Flickering screen (no user interaction)

[wmattias]

Hi!

I'm wondering if it's normal behavior for the screen to "flicker".

The flicker is not related to moving the screen around or re-drawing. I'm just looking at the screen and not interacting at all.

The flicker is visible on all screens/programs. It is also visible when the screen dims down.

The flicker varies in intensity (from no flicker to very prominent flicker) depending on the shape of the graphics and its color. It is most prominent if you have a horizontal line (or bar) in a color that is not extreme (full black, full red, full white, etc). For example, the grey lines that you see on the screen after you've typed a few entries/calculations in the Home screen flicker very prominently. Also if you have a colored area that spans the screen horizontally in a color that is not extreme.

If the horizontal line is pure black or white (or for example pure red), there is no visible flicker. If the line is vertical, there is also no visible flicker.

It's HP Prime G2, brand new. I really like it overall, but the flicker is really fatiguing so I'm thinking about returning it. But I wanted to check here first if it's possibly just a defective unit, or if it's just part of the design of the HP Prime.

[mfleming]

There was a discussion of screen flicker some months back, involving refresh rates, personal perception, etc. I seem to remember a consensus that most peopld didn't notice it (me included). You may be one of the lucky few who can Maybe someone can post a link to the thread...

[pinkman]

I found this interesting thread here.
And this other one.

[wmattias]

Hi!

Thanks for the articles and tips!

I looked at those posts in detail, but the issues appear to be different:

1. issues with flicker when interacting with the screen (scrolling, etc). As someone pointed out, that’s probably related to the software not using double buffering for the graphics.

2. Issues with random flicker - lines appearing here and there over the screen. This is also different from the issue I’m facing. I have no issues here.

3. The problem I’m facing is with a static screen (no interaction or animation). The flickering is dependent on the color of the line, and mostly visible when it’s a long horizontal line. I ran the self test, but since the test patterns have fully saturated colors the phenomenon doesn’t occur. It’s almost like the calculator is using poorly implemented PWM to reduce the color saturation - but that doesn’t make sense from what I know about TFT screens.

[cyrille de brébisson]

Hello,

What type of lighting are you using around you?
Do you still see the effect when going outside in sunlight?
Do you have a G1 or G2 calc? I do not know for G1, but G2 is supposed to have a refresh rate of 55Hz, 1/2 way between the US 60Hz and the rest of the world 50Hz frequencies used in electricity (and therefore any frequency dependent lighting). This is supposed to avoid "standing wave" of synchronized LCD with light and make the phenomenon less visible...
Some people are also naturally more sensible to this effect...

Cyrille

[wmattias]

Hi Cyrille!

Thanks for trying to help!

Yeah, I've tried out in sunlight (and in a dark room), but the flickering remains there.
So it doesn't seem to be related to stroboscope effect of artificial lightning.

It's a G2 calc, with the latest revision:
Application: 20181016 v14181
Operating System: V2.060.650

I noticed that the flickering also depends on the viewing angle (the viewing angle will change the perceived color saturation of the lines). If I tilt the calculator forward, then the horizontal lines in "Home" appear black and the flickering is not visible.

I realized it's actually possible to record the flickering using my iPhone X, you can actually clearly see the phenomenon in the video. The bottom horizontal line (which is black) is not flickering, but you can clearly see how the other horizontal lines are flickering. Or is it just me who can see it? Maybe I'm going crazy!

(I tried to attach the Video to this message but the hpmuseum.org site says that this type of attachment is not allowed (.MOV). I've put it on Google Drive instead: https://drive.google.com/open?id=17_hToc...uPDaN63P6d)

[Jacob Wall]

(12-18-2019 12:15 AM)wmattias Wrote:  Or is it just me who can see it? Maybe I'm going crazy!

I have the same experience and it's certainly obvious to me from your video that it's the same thing I am seeing. I find that when looking from the side, the flicker stops on G2 screens.

I see a very faint flicker on G1 screens too, but it's hard to tell under usual circumstances.

[TheLastMillennial]

I also think the flickering is very noticeable. I even mentioned it in my massive review. I thought it was of low refresh rate, but 55hz should be more than enough to not see it with the naked eye. Perhaps something else is going on? I also have a G2 on the latest beta. This has been an issue ever since I got my Prime.

[cyrille de brébisson]

Hello,

Any flickering seen on vidéos and on other screens is, unfortunately not a good indicator of reality due to the camera and viewing screens effect super-imposing on the original issue....

Anyhow, I looked again, and I can not see anything wrong on my end :-(, but my eyesight is poor, so I am not a good test subject...
Well, at least I can not see the flicker that you describe. I can definitely see some "buzzing" around the blue "top ribbon", but not on the horizontal divider lines...

I really wonder what might be wrong... Is it a systemic issue, due, for example, to the dithering algo used by the LCD chip?
or something particular to your calculators (like LCD on the tail end of specs)?

Cyrille

[Dirk.nl]

On my HP-Prime G2 I can't detect any flicker on the screen!
I can also see the screen very well at a reasonable angle.

SW: 2.1.14341 (2019 11 20 Beta)
HW: D
CAS: 1.5.0
OP: V2.060.650

[Stevetuc]

(12-18-2019 12:21 PM)Dirk.nl Wrote:  On my HP-Prime G2 I can't detect any flicker on the screen!
I can also see the screen very well at a reasonable angle.

SW: 2.1.14341 (2019 11 20 Beta)
HW: D
CAS: 1.5.0
OP: V2.060.650

G2 rev 2?

[Dirk.nl]

Oh, I didn't understand that there was already a rev 2 of the G2.
At “About HP Prime” nothing is stated about a rev 2.
Because I have owned my G2 for almost 1.5 years, I think I have rev 1.

[chromos]

(12-18-2019 12:15 AM)wmattias Wrote:  ... I've put it on Google Drive instead: https://drive.google.com/open?id=17_hToc...uPDaN63P6d

I'm not trying diminish your observation, but this video doesn't proof anything, because there is such many involved things: Prime screen with refresh rate 55 Hz captured with camera with 30 fps. And, I'm seeing it on 60 Hz monitor. Even when I observe massive flickering, what conlusion one can take from it?

[toml_12953]

(12-18-2019 12:47 PM)Stevetuc Wrote:  

(12-18-2019 12:21 PM)Dirk.nl Wrote:  On my HP-Prime G2 I can't detect any flicker on the screen!
I can also see the screen very well at a reasonable angle.

SW: 2.1.14341 (2019 11 20 Beta)
HW: D
CAS: 1.5.0
OP: V2.060.650

G2 rev 2?

What is G2 rev. 2? I've never heard of it before. How can it be distinguished from a G2 rev. 1?

[Stevetuc]

(12-18-2019 12:47 PM)Stevetuc Wrote:  

(12-18-2019 12:21 PM)Dirk.nl Wrote:  On my HP-Prime G2 I can't detect any flicker on the screen!
I can also see the screen very well at a reasonable angle.

SW: 2.1.14341 (2019 11 20 Beta)
HW: D
CAS: 1.5.0
OP: V2.060.650

G2 rev 2?

Sorry guys, my pitiful attempt at humour!

[rprosperi]

(12-18-2019 06:16 PM)Stevetuc Wrote:  Sorry guys, my pitiful attempt at humour!

It's a tough crowd when it comes to stuff like that.

If it helps, I got it. (probably doesn't)

And take satisfaction knowing that a few dozen folks have been searching the web for info on Prime G2 rev 2...

[toml_12953]

(12-18-2019 06:16 PM)Stevetuc Wrote:  Sorry guys, my pitiful attempt at humour!

Whew! I was all set to go on another international hunt for the new model! Since it was a only a joke, I can safely put my plastic back. Or use it on "The C64", a Commodore 64 clone.

[wmattias]

Hi!

Right, I understand there's sampling issues, etc, with videos of TFT/etc screens. What surprised me was that the visual effect was exactly the same when I viewed it on the video and in reality. It's not meant as a technical proof, just that I perceive the flickering video and the calculator screen in the same way. If you step the video frame by frame you can see how the grey horizontal lines shift in color, while the solid black does not. Again, I don't know if that is a property of the video recording or that is actually how my HP Prime screen is behaving.

Anyway, I tested to write a test program to try to understand in what scenarios I perceive the flickering. From that, it is clear that fully saturated single lines don't flicker - while non-fully saturated lines do. Exception is if the whole screen has the same non-fully saturated color.

I'm beginning to believe that it's this particular calculator that is "broken". I showed the test patterns to my girlfriend, and her reaction was: "Wow, what's wrong with your calculator? Why is it blinking like that?"

Jacob/TheLastMillenial => You seem to be having the same issue as me. How does your calculators react to the program below?

Cyrille/Dirk => Any chance you can try to the program below? See any flicker?

Below is the test program I used:

Code:


EXPORT ScreenTest()
BEGIN

C:=#DDDDDDh;

RECT();
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("Flicker", 140, 110);
WAIT(-1);

RECT();
FOR X FROM 0 TO 319 STEP 2 DO
  LINE_P(X,0,X,240,C);
END;
TEXTOUT_P("No Flicker", 130, 110);
WAIT(-1);

RECT();
FOR X FROM 0 TO 319 STEP 2 DO
  LINE_P(X,0,X,240,C);
END;
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("Flicker", 140, 110);
WAIT(-1);

RECT();
FOR Y FROM 0 TO 239 STEP 1 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("No Flicker", 130, 110);
WAIT(-1);

RECT();
C:=RGB(100,100,200);
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
C:=RGB(200,200,255);
FOR Y FROM 1 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("Flicker", 130, 110);
WAIT(-1);

RECT();
C:=#DDDDDDh;
X:=20;
FOR Y FROM 0 TO 239 STEP 1 DO
  IF even(Y) THEN X0:=0; ELSE X0:=1; END;
  FOR X FROM X0 TO 319 STEP 2 DO
    PIXON_P(X,Y,C);
  END;
END;
TEXTOUT_P("No Flicker", 130, 110);
WAIT(-1);

RECT();
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,160,Y,C);
  LINE_P(161,Y,319,Y,#000000);
END;
TEXTOUT_P("Flicker", 60, 110);
TEXTOUT_P("No Flicker", 215, 110);
WAIT(-1);

RECT();
C:=RGB(0,0,255);
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("No Flicker", 130, 110);
WAIT(-1);

RECT();
C:=RGB(200,200,255);
FOR Y FROM 0 TO 239 STEP 2 DO
  LINE_P(0,Y,320,Y,C);
END;
TEXTOUT_P("Flicker", 140, 110);
WAIT(-1);

RECT();
TEXTOUT_P("Test Finished", 120, 110);
FREEZE;
END;

[toml_12953]

(12-19-2019 12:32 AM)wmattias Wrote:  I'm beginning to believe that it's this particular calculator that is "broken". I showed the test patterns to my girlfriend, and her reaction was: "Wow, what's wrong with your calculator? Why is it blinking like that?"

Nope, it's not just your calculator. I ran the program you supplied and it flickers on the same screens yours does. I'm running 2.1.14341 (2019 11 20 BETA) on a HW D G2.

[Stevetuc]

(12-18-2019 11:35 PM)toml_12953 Wrote:  

(12-18-2019 06:16 PM)Stevetuc Wrote:  Sorry guys, my pitiful attempt at humour!

Whew! I was all set to go on another international hunt for the new model! Since it was a only a joke, I can safely put my plastic back. Or use it on "The C64", a Commodore 64 clone.

I'd be very careful if I were you, apparently there is a rev 2 C64 ..https://youtu.be/p3bwYDRk42w