Discussion about Display Motion Physics (BFI, Color Mixing, Video Issues, Etc)

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 08 Nov 2021, 16:49

mynm wrote:
08 Nov 2021, 11:15
...
Update: Your screen recorder is EVEN worse than I thought...

Your screen recorder is doing some vertical tearing artifacts, by capturing part of one frame and part of the next frame. It's not even just stuttering (missed frames) -- it's mixing multiple frames into the same frame. So all prior video evidence is 100% wild good chase to red herrings, and must be completely considered invalidated.

Here's some example freezeframe grabs that shows some momentary color distortions (not sure of video file fault or website fault)

Color disortion artifact in one of your videos:
screen-record-1.png
screen-record-1.png (220.02 KiB) Viewed 545 times
Vertical tearing distortion artifact in another one of your videos. This is ironclad proof of a VSYNC violation.
screen-record-2.png
screen-record-2.png (260.7 KiB) Viewed 545 times
There are many weak links of videos:
(A) Screen recorder framerate=Hz
(B) Screen recorder correctly capturing frames between VSYNC's rather than across VSYNC's (half of one refresh cycle
and half of a different refresh cycle)
(C) Screen recorder saving the correct frame rate;
(D) Screen recorder not injecting any pulldown effects (e.g. properly doing 1:1:1:1:1:1 rather than accidentally 1:2:0:1:2:0)
(E) Website doesn't convert frame rate (right now the website you uploaded it to, reduced the frame rate to 30fps). You can bypass this by using a GDrive or Dropbo link, but that doesn't fix the other factors...
(F) Viewer display is same refresh rate as screen recorder frame rate (viewer display Hz original display Hz)
(G) Viewer browser or video player is not frameskipping (e.g. not stuttering the video playback)
etc.

For example, when I play 60fps TestUFO videos on a 144Hz display, some effects are gone.

If one of the above variables fail, you still have an invalidated video.

Can you definitively guarantee (A) AND (B) AND (C) AND (D) AND (E) AND (F) AND (G) simultaneously, for example? No.

You're asking questions several grades ahead -- please go back to the basics first and understand the basics first.

My recommendation is
1. Ignore screen recording.
2. View TestUFO links only.
3. Share TestUFO links instead.
4. If you need videos, use pursuit camera.
5. If you are writing peer reviewed literature, write academic and scientific papers using TestUFO links or pursuit camera.

If you must screen record, test the original TestUFO and screen recorder with a high speed camera, and single frame step-by-step the footage to make sure they are identical and properly perfectly recorded. You must absolute vet every single frame, one at a time. One method is to use a high speed video camera pointed at the playback of your video recorder to compare against the high speed camera record of your TestUFO animation. Another method is to single frame step by step the video and make sure it is a known sequence that you understand. Then explain the variables required to properly play back the video (e.g. which refresh rate and which video player to play the video back in, as different players will stutter differently). However, there is too much error margin with screen recording.

Better yet, you can more easily specify fewer number of variables ("I viewed this TestUFO animation while my display was configured to 45Hz") to help the viewer configure their viewer-side variables to match your source-side variables.
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 08 Nov 2021, 17:37

Chief Blur Buster wrote:
08 Nov 2021, 16:49
mynm wrote:
08 Nov 2021, 11:15
...

Color disortion artifact in one of your videos:
screen-record-1.png

Vertical tearing distortion artifact in another one of your videos. This is ironclad proof of a VSYNC violation.
screen-record-2.png

Those artifacts are what I have edited to test if the frames were mixed. The first one is at 30 Hz but I have posted other one with 60 Hz. It's changing the color of the ufo one frame in red and the next in green. And what I see is one ufo with a mixed color.

The second video is a 60fps video and what I have edited is the first frame to see the left half part of the ufo and the next frame the right half of the ufo. And I get one ufo with the two parts together but with its color mixed with the white part.

Thank you so much again for the response and the info. I will try to properlly read it and answer you.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 09 Nov 2021, 06:40

Please don't put this on my posts:

[Editor's Note: These videos are invalid evidence as they are (A) not pursuit camera and/or (B) does not guarantee framerate=Hz at source & destination viewing public]

Those video are a screen recorded with software and are edited as I said to do the tests.

I have been respectful with you. This is the best forum I know to talk about these topics. I said I don't have readed completelly your post and that I will try to response them properlly asap. But it seems that you even have readed mines or tried to understand them. And sorry now I see some gramma mistakes that maybe can cause them to be less understables.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 10 Nov 2021, 12:34

Great, now that we've determined one of the weak links (but there are still many weak links for videos that invalidate videos -- even if these are fixed). Let's get back on topic of analysis.

For now, let's ignore video & bypass videos.

Based on direct reading of www.blurbusters.com/area51 as well as my explanations, do you understand what I am talking about in my previous posts (ignoring discussion about videos)?

I'd be happy to help and discuss effects seen in realtime TestUFO watching (not videos of TestUFO, since this specific type of test is not reliable to reproduce in video for many more reasons than the reasons explained in this thread).

Screen recorder & videos are generally never reliable for mandatory symmetry frame:refresh demos. Especially for software BFI, because even if some things are fixed, there are Laws of Physics involved because of file format limitations one way or another. This prevents certain file formats like .MP4 .MOV .MPEG from being very practical for certain types of online teachings of frame-accurate display physics. There is currently no video file format compatible with FireFox and Chrome that successfully preserves TestUFO Software BFI when played back in a computer-independent way (unknown viewer), though one can only try their best to specify the necessary variables so that users can pre-configure a computer to attempt to play video in original perfect frame:refresh symmetry.

There are currently severe limitations of many file formats (including .MPEG .MPEG2 .MP4 .AIFF .MOV .M4V etc) that doesn't work for TestUFO BFI, whether it's camera-recorded or screen-recorded.

It does not matter if it is a camera or a screen recorder. The video file formats enforce rather severe limitations that makes it hard to reliably teach/explain software BFI behaviors.

It's often too timestamp-lossy, as we need perfect lossless frame:refresh playback symmetry for proper demonstration of software BFI. Even a single dropped frame can cause massive distortions:
- Single duplicated/dropped frame caused by browser inefficiency;
- Single duplicated/dropped frame caused by a reader's computer not being fast enough;
- Single duplicated/dropped frame caused by operating system not playing video files smoothly;
- Single duplicated/dropped frame caused by differences in refresh rate between original system and Internet user system
- Single duplicated/dropped frame caused by inefficiencies in different video players;
- Single duplicated/dropped frame caused by precision limitations of a timestamp data format in the specifications of a specific video file format;
- Single duplicated/dropped frame caused by automated server re-processing by a host website (e.g. YouTube)

Due to laws of physics, and the limitations of video being unable to guarantee perfect frame:refresh symmetry on all random Internet-browser viewing systems, I can't advocate use of video files for teaching software-based black frame insertion. It may work on some systems, but will not always work on random Internet viewers.

A big reason why TestUFO became so famous/trusted and scientific is that it is one of the few tests that has a framedrop-detector when run in native Javascript: It knows whenever it's stuttering. You need a special auto-adapting video file format that automatically adapts to a viewer refresh rate, with an indicator that validates/invalidates perfect frame:refresh sync. Unfortunately, MPEG, MPEG1, MPEG2, MPEG4, Ogg-Vorbis, VP9, H.263, H.264, H.265, H.EVC, all don't have the necessary video file playback features to successfully guarantee frame:refresh sync on all viewer systems.

Certain display physics such as simulated strobing (software BFI) requires sustained perfect sync between frames and refresh cycles, as a single framedrop creates a noticeable flicker / distortion to a specific display physics. All the error margins needs to be removed.

Happy to educate & help explain things through the Right Tool for the Right Job.
For that, software BFI needs to be done through refreshrate-synchronized animations.
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 10 Nov 2021, 12:53

P.S. Any further discussion about video, or use of video, is pointless.

It's just tantamount to asking an English Teacher to teach math (in a non-English context) or asking a Calculus teacher to teach biology (in a non-Calculus context).

Software based black frame insertion needs to be microsecond-precise to avoid breaking effects (e.g. possible visible random flickers, possible loss of double images, etc).

Two years ago with a display manufacturer, we traced a display-flicker bug to a 10-microsecond error in backlight based BFI. Even a 10 microsecond error in black frame can create human-visible flicker. A display that flashes each frame for 1.000 milliseconds. But then the display sometimes flashed certain frames (refresh cycles) for 1.01 milliseconds. That's 1% more photons, 1% brighter. It's faint but noticeable. 10 microsecond difference!

Videos are not microsecond-precise sync between recording:playback when the recording system and playback system are totally different in opposite ends of the Planet Earth.

For general online education about real-time nature of microsecond-precise black frame insertion, video just isn't the Right Tool for the Right Job, full stop, no questions. Arguing the use of video to record software BFI is just arguing 2+2=5. We can't do the metaphorical equivalent of arguing a Math problem in an English class, or a biology problem in French language class, or a biology dissection problem in keyboard touchtyping class. This isn't Twitter or a Facebook comments board.

Even if colors are fixed, there are other limitations about video that prevent currently-invented video file formats from teaching real-time black frame insertion science, except in certain cases (such as slow-motion videos from a high speed camera etc -- but that's not real-time anyway).

Look, you've successfully whac-a-mole a few problems about videos and solved a few problems. Sometimes video will work, but here we're all about online education about display physics. There are over 1000 different refresh rates at 60 Hz -- one GPU is outputting at 60.001366Hz and another GPU is outputting 59.99983Hz, due to clock manufacturing differences. You can even view this problem at www.testufo.com/refreshrate#digits=8 ...

What is advertised at 60.0000000 Hz never happens, and its error margin is big enough to interfere with online cross-the-Internet education of software BFI. Read above, 10 microseconds creates human-visible BFI issues!

Video files are useful for a lot of situations. It's the correct tool for many TestUFO tests that are less temporal-sensitive. However, BFI is one of the most temporally-sensitive display physics, where temporal violations are much more hugely amplified/cascaded. Again, 10 microseconds is human visible for a hardware-based aberration, since the ratio of 1.000ms:1.010ms (in LED backlight flash per frame) is a 1% difference in the number of photons hitting the human eyeballs for that specific flashed display frame. Especially if the aberration/deviation instances per second is at a fairly low frequency (e.g. 5 timing aberrations per second) in the midst of consistency.

Video files are not microsecond accurate in these cases. Video files don't guarantee original:destination perfect sync. It requires a software program with realtime sync to speedup/slowdown BFI to the actual native final refresh rate you're running, to the perfection of a microsecond.

Let's get back on topic. Since it's not possible to guarantee video meeting the criteria of necessary online education of software BFI. Otherwise there's no point, and the thread can be closed/locked.
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 10 Nov 2021, 13:17

Also, now I must preface some limitations.

How TestUFO Achieves Microsecond Accuracy In Some Tests
(Currently-invented Video File Formats such as MPEG4, MKV, H.264 do not do this)

Sometimes, on some systems, TestUFO just doesn't work reliably. It does a best-effort VSYNC to the end user's native Hz in realtime. It works amazingly well for more than 90% of GPU-accelerated web browsers, but TestUFO can indeed fail.

For this reason, TestUFO has one of the most accurate stutter-detectors ever invented for a web browser which you can watch at www.testufo.com/animation-time-graph and it continuously compensates all animations to known jitter seen in the graphs, and then warns the users (with orange or red message) if fluidity violates accuracy.

Also, I piggyback on the local VSYNC as a method of scheduling the next refresh cycle's frame, so even if I am 100 microseconds 'early', I've rendered a frame that's accurate to a correctly scheduled VSYNC, allowing micrsecond-accurate software based BFI in a web browser animation. Occasionally, buggy browsers will often mess this up, but I also use heuristics (in JavaScript) to determine if this could have happened, like my color-coding of the spikes at www.testufo.com/animation-time-graph .... The end user simply sees a green READY whenever the animations are microsecond accurate and frame:refresh sync'd in realtime.

I had to concurrently stack multiple HTML5 APIs simultaneously to compensate for Meltdown/Spectre timer fuzz, but as long as I've confirmed I successfully linked a HTML5-render to a specific VSYNC of a specific Hz, I can be fairly confident (at least with Chrome, on a single-monitor Windows 10 system) of having achieved microsecond accuracy. This is because I have a lot of error margin (not much, but several milliseconds worth usually) to attempt to schedule a specific HTML5-JavaScript rendered frame to a display's specific VSYNC. It's not easy because there's no dedicated API but heuristically cross-referencing multiple HTML5 JavaScript calls concurrently, allows me to successfully determine display behavior it in a way approximately resembling a native DirectX API such as D3DKMTGetScanLine()

Video files and video players do not do this! Software BFI needs perfect frame:refresh sync.

Very few web animations has successfully achieved microsecond-accurate (for a few seconds) software based black frame insertion. It far exceeds the accuracy of video.

High speed videos confirm the microsecond-accuracy of many TestUFO tests. That's why TestUFO is now successfully part of some science papers -- it animates accurately enough to be scientifically trusted

Be noted, it is certainly quite possible that www.testufo.com/blackframes plays incorrectly in your browser on your specific system. I cannot rule that possible error margin out, but I can confirm that the software BFI effects often happen reliably at 60Hz and up in the majority of GPU-accelerated web browsers on Windows systems (as long as Windows doesn't force-disable GPU acceleration or disable desktop compositing, which consequently disables GPU acceleration). For this, try a different browser or a different computer, it will usually solve the problem.
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 10 Nov 2021, 13:31

Chief Blur Buster wrote:
10 Nov 2021, 12:34
Great OK. Yes, your respones have answered my first question of what is the cause of the double image effect. And if you think that my video are not valid, although I see the same at the recorded video than at your web. I don't have more question as they can't be answered as what is seen at the video could not be representative af the video frame secuence.

But maybe as I have explain the secuence of frames and editions I did at the video, you could say if you thing that it will cause the effects that the videos are shown.

Also maybe I could try to do the same tests but with your web code, I know some of html, javascript and PHP. But it will be difficult to me and it will take me a long time.

I have been writing this, while you have posted, to explain more my tests. As I said maybe the videos are not valid but the secuence of frames and the editions could be:

I have readed your posts again and this:
Chief Blur Buster wrote:
08 Nov 2021, 16:11

TestUFO double image animation creates the double image effect in pure software via this:
Sequence 1 of 4 = flash a frame
Sequence 2 of 4 = black frame
Sequence 3 of 4 = flash the same unchanged frame as sequence 1
Sequence 4 of 4 = black frame

Your eyes are analog and following the UFO in its vector. Your eyes are in a different position in Sequence 3 than in Sequence 1, so the identical frame (in same old pixel positions) are flashed in a different location of your retinas. So you get a double image during the eye-tracking situation.

For CRTs, they naturally flicker, so CRT 30fps at 60Hz looks like
Sequence 1 of 2 = flash a frame (CRT naturally flickers)
Sequence 2 of 2 = flash the same frame (CRT naturally flickers)

The constant is repeated flash of the same frame = duplicate image.
Answers this question I did:
mynm wrote:
06 Nov 2021, 15:38

But I have a question that I don't see is answered here. What is the technical explanation of this double image effect?.
Thank you very much for the explanation.

But do you think that what I say here could answer the question as well?:
mynm wrote:
07 Nov 2021, 15:05
Also my software record is not recording this image secuence for the 30 fps line of the ufo compare frame rate rest:

Sequence 1 of 4 = flash a frame
Sequence 2 of 4 = black frame
Sequence 3 of 4 = flash the same unchanged frame as sequence 1
Sequence 4 of 4 = black frame

What I see with the editor is this secuence:

Sequence 1 of 3 = flash a frame
Sequence 2 of 3 = flash the same unchanged frame as sequence 1
Sequence 3 of 3 = flash a frame

This is what I see at the record, it is only edited to get the inverted colors:

Image


About these post were you say that my videos are not valid:
Chief Blur Buster wrote:
08 Nov 2021, 16:18
Chief Blur Buster wrote:
08 Nov 2021, 16:49
I only can say that I have recorded the video with my AMD gpu driver software, if it is not recording the video well, that is I think that I can't know.

About that the page were I have uploaded the video, that is mega and not youtube, I can't know if is showing the video well or not.
But what I see is that the video I get with the video editor, is showing the same secuende of fps at MPC-HC, passing one by one the fps with ctrl +, and at the video editor. And that I see the same played images at MPC-HC and at the web page. But you can download the video if you see a problem with the web.


About this:
Chief Blur Buster wrote:
08 Nov 2021, 16:49

Color disortion artifact in one of your videos:
screen-record-1.png
Is not a distorsion artifact is what I have edited. That frame is from a 30 Hz video but I have a 60 Hz one. And what I have edited is this:

Image

At the 60 fps line, in one frame the ufo is red and at the next green.

At the 30 fps, in one frame the ufo is red, the second a black patch and the last a green ufo. Like I said here:
mynm wrote:
07 Nov 2021, 15:05
Chief Blur Buster wrote:
08 Nov 2021, 16:49

Vertical tearing distortion artifact in another one of your videos. This is ironclad proof of a VSYNC violation.
screen-record-2.png
This is also what I have edited:

Image

The video is showing the right half of the ufo, a full frame and then the right part of the of. But was wrongly done as may intention was that the full frame were the one were the ufo have not changed the possition, and is not allways it as it don't have enough frames I nedd three per cicle and I have two. Also I did a second video covering with a white patch the none repeated frame but is wrongly done as well.

I also have another video with this secuence:

Image

The video is showing half of the ufo per frame at the 60 fps line.


All of this is explained here:
mynm wrote:
08 Nov 2021, 15:09

The thinks is that I don't have an explanation for what is causing that the videos result are like that two frames are mixed to get one. Is like 60 fps and 60 Hz is like seen only 30 efective fps. But I don't know why and I don't see and explantion at your web and post of what can cause this. If I don't have a response here, I think I will don't have one at any other forum.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 10 Nov 2021, 13:52

mynm wrote:
10 Nov 2021, 13:31
Great OK.
Before we continue, I have to clarify one more thing.

I wonder if you're you're suggesting the use of capture (video, screen records, animated GIF, ete) as a post-analysis method, e.g. frame stepping videos of screen capture, rather than realtime demos. In this case, capture of any kind are a legitimate education tool for software-based BFI.

Software BFI videos done perfectly well can work if recorded and played back on the SAME system (e.g. your computer).

But they won't always work the same way when played on a different computer in a different country or OS or browser etc, because of the microsecond-accuracy problem which I've explained in some newer posts above. This is a big problem for online education and YouTube channels. That's why my question is very important before I reply to your question.

So before I reply, I need to ask:

(1) Are you using capture with the intent of worldwide real-time playback for real-time demo of software BFI worldwide?
(not recommended because of explanation here and here)

OR

(2) Are you using capture with the intent for single-frame-stepping or slow-motion operation?
(valid education tool for BFI, in parallel to other teaching techniques)

QUESTIONS:
-- Are you using capture because of (1) or because of (2)?
-- Who will be the audience of the BFI captures in the future?
......Will this be a general audience like a YouTuber channel?
......Or are you sharing BFI captures only with me only to ask questions?

Once I understand why we can't avoid .MP4 files (or any capture container format used for any form of recordings), I can answer you. I assume you re-read my new posts here and here, explaining why you can't insert realtime software BFI in a YouTube channel except for slow-mo explanations (non-realtime).

Once I understand why you're wanting to use captured recordings of any form for analyzing software BFI, I will try to reply with the correct contextual answer. We will waste less of each other's time this way.
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 10 Nov 2021, 16:25

Chief Blur Buster wrote:
10 Nov 2021, 13:52
mynm wrote:
10 Nov 2021, 13:31
Great OK.
Before we continue, I have to clarify one more thing.

I wonder if you're you're suggesting the use of capture (video, screen records, animated GIF, ete) as a post-analysis method, e.g. frame stepping videos of screen capture, rather than realtime demos. In this case, capture of any kind are a legitimate education tool for software-based BFI.

Software BFI videos done perfectly well can work if recorded and played back on the SAME system (e.g. your computer).

But they won't always work the same way when played on a different computer in a different country or OS or browser etc, because of the microsecond-accuracy problem which I've explained in some newer posts above. This is a big problem for online education and YouTube channels. That's why my question is very important before I reply to your question.

So before I reply, I need to ask:

(1) Are you using capture with the intent of worldwide real-time playback for real-time demo of software BFI worldwide?
(not recommended because of explanation here and here)

OR

(2) Are you using capture with the intent for single-frame-stepping or slow-motion operation?
(valid education tool for BFI, in parallel to other teaching techniques)

QUESTIONS:
-- Are you using capture because of (1) or because of (2)?
-- Who will be the audience of the BFI captures in the future?
......Will this be a general audience like a YouTuber channel?
......Or are you sharing BFI captures only with me only to ask questions?

Once I understand why we can't avoid .MP4 files (or any capture container format used for any form of recordings), I can answer you. I assume you re-read my new posts here and here, explaining why you can't insert realtime software BFI in a YouTube channel except for slow-mo explanations (non-realtime).

Once I understand why you're wanting to use captured recordings of any form for analyzing software BFI, I will try to reply with the correct contextual answer. We will waste less of each other's time this way.
I'm not going to use my video on youtube or for any audience. I only didn't have found an explanation on the internert of why the double image effect occur and what is the cuase of it. And now I have found an explantion for it here with your posts.

The video test are only test that I have done for trying to understand it. The conclusion I was getting from them are different of any thing I have readed about it. So that, I only want to know if my conclusions were correct, and if not, why the effects I see at the videos are happening.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 11 Nov 2021, 14:57

I have done one more video test, although you say that the video tests are not valid.

This test have impressed my :o. I have done a 60fps video with the ufo static and only changing the color from red to green form one frame to the next for one minute, to see if the frame color mix is the same at an static image as in a motion one. This is the edited video, is not a camera record is done with a video.

I have tested it at a CRT at 60hz and at a LCD at 60Hz. And the ufo color is static, is a dark red as a mix of bright red an the dark green.
And now the impressive effect I see is that, at the CRT, if you move your head like saying no, horizontally. I see the ufo two times at the red and the green color :shock:. I don't happens at the LCD.

I don't know how to explain this. Could it be maybe a retina-brain effect?, as I it couldn't be that my video or the player have an error. Why it happens at the CRT and not at the LCD?. If this doesn't seem relevant to you I don't know what could do it. Is like is as I said that two frames are mixed to get one. And I have been thinking that, strangely, this could explain all the effects you explain here with your test.

I think that you are the best person at the internet that could test this and say how this occur.

Edited: Think it better, I Suppose it is a nomal motion or strobe effect as the CRT is showing the two colors, and that at the LCD de lower responsse is mixin de colors as it can be changes bettewen frames. But I don't have readed about it, sorry I suppose that is some thing like that.
Last edited by mynm on 18 Nov 2021, 03:45, edited 2 times in total.

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