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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Mon Aug 13, 2018 8:01 am    Post subject: RGB resolution Reply with quote


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Hi,

having my G90 up (in the real sense of the word) and running, I'm wondering how I could actually use the resultions mentioned in the specs (2500x2000 pixels). I have all these nice Mac Desktops and screens with thousands of pixels of resolution. How can I bring this on the G90 (or any other analoge PJ)?

Currently I'm converting the desktop to VGA and send it to my scaler. But although VGA, in theory, is not limited to a given resolution, all VGA convertes seem limited to 1600x1200 - and even this does not seem to work. All the VGA-converters I tried refused to offer this resolution when connected to the HDMI-port of my Mac-Mini.

The scaler also does not offer more than 1600x1200, or 1080p (an Extron model).

So my questions are:

- are there any HDMI/Thunderbolt -> VGA converters that are capable of doing (much) more than 1600x1200?

- what scalers are capable of going beyond 1600x1200 / 1080p on the RGB output?

cheers
Martin
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wanderer



Joined: 11 Jan 2015
Posts: 30



PostLink    Posted: Mon Aug 13, 2018 3:30 pm    Post subject: Reply with quote

The digital 1200P60 HDMI\DVI to VGA conversion limits you are seeing are likely tied to that being single link DVI. Maximum bandwidth on single link DVI is about 165Mhz, so you'd need a dual link DVI > VGA converter if you wanted to run something higher like 2500x2000, etc.

Analog VGA displays can only display resolution with great clarity up to a certain Mhz point. You might get a great clear image at 160Mhz, then things start getting softer as you ramp up the Mhz frequency. A PC graphics card with VGA output can display over 200Mhz easily, but is that really a full bandwidth signal at the proper voltage (at 200Mhz) and is the video display device able to take that 200Mhz signal and properly resolve and display it?

A 2500x2000 signal at 60P with CVT reduced blanking for a digital display is about a 335Mhz dual link DVI signal, with VGA timings that are more friendly for CRT with some decent porches it's more like 437Mhz for that same signal. A normal G90 wouldn't be able to handle a signal like that.

I don't think I've ever seen a dual link DVI to VGA converter, but that doesn't mean they don't exist!
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Tim in Phoenix



Joined: 21 Oct 2006
Posts: 4083
Location: Phoenix


PostLink    Posted: Mon Aug 13, 2018 5:05 pm    Post subject: Reply with quote

Right

Don't confuse theoretical/marketing dept. specmanship with actual possible performance!
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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Tue Aug 14, 2018 12:01 pm    Post subject: Reply with quote

wanderer wrote:
The digital 1200P60 HDMI\DVI to VGA conversion limits you are seeing are likely tied to that being single link DVI. Maximum bandwidth on single link DVI is about 165Mhz...


Thanks for your insights.

Oh well... according to specs the G90 has 135MHz Bandwitch. Indeed, thats OK for 1600x1200 at 50 or 60Hz. I really wonder how the Sony marketing people can come up with a 5 Megapixel resolution. At 50Hz interlaced, maybe.

When I'm in 1080p mode and the scaler puts on a test-image with "alternating pixels", I noticed the width of each "pixel" is wider than my spot size can be. Perhaps 2500 pixel is the optical resolution? With a maximum horizontal frequency of 150kHz it should be capable of painting 3000(!) lines at 50Hz (or 2500 with 60Hz).

What are the limiting factors in the Bandwith? The sginal paths, the video amps, or the picture tube itself?

cheers
Martin
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kal
Forum Administrator


Joined: 06 Mar 2006
Posts: 15475
Location: Ottawa, Canada

TV/Projector: JVC DLA-RS56


PostLink    Posted: Tue Aug 14, 2018 1:56 pm    Post subject: Reply with quote

While a CRT projector may be able accept a specific signal, it may not be able to fully resolve the information on screen without overlapping of scan lines resulting in a softening of the picture. Manufacturer resolution specifications do not necessarily reflect real world resolving capability, especially if the light output is pushed up and the beam spot size gets larger/maybe blooms a bit (doesn't matter how good the e-focus is, the higher the light output the beam will get a bit fatter).

More info in the bottom of the page here: http://www.curtpalme.com/Projector_Rankings.shtm

For what it's worth, I wouldn't bother pushing this (or any CRT projector for that matter) much beyond 1080p (1920x1080). You mention wanting to use it for a computer desktop - it would not be that clear at higher resolutions.

Kal

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gjaky



Joined: 05 Jun 2010
Posts: 2570
Location: Budapest, Hungary


PostLink    Posted: Tue Aug 14, 2018 7:21 pm    Post subject: Reply with quote

Apfelmousse wrote:

What are the limiting factors in the Bandwith? The sginal paths, the video amps, or the picture tube itself?


When dealing with bandwidth the very first thing one needs to do is distinguish the bandwidth (of the CRT projector) and the pixel clock of a resolution. They fall in similar range often, and are somewhat related but they are not the same!

Checking the projector specifications are of little help too, because the given bandwidth numbers are rarely accurate. My favourite example is comparing the bandwidth of a 7" NEC 6PG xtra (80MHz) and the Barco 909 (180MHz), The 6PG xtra can do the bandwidth of 1080P 60Hz very well, while the 909 does not, yet it has 100MHz more bandwidth on paper...

The pixel clock is twice the frequency of the highest repetition frequency possible of a given resolution, however note this repetition rate is meant in square waves, ie. the bandwidth of a faithfull 10MHz square wave signal is usualy much more than 10MHz.

CRT bandwidth supposed to indicate the point where the sine output of the amplifier falls -3dB below the reference point.

In practice one can be happy if the CRT amplifier display the square-wave pixel as a half sine of about the same amplitude, this gives some ease on the bandwidth requirements.

Every stage in a high frequency path (like the video amplifier) have a bandwidth limiting nature, let it be a cable a very good amplifier.
Historically the CRT amplifier is the bottleneck in the signal path (and the cause for this of course the CRT itself), the G90 uses CRT amplifier IC-s those are specified at 150MHz bandwidth, but as I said it is also matters how "long" or "difficult" is the preamplifier stage, and this is where both the G90 and the Barco 909 fails. These flagship models must had fancy video features like menu adjustable gamma correction, and so on, and these features inevitably eat away some (considerable) bandwidth.

By the way my observation on the lack of bandwidth is not the loss of sharpness in the picture but rather inaccurate colour tones, and interestingly this is rarelynoticeablea problem when trying to read a text.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Wed Aug 15, 2018 4:22 pm    Post subject: Reply with quote

Looking at the PJ-comparison table, my old 808 graphics ist rated 1600x1200 pixels, what the unit was definitly capable of. I used it myself...

In the same table are these "montrous" resolutions for the Barco 909 or the G90. I reckon the numbers come from the manufacturer's datasheet. But why have they been serious for an 808 and "exaggerated" for a 909 / G90?

cheers
Martin
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kal
Forum Administrator


Joined: 06 Mar 2006
Posts: 15475
Location: Ottawa, Canada

TV/Projector: JVC DLA-RS56


PostLink    Posted: Wed Aug 15, 2018 6:51 pm    Post subject: Reply with quote

While it depends on how fussy you are, I wouldn't say that an 808 can "seriously" resolve 1600x1200. It would be soft / overlapping. Even 1080p is soft/overlapping on an 808. Similar to 2500x2000 on a G90/909.

In my humble opinion of course - my 2 cents.

Kal

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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Wed Aug 15, 2018 7:40 pm    Post subject: Reply with quote

kal wrote:
While it depends on how fussy you are...

Perhaps not that fussy... but at least the menu bar and all the small text has been very readable.

I noticed the 808 was running hotter on 1600x1200 compared to 1080p.

cheers
Martin
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gjaky



Joined: 05 Jun 2010
Posts: 2570
Location: Budapest, Hungary


PostLink    Posted: Thu Aug 16, 2018 6:48 am    Post subject: Reply with quote

IMHO 1600x1200 (or 1600x900) is indeed a sweetspot for 8" machines. On 9" machines the perfotmance gap is about 10% in terms of resolution, and even less between old and new generation 9" models (1292 vs. G90) but the price difference was much more than that, therefore they had to exaggerate the specs.

As for heating, the power consumption of the projector raises with the scan frequency, this applies to every model.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Sat Aug 18, 2018 6:58 pm    Post subject: Reply with quote

Agreed. So with 10% more, 1600 becomes roughly 1800. Probably OK for 1920x1080p.

Pity all those 1080p resolutions, be it with 1080 lines or 1200, are not 4:3, which would be a better ratio for me (and for the beamer).

Ratio-Wise, with 1920 pixel horizontally, I should have 1440 lines. Is there any VGA device or scaler that can handle this type of resolution? They all seem to go 16:9 at higher resolutions.

cheers
Martin
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gjaky



Joined: 05 Jun 2010
Posts: 2570
Location: Budapest, Hungary


PostLink    Posted: Sat Aug 18, 2018 7:55 pm    Post subject: Reply with quote

HDMI 1.3 version support 2560x1440 at 60Hz maximum, so any PC videocard of that kind should support that as well.
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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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The MOD: VNB-DB
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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Sun Aug 19, 2018 4:36 am    Post subject: Reply with quote

gjaky wrote:
HDMI 1.3 version support 2560x1440 at 60Hz maximum...

Do you know of a converter capable of making RGB out of that?

All those I saw were limited to 1600x1200 or 1920x1080p.

cheers
Martin
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gjaky



Joined: 05 Jun 2010
Posts: 2570
Location: Budapest, Hungary


PostLink    Posted: Sun Aug 19, 2018 11:17 am    Post subject: Reply with quote

Any videocard from the past 10 years with a VGA output is the best bet. VGA was allowed to go 2048x1536 75Hz. None of the after market HDMI-VGA converters were designed to go beyond 1080P.
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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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The MOD: VNB-DB
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Apfelmousse



Joined: 26 Apr 2014
Posts: 65
Location: Germany


PostLink    Posted: Sun Aug 19, 2018 11:50 am    Post subject: Reply with quote

gjaky wrote:
Any videocard from the past 10 years with a VGA output....

Pity... cannot remember having had a Mac with a VGA video card. Mac Minis do have Thunderbolt ports that can be converted left or right or wherever, I find it a bit mind-wobbling.

This loops back to my initial question: is there a possibility to convert Thunderbolt to VGA with, lets say, 1920 x 1440 pixel resolution?

I asked that question at our local Mac dealer... they all turned eyes and had to think of an expert who, of course, was not in the shop that day.

cheers
Martin
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wanderer



Joined: 11 Jan 2015
Posts: 30



PostLink    Posted: Sun Aug 19, 2018 4:14 pm    Post subject: Reply with quote

To answer your question about 1920 x 1440 coming from digital to analog, the timings out of most DVI>RGB converters will be whatever goes in comes out. We're talking digital in and that means CVT reduced blanking times so....
- 1920 x 1440 @ 144Hz = 462Mhz pixel clock. That's on my PC monitor now, so that won't work on CRT.
- 1920 x 1440 @ 60Hz = 184.8Mhz pixel clock. That's above single channel DVI limits so that won't likely work unless a dual channel DVI>RGB converter exists.
- 1920 x 1440 @ 50Hz = 153.3Mhz pixel clock. That would likely work OK!

Most of the standard cheap converters won't adjust the porches though, so you'll run straight into issues with width on a CRT as the front\back porches aren't enough to display the image properly width wise. To adjust the timings you'd need a box that can sample the image and add porch timings to it. Not sure if the Moome can do that, the TVOne and the Radiance boxes should be able to.

Even taking that 50hz CVT pixel clock above at 153Mhz and changing that to GTF or other proper CRT timings would take it to 192 Mhz which is getting up there VGA frequency wise.
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gjaky



Joined: 05 Jun 2010
Posts: 2570
Location: Budapest, Hungary


PostLink    Posted: Tue Aug 21, 2018 10:28 am    Post subject: Reply with quote

If you use a computer as a source adjusting the display timings should be no problem.
On E-bay, there is (was?) white HDMI-VGA converter around $20 or so, which claimed to be support only up to 165MHz pixel clock, but I had success runing it well beyond 200MHz, for this you'd need some mods to be done to it, but nothing serious.
But I don't know if it supports 1920x1440 at all as I've only tested with 1920x1080 and higher refresh rates.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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