DLP, Checkerboard, and 3D - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 21 Old 06-25-2011, 11:14 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
I have not been able to find an adequate layman's explanation for how DLP uses the checkerboard format to display images in both 2D and 3D, so I decided to try and explain it myself.

Please feel free to read and comment.

Attachment 228720

EDIT: Further discussion here http://www.avsforum.com/avs-vb/showt...9#post20625259

 

DLP, checkerboard, and 3D.pdf 165.0263671875k . file

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
Sponsored Links
Advertisement
 
post #2 of 21 Old 06-26-2011, 12:20 AM
Senior Member
 
Bruce M.'s Avatar
 
Join Date: Jan 2002
Location: Seattle, Washington
Posts: 374
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Dig it. Best introductory-level treatment I've seen to date. Charts, and their explanations, are what make it work.
Bruce M. is offline  
post #3 of 21 Old 06-26-2011, 08:58 AM
AVS Special Member
 
taz291819's Avatar
 
Join Date: Jan 2003
Location: Huntsville, Al
Posts: 5,983
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Nice job on the write up!

Currently testing 3D with Sammy DLP, shutter glasses, and HTPC
taz291819 is offline  
post #4 of 21 Old 06-26-2011, 09:34 AM
AVS Special Member
 
PaulGo's Avatar
 
Join Date: Apr 2003
Location: North Potomac, MD
Posts: 3,626
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 19
PaulGo is online now  
post #5 of 21 Old 06-26-2011, 03:15 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Quote:
Originally Posted by Bruce M. View Post

Dig it. Best introductory-level treatment I've seen to date. Charts, and their explanations, are what make it work.

Quote:
Originally Posted by taz291819 View Post

Nice job on the write up!



Thanks for the comments.

Yes. I drew from all of those sources. I've found that some people read those and still do not understand how it works. These are the people who swear checkerboard is 960 x 1080 or 1920 x 540 per eye. They still think in square pixels, and not diamonds.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #6 of 21 Old 06-26-2011, 05:34 PM
AVS Addicted Member
 
walford's Avatar
 
Join Date: May 2003
Location: Orange County, CA
Posts: 16,789
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
I disagree with the following staatement.

HP’s “Wobulation” or TI’s “SmoothPicture” is the process of shifting the light from the DLP mirrors from the locations shown as purple squares
(L), to the locations shown as orange squares (R) in figure a. This happens very fast, and the combined sub-frames form one complete video
frame.


A 3D video frame can not contain both the left eye and right eye images simultanously on a DLP screen.

Each time a "wobble" occurs(every 120th of a second) the video frame changes from left to right or right to left and the white DLP Linik white flash is displayed on the screen to control the active shutter glasses lenses.
walford is offline  
post #7 of 21 Old 06-26-2011, 05:44 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Quote:
Originally Posted by walford View Post

I disagree with the following staatement.

HP’s “Wobulation” or TI’s “SmoothPicture” is the process of shifting the light from the DLP mirrors from the locations shown as purple squares
(L), to the locations shown as orange squares (R) in figure a. This happens very fast, and the combined sub-frames form one complete video
frame.

A 3D video frame can not contain both the left eye and right eye images simultanously.

Each time a "wobble" occurs(every 120th of a second) the video frame changes from left to right or right to left and the white DLP Linik white flash is displayed on the screen to control the active shutter glasses lenses.

The quoted passage was describing how a DMD chip paints a 2D frame of video. DLPs use the checkerboard format to use half the number of mirrors in order to render all of the number of pixels. And 120th of a second is very fast to me.

From the preceding paragraph
Quote:
Figure a. is a representation of the left and right sub-frame pixels in a DLP (checkerboard) 2D input.


"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #8 of 21 Old 06-26-2011, 07:00 PM
AVS Addicted Member
 
walford's Avatar
 
Join Date: May 2003
Location: Orange County, CA
Posts: 16,789
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
I agree 120th of a second is fast and it is the minimum refresh rate used by all 3D flat panel TVs in order to display 1080p per eye 3D content Many LCD/LED 3D TVs use as 240 fps refresh rate and some others even have 480 fps refresh rate.
walford is offline  
post #9 of 21 Old 06-26-2011, 08:01 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Quote:
Originally Posted by walford View Post

I agree 120th of a second is fast and it is the minimum refresh rate used by all 3D flat panel TVs in order to display 1080p per eye 3D content Many LCD/LED 3D TVs use as 240 fps refresh rate and some others even have 480 fps refresh rate.


I don't see the point of your post. This thread is not about flat panel displays nor their refresh rates.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #10 of 21 Old 06-26-2011, 08:34 PM
AVS Special Member
 
PaulGo's Avatar
 
Join Date: Apr 2003
Location: North Potomac, MD
Posts: 3,626
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 19
DLP refresh rates cannot be compared to LCD or Plasma since by using mirrors their is no decay time so ghosting does not become a problem. The quality of a DLP display is actually quite amazing. I believe for digital projection DLP is the preferred method.
PaulGo is online now  
post #11 of 21 Old 06-27-2011, 07:58 AM
AVS Addicted Member
 
walford's Avatar
 
Join Date: May 2003
Location: Orange County, CA
Posts: 16,789
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
I agree that no ghosting or video crosstalk can occur on the DLP screen due to the speed of the DMD chip. However ghosting or crosstalk can occure if the active shutter glasses used do not respond fast enough.
walford is offline  
post #12 of 21 Old 06-27-2011, 01:46 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Can we get back on topic, please?

Increasing refresh rate to compensate for flat panel display flaws and cheaply made 3D glasses have little if anything to do with DLP technology.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #13 of 21 Old 06-29-2011, 10:32 PM
Member
 
DanielJoy's Avatar
 
Join Date: Apr 2010
Posts: 115
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
its amazing that 07 3d tv tech smokes 2011 3d tv tech

Intel I7 920 overclocked 4ghz
Asus Rampage Extreme II
2 Ge-force 480 in SLI
295 PhysX Card
12gb 2000mhz ram
Intel SSD RAID
BR RW
1000w Sony
Mitsubishi 65" 3d HDTV
NVIDIA 3D Vision
DanielJoy is offline  
post #14 of 21 Old 06-29-2011, 11:58 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
+1

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #15 of 21 Old 06-30-2011, 07:30 AM
Member
 
Waltm's Avatar
 
Join Date: Nov 2004
Posts: 51
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by walford View Post

I agree that no ghosting or video crosstalk can occur on the DLP screen due to the speed of the DMD chip. However ghosting or crosstalk can occure if the active shutter glasses used do not respond fast enough.

If using DLP-Link active shutter glasses that blank out the sync flash at the beginning of each frame (left and right eye) then it seems to me there shouldn't be any ghosting or crosstalk due to the shutters not being fast enough. If that were the case you would still see the lighter image due to the sync flash, like you do when using IR sync glasses with DLP-link active.
Waltm is online now  
post #16 of 21 Old 06-30-2011, 01:43 PM
AVS Addicted Member
 
walford's Avatar
 
Join Date: May 2003
Location: Orange County, CA
Posts: 16,789
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
DLP link glasses do not blank out the white flash they receive and process the white flash and if they do not respond and change shutters fast enough they can cause video cross talk.
walford is offline  
post #17 of 21 Old 06-30-2011, 05:06 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
We know that the DLP-Link glasses receive the DLP-Link flash.

The flash creates a "wash-out" or "tinted black" effect in the picture seen by the naked eye and the effect is still visible with IR glasses.

That effect is not seen through the DLP-Link glasses (lens timing?), so they effectively block it from view.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #18 of 21 Old 07-01-2011, 01:29 PM
Senior Member
 
hceuterpe's Avatar
 
Join Date: Aug 2007
Posts: 491
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I'm curious as to what the "tinted blacK' is supposed to look like.
Do you have an example?
I've heard of the "red tint", and seen it, but I do not know what tinted black is supposed to look like.
hceuterpe is offline  
post #19 of 21 Old 07-01-2011, 01:46 PM
Senior Member
 
hceuterpe's Avatar
 
Join Date: Aug 2007
Posts: 491
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
It sounds like to me that they are implementing 3D much like doing an IVTC on interlaced HD material to get a progressive scanned picture.

It's definitely not quarter, or even half resolution. In fact, unless LCD magically has more pixels than, 1080p it seems it should be on par, assuming your glasses are good. If anything, it sounds like LCD was unable to do checkerboard because it doesn't refresh fash enough, so they had to do a dual view approach (not to mention forcing everyone to buy new AV receivers),
hceuterpe is offline  
post #20 of 21 Old 07-01-2011, 03:33 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Quote:
Originally Posted by hceuterpe View Post

I'm curious as to what the "tinted blacK' is supposed to look like.
Do you have an example?
I've heard of the "red tint", and seen it, but I do not know what tinted black is supposed to look like.

Same thing. I think Samsung DLPs have the red tint, my mits has a blu-green tint.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
post #21 of 21 Old 07-01-2011, 03:38 PM - Thread Starter
AVS Special Member
 
Augerhandle's Avatar
 
Join Date: Jan 2009
Posts: 2,586
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Liked: 47
Quote:
Originally Posted by hceuterpe View Post

It sounds like to me that they are implementing 3D much like doing an IVTC on interlaced HD material to get a progressive scanned picture. ...[snip]

It's interleaved, not interlaced. Interleaving combines information from the same frame, so theres no "jaggies" or other motion artifacts.

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
 
Augerhandle is offline  
Reply 3D Tech Talk

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off