple of other signals) but what most people call the RGB input on the TV (most likely because the plugs are red, green, and blue) is actually a component video input, which has Y, Pr, and Pb signals. true RGB inputs (which usually use BNC plugs) are often only found on higher-end televisions, or as a VGA port (most of the time used solely for a computer connection, and restricted to computer resolutions such as 1024x768 -- not ideal for a HTPC)

i'm almost positive the above information is correct; if i made a mistake, don't kill me

Ya, when I said RGB port I meant an RGB port. My parents HDTV (a Pioneer elite) has an RGB port on it (it was before DVI was coming out on HDTVs). I don't know of many devices that take advantage of it (their HD set-top box uses component inputs), as it seems everything uses DVI today. Funny thing is that the RGB port on the HDTV says not compatible with a computer.