More Radeon oscope measurements (pics) - AVS Forum
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post #1 of 14 Old 05-15-2001, 03:29 PM - Thread Starter
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I finally borrowed the Avia DVD, and did some measurements yesterday. My main motivation for doing this was to compare the readings at the Radeon 32 DDR VGA connector to readings at the projector end of the cable. I also have an Extron RGB-118 PC interface between the PC and the projector. As the pictures show, the readings at the projector end of the cable is clearly different from the readings at the Radeon VGA connector. I did not try to isolate which of the cable and the Extron interface that had the most impact on the readings.

The oscope has a built in printer, and I scanned some of the measurements and posted them here . There are a few comments as well. Later today or tomorrow I will try some of the promising (on paper..)settings, and calibrate the black and white level of the projector with Avia.

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post #2 of 14 Old 05-15-2001, 07:09 PM
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Quote:
Originally posted by Gunnar:
I finally borrowed the Avia DVD, and did some measurements yesterday. My main motivation for doing this was to compare the readings at the Radeon 32 DDR VGA connector to readings at the projector end of the cable. I also have an Extron RGB-118 PC interface between the PC and the projector. As the pictures show, the readings at the projector end of the cable is clearly different from the readings at the Radeon VGA connector. I did not try to isolate which of the cable and the Extron interface that had the most impact on the readings.

The oscope has a built in printer, and I scanned some of the measurements and posted them here . There are a few comments as well. Later today or tomorrow I will try some of the promising (on paper..)settings, and calibrate the black and white level of the projector with Avia.

Gunnar
Gunnar: I'm having a hard time deciphering which settings you think are best according to your scoped readings.


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post #3 of 14 Old 05-15-2001, 07:32 PM
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Gunnar,

I think your measurements confirm a few of the findings that I had.

1) The most we get out of this card is about 650-660 mV without clipping.

2) Typically with brightness at +N clicks the contrast needs to be at least -(N-1) clicks to eliminate clipping. It looks like that one of the pictures you have with B=+4, C=-2 looks a little clipped.

Do you agree with these results?

One important question is when you say G=+1 is that the default position or +1 click up. I think that they may be the same anyway.

Another question is when you measure at the projector end how do you terminate the line? Are you using the exact same 75 Ohm resistor that you used at the PC end?


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[This message has been edited by John Moschella (edited 05-15-2001).]

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post #4 of 14 Old 05-16-2001, 02:12 AM - Thread Starter
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Mike,
The first group of 4 pictures shows the measurements at the projector. I think the upper left picture seems to be the best. As you can see from my handwriting the settings are: Brightness +7, Contrast -6, Gamma default, Hue default and Saturation +1. In the lower group of 4 pictures I think that the upper left seems to be the best. These lower 4 pictures shows the measurements at the Radeon card. Since the settings are very different this shows that I have to take the cables and interface into consideration when I set the overlay controls. I should have made some measurements without the interface as well. Maybe of interest for people running about the same cable lengths as me, without the interface.

John,
I made a few measurements with the resistor directly between pin 1 and 6 in the Radeon HD-15 connector, but for convenience (my HTPC is built into the rest of my "rack") I used a 3 feet cut VGA cable with the resistor connected at the end. I verified that the cable didn`t affect the readings noticeably.

I didn`t use the same resistor when I measured at the projector end of the cable, but both were 75 ohms, 1% metal film. At the projector end I used a bulkhead female BNC connector with the resistor soldered at the back. The bulkhead connector may not have been 50 ohms, but I don`t think this is significant.

1) I agree that the maximum voltage without clipping seem to be about 660mV. I was not able to get any sharper transition (the top is a bit rounded) than you can see on the 4 lower pictures. Even at low contrast settings.

2) Agree.

When I say gamma +1 I mean the default setting. Hopefully Ati will do something to the creeping sliders, as this is the only real problem I currently have with the Ati player.

Hopefully I can try some of the settings later today, and recalibrate the projector.

I forgot: OS Win98SE, Ati player 4.1, Ati beta driver 7093, DVDGenie 3.68(?), Girder remote control software. Cables: 5 feet HD-15 to 5 BNC breakout cable, Extron RGB-118 interface, about 36' 4x RG-59 cables with 75 ohms BNCs at both ends. The Extron interface has a short Monitor Breakout Cable to allow connection of an extra monitor. This cable is also in the signal chain, and may have some impact.

Gunnar

[This message has been edited by Gunnar (edited 05-16-2001).]

[This message has been edited by Gunnar (edited 05-16-2001).]
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post #5 of 14 Old 05-22-2001, 05:45 AM
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Tim Aye,

If I not mistaken, your projector is a Sony G-70. What are the settings for Brightness and Constract from the G-70 with ATI settings at B=+1, C=-2, G=+4 and S=+1? Your comments are most appreciates.

Many thanks,
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post #6 of 14 Old 05-24-2001, 08:54 AM - Thread Starter
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I tried some of my suggested settings yesterday. I noticed that when using Avia to set white and black level, I had to modify the scoped settings a bit. I`m not sure if I`m supposed to see the moving white bars in the Avia white level test pattern? According to the Avia directions the moving white bars is intended for non CRT projectors? I tried my "best" scoped setting: b+7, c-6 and g default, but with this setting I could just hardly see the darkest white bar. I had to reduce the contrast another step to see both white bars. Then my black level is probably a bit low, but the oscope is currently not available, so I don`t know how much.

With this setting I had to reduce the black level on the projector a few % to get a correct black level setting with the Avia black level test pattern (moving black bars).

Using the Avia flashing color patch test pattern (and blue filter), I had to reduce saturation 3 steps from the default. Still default value for hue.

So currently my settings are: b+7, c-7, g default, s-3, h default.

If I look at the Avia grey step pattern I can`t resolve the two darkest bars with these settings. This bothers me a bit, anyone see all bars without having to crank the gamma way up?

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post #7 of 14 Old 05-24-2001, 01:04 PM - Thread Starter
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John,
I have adjusted the brightness on my display to fit the Avia black level test. With the current setting I can see the above black bar. I`ll try different settings to see if I can resolve the two darkest bars (10 and 20 IRE?) on the grey step pattern.

I can try the +4 -3 0 setting, but I think that the Extron interface introduce some buffering of the signal that have influence on the settings, so it will probably not be comparable to yours. Unfortunately my BG-1200 won`t sync without the Extron interface.

A problem here in Oslo at this time of the year is that it doesn`t get very dark, and I can`t block the ambient light completely.

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post #8 of 14 Old 05-24-2001, 10:03 PM
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Gunnar,
I see the same effect with the moving bars on the white background in AVIA. If I use the B=+4, C=-3, G=0 setting I can see only one of the bars, however if I move C to -4 I can see both. I haven't tried calibrating my display for the C=-4 setting (this actually lower the peak white level and my picture looks kind of dark) because the directions say that at least one of the bars should be visible, which is it on my display. I think that the clicks are big steps and the correct setting for me is something between -3 and -4.

With the above settings, (+4,-3,0) and after adjusting my display using AVIA for brightness and contrast, I can see all the 10 IRE gray steps on the test patterns. If you can barly see the above black bar in the brightness test on AVIA, then you should be able to see the 10 IRE bar. I would re-check everything because the moving black bar that you should be able to see is very close to 10 IRE. You should also be careful how you calibrate the brightness with the moving black bar. It should be done with the half gray pattern on the right. If you did it with the full black screen then your brightness setting on your display may be too low. You may find that to see the moving bar with the half gray pattern the brightness may need to be turned up on your display. This cound explain the problem with the 10 IRE step.


Just for kicks I would also try the +4,-3,0 setting. Post results.

John Moschella

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post #9 of 14 Old 05-25-2001, 12:43 AM - Thread Starter
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I used the pattern with the moving bars and the half grey pattern to the right when setting the black level.

There is no difficulty in separating a 10 IRE window from the black bacground. This make me think that maybe the grey step pattern is supposed to look the way it currently does? I can see 10 bars, but the darkest bar is twice as wide as the other bars, and if I turn the gamma or brightness way up I can see that there in fact are two bars. Probably a 10 IRE bar, and the darkest bar is probably the black background. But if this is the case, why can I separate a 10 IRE window from the background without turning up the brightness/gamma?

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post #10 of 14 Old 05-25-2001, 07:49 AM
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Gunnar,
I played around with the gray scale bars last night. The last bar on the right is 7.5 IRE which you should NOT be able to see if you set the brightness correctly. The next to last bar is 10 IRE which should barely be visible above the background. I mean barely. If you can't see it at all then you probably just have to boost the brightness on your display a few percent. The third from last bar is 20 IRE which better be clearly visible.

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post #11 of 14 Old 05-25-2001, 07:58 AM
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Gunnar:
Just some suggestions and info, might be useful, and a hypothesis for your dilemma.
The AVIA black moving bars, AFAIK, uses 3 different IRE pattern, the first moving black bar is 7.5 IRE, the second moving black bar being 10 IRE and the background of those two black bars being 8.5 IRE.

This trick was used so that DVD players that cannot pass black below black level can still use AVIA to calibrate their displays - however the calibration is a bit 'off' by making a 7.5 IRE indistinguishable to an 8.5 IRE (instead of making 7.5 IRE indistinguishable to 0 IRE).

Now, I don't know what IRE AVIA is using for their gray bar ramps for blacks, is it 0 or 7.5 IRE? If it's 7.5, then the second bar would be a 10 IRE pattern - distinguishing between the two on a relatively high APL screen can be difficult (due to the closeness of 7.5 and 10). If it's 0 - and the set is well calibrated, then the 0 IRE pattern is no different than a 7.5 IRE pattern, as such it's like comparing a 7.5 IRE pattern to a 10 IRE pattern, right?

In any case, even if it's 7.5 vs. 10, you can try to see the difference by zooming onto that particular 2 pattern so you have a low APL picture. You can do this in both WinDVD and ATI DVD player, so give it a try. I used this on WinDVD and I can definitely see the difference, and I only have a 1272.

Best of luck - I'm happy someone is moving to improve on the quality of DVD playback and sharing it with us. Unfortunately, the ATI DVD player is too much a pain for me (and wife) to use.



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post #12 of 14 Old 05-25-2001, 04:05 PM - Thread Starter
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John, Muljadi
As you both say, this is probably caused by the small IRE separation between the darkest and next to darkest grey steps. I could try to zoom at the two darkest bars to see if I can resolve the two bars, but I think the result should be the same as when I show a 10 IRE window on a black background? As I said earlier, I already tried this, and the 10 IRE window was easily distinguishable from the background.

The next step in the quest for a better picture will be to add color filtering to my BG-1200. I have ordered colored c-elements that hopefully can replace the original non colored ones.

Rob,
I`ve tried negative and composite sync, and a lot of different resolutions without being able to sync. With the Extron interface, or my homemade simple interface the BG-1200 syncs without problems. I`m not sure what the problem is, but I run about 36' of cable, which introduce some attenuation of the sync signal. I have not done any measurements yet, but I prefer to keep the Extron interface, as this give me the opportunity to use an extra monitor for watching the news etc.

Gunnar

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post #13 of 14 Old 05-25-2001, 10:01 PM
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Quote:
Originally posted by budiman:



Now, I don't know what IRE AVIA is using for their gray bar ramps for blacks, is it 0 or 7.5 IRE? If it's 7.5, then the second bar would be a 10 IRE pattern - distinguishing between the two on a relatively high APL screen can be difficult (due to the closeness of 7.5 and 10). If it's 0 - and the set is well calibrated, then the 0 IRE pattern is no different than a 7.5 IRE pattern, as such it's like comparing a 7.5 IRE pattern to a 10 IRE pattern, right?

As I mentioned in my last post the last bar on the AVIA gray bars is 7.5 IRE and the next is 10 IRE. You're right seeing the 10 IRE bar with a high APL screen is going to be difficult. On my display if I calibrate the brighness using the moving black bar and the half gray screen then I can't see the moving bar with the half 100 IRE screen.

John


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post #14 of 14 Old 05-25-2001, 10:20 PM
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Hello Gunnar

Your projector can sink without the extron set the ati card to negative sink.

Rob

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