CurtPalme.com Home Theater Forum

[Revox]

Hi, after all what i red i should start to mod my M 8500 electronical.
Before i start had to think about me source, its my PC.
As i know, most graphic Cards are realy cheap produced Cards and as DVI I is the new stardard now, nobody tests the analogue Quality of the output signal.

I got a Radeon X1800Xtx and on my Iyama CRT monitor i can see that the pixel lines are fluctuating a little bit to the left and right (i think it is 1/2 pixel). Ok, my CRT works at 110khz but the same effect will happen to my M 8500.
I cannot beleve that a Hd-fury is much better than a good graphic card.
Depending on the money i got as a student, its not possible to buy a DVI input card for my M.

Do anyone made a workaround with testing graphic cards?

[Mark_A_W]

I have an ATi HD2600XT and the analogue output is superb. I compared it to a HD-Fury on a 24" CRT, and we couldn't tell the difference (except HDMI messes with the black level).

The weak link is the projector, not the graphics card.

[WanMan]

Mark, you are saying that the HDMI on your card messes with the black levels, right? I do not wish to misinterpret you in that HDMI messes with black levels as a global HDMI statement.

[Mark_A_W]

On a PC, HDMI messes with black level. Full stop.


Technically, it messes with everything. HDMI transmits 16-235. Video is 16-235. But a PC is 0-255.
So, if you use video acceleration they expand the video 16-235 to 0-255, to match black levels, then compress the lot down to 16-235 again for transmission over HDMI. These are not lossless conversions.


Or if you don't use video acceleration, and leave your levels alone, you get your 16-235 squished FURTHER during the compression for HDMI.


It's not a problem with HDMI per se, but a problem with the PC implementation of it.

I hope somebody can prove me wrong.

[Revox]

There is always a digital conversion, i use the my graphic card to convert the gamma to 1,2 (fit's good with the gamma of my PJ). So i'll loss the resolution of the output signal. Aren't there no more than 255 greyscale tones (is it only 8bit?). But when i divide 0,7V through 255 i got theoreticaly 2,7mV for 1 tone. I think it is a hard job to amplify those little voltages at high frequencies, so maybe the amplification of this signal is more important than the conversion of tones.
When the video processor of my graphic card upsample the video signal to 32bit before it converts anything (i think this might be standard because the output is even in 32bit ) the digital conversion should not be visible.
Now think what distributed light does to the tones.
Mabe it's the same in audio, i cannot hear a difference betwen a signal which is upsampled from 44 to 48 well. Even with my Stax headphone.

Soon ill try a Geforce 8600GTS flying around in my room, when the picture on my CRT screen will be better i take this card.

[perisoft]

Mark's right - there's no reason for the analog output to have any problems - it's been commodity for ages now. I can't imagine their being a difference between cards.

I'm not quite sure about the black levels thing. I use HDMI/DVI to digital panels in my work, and it certainly isn't raising the black floor for desktop work and games. With software rendering, there shouldn't be any difference - the display and card don't know the difference between movie pixels and game pixels, right?

[David_Web]

" i use the my graphic card to convert the gamma to 1,2"
A good reason to use analogue output as it is processed in 10bit (accepts 10bit LUT) on most modern graphicscards.

HDMI has no problem transmitting 0-255 RGBs.
The bad thing is that you can't seem to choose the format you want to use over it. I guess the EDID chip says what it wants and gets it.

"I compared it to a HD-Fury on a 24" CRT"
IIRC The old HD-Fury does not work well with 0-255 and crushes black and white. Someone tested it ages ago on this forum.