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Darin, but do you still believe that ANSI contrast matters?
I think it still matters, along with high resolution MTF and on/off CR. Off the screen is what ultimately matters, but projector values can help us determine those things. I also think ANSI CR being limited due to a reflection that shows up on some scenes with a small amount of white on black is worse that an overall washout effect, even at the same value.
Here's a challenge to you. Two projectors are given, X and Y.

From Projector X's specifications:
Native contrast: 30000:1
ANSI contrast: 300:1

From Projector Y's specifications:
Native contrast: 15000:1
ANSI contrast: 600:1

Projector X's native contrast is 2 times higher than Y's but its ANSI contrast is 2 times lower. Guess what static contrast would be in scenes at 5%, 10% and 20% ADL? At which point the X projector will begin to lose and the Y will begin to win?
This depends on multiple things (like the geometry of content in the images), but I'll answer by providing an Excel spreadsheet (attached in a zip file) to do some back-of-the-napkin kinds of measurements. If somebody grabs that they can plug in their own numbers for ADL, gamma, brightest pixel in the image, etc. I started to work on making this spreadsheet more accurate since it breaks down at extremes at least, but for a general ballpark idea I think it can work.

Assuming each has some white pixels this estimates the following for X and Y:

5%: X=2500:1, Y=5000:1
10%: X=1429:1, Y=2500:1
20%: X=714:1, Y=1429:1

They crossover with 1% at 10k:1 each by those calculations.

--Darin
 

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I guess the final projector values was for my G90 and me.;) I think you deliberately skewed the results to try to purchase my CRT off of me for cheap.:eek:


Seriously, I would like to brightness match the JVC and Marantz and see which one I prefer. I think your first pj is close to my RS25, but the second is to high in regards to on/off for the Marantz.
 

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Thank you for your work, Darin!

I extended your excel sheet. Now it doesn't have a problem with the extremes.

I added nice looking graphs :) for some projector examples and the whole ADL range.

But most of all, I added the effect of the room pollution in the contrast calculation!

You just need to give 1 value of on screen measured contrast and the "perfect" ANSI contrast possible with your projector. Please note that the "room pollution correction" made with this pair of measurement characterizes your room FULLY and is still valid for ALL projectors, so no need to change it.

Also all you need is to change the green colored cells (On-OFF and ANSI).

Have FUN! ;)

ps: somehow I got carried away (with my girlfriend...) and just wanted to share our work/results! :D
 

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I extended your excel sheet. Now it doesn't have a problem with the extremes.
Thanks Soulnight. I appreciate it.

I have a question.

My original intent with the spreadsheet was to enter system (off the screen) values. So, these took into effect whether contamination from the room was due to reflections or due to having light sources other than the projector. I like the ability to start with the projector values, add room values, and get results also.

I'm trying to understand whether this update takes into account light pollution from sources other than the projector vs from room reflections.

I made the original to try to get the point across to somebody that 40:1 system ANSI CR with 100:1 system on/off CR gives very different results for movies than 40:1 system ANSI CR with 1000:1 system on/off CR, or that for particular scenes from real movies 20:1 system ANSI CR and 1000:1 system on/off CR can result in more intra-image CR than say 80:1 system ANSI CR and 250:1 system on/off CR, for instance.

Thanks,
Darin
 

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Hi Darin!

In your excel sheet, if you put as ansi contrast value, the value off screen, then you already have the contrast with the pollution of your room. I agree.

What I added, is the possibility to give the ANSI contrast of the projector itself (very often measured at the lens (you can even correct it with a shadow to get the exact maximum value)).

And I also created a module where you can put, the ansi contrast off-screen AND the MAX ansi value off-lens. With these 2 values you get the characteristics of YOUR room. And then, you can leave this module in peace, and simulate others projectors with the MAX ANSI contrast that you can find in review etc... and at the same time see how it would be in your room.

It also enables you to see how much progress you can make in contrast if you improve your room.

Hope this helps! ;)

ps: if you really want to just give your ansi contrast you measured from the screen, and do not think about something else, just put in the module for pollution exactly the same value for the real and max ansi contrast.
 

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In your excel sheet, if you put as ansi contrast value, the value off screen, then you already have the contrast with the pollution of your room. I agree.
What I was trying to do is differentiate pollution of room reflections from pollution from other light sources. For instance, turning room lights on reduces on/off CR as well as ANSI CR. I don't see a way to include the pollution from other light sources differently than from reflections.

Thanks,
Darin
 

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BTW: One thing I meant by extreme cases are cases like the following:

System ANSI CR: 5:1
System on/off CR: 20,000:1
Image ADL: 0.00001%
Highest image pixel: 100%

The factor I was working on trying to add is that in this case about 10% of the light that goes out into the room comes back and contaminates the image. If on/off CR was done with full screen images then the on/off CR stays the same because 1.1x/1.1y is the same as x/y. However, for an image that is a single white pixel on black the white would be lower than white pixels on the full white image because it isn't getting raised nearly as much by reflections, all else being equal.

--Darin
 

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So how are we going to go about doing this, well, over the course of a couple different threads, we've come up with a method that seems to work pretty well, it requires only two free tools:

DGIndex
AVISynth

The first step is to open up all the movie's VOB files in DGIndex, and then save the project (no need to save the audio).

The second step is to run the following AVISynth Script on the movie:
Code:
mpeg2source("dgindexprojectfile.d2v")filename = "output filename"ConvertToRGB()Levels(16,0.4545,235,0,255,coring=false)ConvertToYV12()Crop(0,54,720,360)Selectevery(24,0)AssumeFps(240)colon = " : "WriteFile(filename, "current_frame", "colon", "YPlaneMin", "colon", "YPlaneMax", "colon", "AverageLuma" )WriteFileStart(filename, """ "AverageLuma for Raiders8" """)WriteFileStart(filename, """ "Frame : MinLuma : MaxLuma : AverageLuma" """ )WriteFileEnd(filename, """ "End" """)ConvertToYUY2()
A couple comments, mpeg2source should point the the project file you saved from DGIndex.
filename should point to the filename/path of the output file you want.
Crop should be adjusted to remove any black bars so they don't "contaminate" the results (could probably use autocrop).
SelectEvery is used to sample only once per second.
AssumeFPS is there to simply speed processing.

As posted, it's preferable to normalize the results into % by the following forumula:

normvalue = ( actualvalue - 16 ) / 219

I posited in the DI thread that the Levels command could be used to apply display gamma to the above script to convert from %stim to APL.

Hi,

I downloaded both DGIndex and AVISynth.

But the tutorial above is not enough for me. :( Could someone detail the steps for someone who has never used any of this software?

Do you need .mt2s files. Or do mkv files work as well?

Thank you. I am willing to participate to thios thread with a bit of help! ;)
 

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Discussion Starter · #90 ·
Probably the easiest way is to get Staxrip/Staxmedia, with that you can just drag and drop about any file type into it and it will create the .avs files for you. Then you can just edit them per above and run them. You should be able to just open them in Windows Media Player, or maybe use Virtualdub to "render" them.
 

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But the tutorial above is not enough for me. :( Could someone detail the steps for someone who has never used any of this software?
Great to see that you want to do this too. I just got this setup last weekend, but sorry that I didn't keep track of the steps I had to take. You may have figured it out by now, but one important step I recall finding in a thread here about this (probably the original CR thread stanger89 was referring to) was that I had to put DGDecode.dll from DGIndex in \Program Files (x86)\AviSynth 2.5\plugins.
Does it only work with vob files? (dvd?)
How do you proceed with blu-ray/m2ts/mkv files?
The above does only work with DVD level. My goal today was to get this working for HD. I found DGAVCIndexNV, but not sure if that version will work on my PC. When I went to try it a few days ago I got an error that I needed to download some more stuff from a DG toolkit, which I plan to look into today.


Since the first tools were limited to DVD I got "Any Video Converter" to convert HD files to mpeg2. I remember that my virus scanner caught something trying to download an ad program and I think it might have been this one, but I'm not sure. In any case, I would prefer to analyze the original instead of converting first, so hopefully can get this process working for HD files.


--Darin
 

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Discussion Starter · #92 ·
For HD, there are a few options. For AVC there's:
http://www.digital-digest.com/software/DGAVCDec.html

ffmpeg source can load just about anything:
http://avisynth.nl/index.php/FFmpegSource

The easiest way may be StaxRip:
http://staxmedia.sourceforge.net/

It includes all the source plugins you're likely to need, and the simple step of opening a video in it will perform whatever steps are necessary to create an avs file. Though one thing to watch out for, it seems to like to default to expanding video to PC levels, so be aware of that.
 

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I downloaded Staxrip.

Seems like a magic tool...but I'm not a magician! :rolleyes:

I would need your help.

What do I need for an .avs file? How do I use it?
How do I run a script? With which software? Is it with the avsfile?

Do I need to te reencode (lossy) the mkv I made from the m2ts blu-ray file?

Thank you! :)
 

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OK guys, I got it to run. Still runs... but I could already look at the first results Blu-ray Django unchained!). But... I'll tell you only when it's finished! :rolleyes:

I do have question:

Is the average luma given in the text file already gamma corrected (with a gamma or 2.2)?
It seems so because the value are so small (range about 9% Avg luminance).

But I do not see where in the script is it written! :p
 

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Do I need to te reencode (lossy) the mkv I made from the m2ts blu-ray file?
I don't believe so.


I'll have to get back to this, but from an mkv I've gotten a .raw file that I ran through DGAVCIndex by following these instructions for avidemux:


RAW: specialist needs, not handled by avidemux afterwards in this format.
extracting the video only to raw:
leave both video and audio output set to [Copy]
set Output Format to [Video Only]
now use save and give it a name, don't add an extension.
The video should be saved with extention .raw

Now I need to get this to run through avisynth. I don't recall whether I need a special version of that for HD.


--Darin
 

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So here is what worked for me in the end:

I used StaxRip, opened the mkv in it and got from that this avs script in the temp files folder:

Code:
LoadPlugin("D:\Video\Software\StaxRip\Tools\Plugins\ffms2\ffms2.dll")
FFVideoSource("D:\Video\Django_Unchained\Django_Unchained_t00.mkv", cachefile = "D:\Video\Django_Unchained\Django_Unchained_t00 temp files\Django_Unchained_t00.ffindex", fpsnum = 24000, fpsden = 1001)
Crop(0, 140, -0, -140)
Unfortunately it didn't work like that. So I downloaded the ffms2 plugin separately and changed the path in LoadPlugin to the new ffms2.dll.

The complete avs script (that I opened with media player classic) is:

Code:
LoadPlugin("D:\Video\Software\ffms2-2.20-icl\x86\ffms2.dll")
FFVideoSource("D:\Video\Django_Unchained\Django_Unchained_t00.mkv", cachefile = "D:\Video\Django_Unchained\Django_Unchained_t00 temp files\Django_Unchained_t00.ffindex", fpsnum = 24000, fpsden = 1001)
Crop(0, 140, -0, -140)

filename = "Django"
ConvertToRGB()
Levels(16,0.4545,235,0,255,coring=false)
ConvertToYV12()
Selectevery(24,0)
AssumeFps(240)
colon = " : "
WriteFile(filename, "current_frame", "colon", "YPlaneMin", "colon", "YPlaneMax", "colon", "AverageLuma" )
WriteFileStart(filename, """ "AverageLuma for Django" """)
WriteFileStart(filename, """ "Frame : MinLuma : MaxLuma : AverageLuma" """ )
WriteFileEnd(filename, """ "End" """)
ConvertToYUY2()
One thing I'm wondering about is the line AssumeFps(240). Why are we doing this?

Thanks again for your help!
 

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And here the results for Django unchained if you DO take into account the black bars into the ADL analysis (so uncropped).



Average movie ADL: 6.00%


;)
 

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OK guys, I got it to run. Still runs... but I could already look at the first results Blu-ray Django unchained!). But... I'll tell you only when it's finished! :rolleyes:

I do have question:

Is the average luma given in the text file already gamma corrected (with a gamma or 2.2)?
It seems so because the value are so small (range about 9% Avg luminance).

But I do not see where in the script is it written! :p

I Do know now! ;) I found it. :D

Code:
Levels(16,0.4545,235,0,255,coring=false)
This line converts the APL of each pixel into ADL with a approximation of the gamma 2.2 (which is 1/0.4545).

:cool:
 
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