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Showing posts from June, 2020

Enable root login on Raspberry Pi & create MS DOS for the 21st century!

I use my Raspberry Pi like a MS-DOS computer for 21st century, so of course I want to run as root - and login that way too. It's easy:

Give root a password:

sudo passwd root

enable login as root:

sudo nano /etc/ssh/sshd_config

find (ctrl-w): #PermitRootLogin prohibit-password

make it look like

PermitRootLogin yes

then restart ssh:

sudo service ssh restart

Of course it's dangerous to run as root, but if you want to access hardware directly it's the only way to go. You might think about setting up a trashcan alternative to rm since you can get yourself into a lot of trouble with those two letters plus a typo or to.  Add this to the end of your .bashrc

alias emptyTrash='ls ~/.trashcan; du -sh ~/.trashcan; rm ~/.trashcan/* -rf'
del () { du -sh $*; mv $* ~/.trashcan/; }
[[ $- == *i* ]] && du -sh ~/.trashcan

and then in your home folder, do this once:

mkdir .trahscan

also why not autologin as root on the console?

First, use raspi-config to enable autologin for the pi user, then fix it to use root instead:

 nano /etc/systemd/system/getty@tty1.service.d/autologin.conf

give yourself a line line this:

ExecStart=-/sbin/agetty --autologin root --noclear %I $TERM

piLagTesterPRO input lag test result database

This database shows display input lag and response time (in ms) measured using the pi Input Lag Tester PRO. Since other databases only show input lag it was necessary to start Yet Another DB. Please email me (form below) if you have data to contribute.
Values in red denote average measurements for TVs that have inconsistent lag; between power cycles the lag will vary significantly (typically +/-8ms)

A quick definition of terms:

Native min lag is the average amount of lag (in ms) between sending the video frame over HDMI and the start of the monitor response at the upper edge of the screen (the threshold for "response" is 5% of a complete response) at the panel's native resolution. IE it does not include response time.

Response time is how long it takes a pixel to go from 0 (black) to 80% of full intensity (perceptually, nearly white).

Scan out is how long it takes for the display to draw from the top to the bottom of the screen. You might expect this to be 1/60=16.6ms but some displays draw much faster once they finally get started.

Real Lag is how long it takes for the entire frame of video to be rendered from top to bottom of the screen; it is the sum of the min lag, response time, and scan out.

In addition to the summary stats, full measurements are also included further to the right in the spreadsheet:
top 1st = minimum lag
top full = top 1st + response time
bottom 1st = top 1st + scanout
bottom full = real lag

There are other lag databases, but none that report response time and scan out, or summarize the real lag for each resolution. But, other database's are much larger.  I like the one from retroRGB which allows you to submit your own values. To compare between databases you want to use the "top, 1st" value reported here.

Dell U2410 deinterlacing and input lag review using piLagTesterPRO

This 1920x1200 LCD offers deep color, IPS, and component inputs in addition to HDMI, DVI, & DP.

Image quality

At 1200p it's bright, sharp, and colorful. Almost too colorful; in deep color mode (and game mode) it's supersaturated, with eye-searing reds.  It has no black crush, no croping and no aliasing. 720p is also close to pixel perfect, with no cropping or aliasing, though I think pixels might not be exactly square.

In 480p it's stretched to fill the screen, and blurry, but no aliasing errors. 480i clearly uses a different signal path, with massive oversharpening applied to the blur, and some cropping.  I did not test the component inputs but the deinterlacing for 480i over HDMI was really ugly so I have little hope for it. Ugly as in false colors/halos around text and such.

Input lag measured with a piLagTesterPRO

This display has a game mode, so I tested that in addition to sRGB mode (yes, color mode and speed cannot be set separately). I used a piLagTesterPRO to measure input lag. This device sends a frame of video over HDMI and measures how long it takes to display it. I report two kinds of values. The minimum lag is the earliest point any change is detected at the top of the screen. This overly optimistic value doesn't tell you how long it takes to see anything useful, but matches what other reviewers use. I also report a more realistic measure of lag: when the display has reached 80% of full brightness at the bottom of the screen. This combines both input lag and response time, and is closer to what you would actually experience in a game.



Display modemin lag480i real480p real720p real1080p realresponse timescanout
U2410 sRGB20.562.44543.143.16.1316.13
U2410 Game Mode4.062.228.326.526.56.0016.20

To summarize, in sRGB it takes 20.5 ms to start drawing the frame, and full brightness response time adds 6.1ms. This plus the scanout gives us the real lag to finish the entire frame: 43ms. Deinterlacing adds 17.4ms. Upscaling (or downscaling) does not appear to change the lag, except perhaps at 480p/i. Even by current standards this display is decent for progressive content.

Switching to game mode the performance is quite impressive: 4ms lag to start rendering the frame, and 26.5ms to finish the whole frame. Except in the 480i mode where it makes no difference.

Or, if you like to see the raw numbers:

Display480i top 1st480i top full480i bot 1st480p top 1st480p top full480p bot 1st720p top 1st720p top full720p bot 1st1080p top 1st1080p top full1080p bot 1st
sRGB39.845.75622.428.338.620.726.636.720.526.336.7
Game Mode39.945.7565.911.722.149.720.249.720.2


This set is interesting because it is well enough known to have been tested for lag by other sources than myself.  tftCentral measured it vs a CRT using a high speed camera, and reported 33.8ms (sRGB) and 14.4ms (game) of lag. Though they used to explain their method in detail the link is dead, but as I recall it was a digital stopwatch centered on the screen, which should correspond nicely to what people would perceive as lag, since the frame has to "develop" enough to have the numbers readable. I will use my "real lag" measure, minus 1/2 the scanout, which gives 35ms (sRGB) and 18.5ms (game), which I think nicely validates these values as measuring the perceivable lag of the display. 

Sony KDL-40VL130 HDTV: input lag / upscaling /deinterlacing review using piLagTesterPRO

This 1080P TV dates back to 2007, with 2 component inputs +  2 HDMI, along with other inputs less useful for retro gamers. It's not a smart TV but it sure is cheap on the used market.

Image quality

Native resolution is 1080p. It's bright, sharp, and colorful. It has no black crush, no croping and no aliasing. 720p is also close to pixel perfect, with no cropping or aliasing, though I think pixels might not be exactly square.

You can set 480p/i to be stretched to wide screen or maintain aspect ratio. Either way there's some cropping, about 10 pixels on each side. The up-scaling is bury, but uniform with no aliasing errors.

Input lag measured with a PiLagTesterPro

This TV has a game mode, and I used it exclusively for these tests, which were all over HDMI. I used a piLagTesterPRO to measure input lag. This device sends a frame of video over HDMI and measures how long it takes to display it. For each resolution I report two values, the first being the earliest point any change is detected at the top of the screen. This overly optimistic value doesn't tell you how long it takes to see anything useful, but matches what other reviewers use. I also report a more realistic measure of lag: when the display has reached 80% of full brightness at the bottom of the screen. This combines both input lag and response time, and is closer to what you would actually experience in a game.

Input Lag and response time
Resolution Optimistic lag
(top, 5% bright)
Realistic lag
(bottom, 80% bright)
480i 41.3 ms 66.3 ms
480p 23.5 ms 49.3 ms
720p 22.8 ms 47.3 ms
1080p 23.2 ms 47.3 ms


To summarize, the TV's input lag is 23 ms, and full brightness response time adds 9.5ms. Deinterlacing adds 18ms. Upscaling (or downscaling) does not appear to change the lag. Even by current standards this TV is decent for progressive content. For interlaced content the lag is measurable, but at the trade-off of looking very good.

Without the remote

This has decently usable controls without the remote.

Other similar models

I would expect that the 46LV130 would perform about the same as the 40VL130 , based on the model numbers, and a quick skim of the specs (both are native 1080p displays). But I only tested the 40VL130. A forum post said this was a costco only model number, and is the same as the 40V3000, but I don't think this is true: the input back panel looks different. Based on the back panel it might be a KDL-40V2500 though. It appears to have retailed for between $2000 and  $2500.

Sony KDL 40s20L1 input lag, interlacing and upscaling review

This 720p TV from 2006 has 1 HDMI and 2 YPbPr inputs.

I used a piLagTesterPRO to measure input lag. This device flashes a white probe box against a black background and measures how long it takes to display it. For each resolution I report two values, the first being the earliest point any change is detected at the top of the screen. This overly optimistic value doesn't tell you how long it takes to see anything useful, but matches what other reviewers use. 2nd I report when the probe has reached 80% of full brightness at the bottom of the screen. I call this "realistic lag", and it combines both input lag and response time, and is closer to what you would actually experience.

This TV does not have a game mode, though it does allow you to select titles for each input, one of which is "game". This does not change the lag.


Input Lag and response time
Resolution Optimistic lag
(top, 5% bright)
Realistic lag
(bottom, 80% bright)
480i 66.8ms 93.6ms
480p 49.6ms 77.5ms
720p 49.6ms 77.3ms

To summarize, the TV's input lag is 49ms, and full brightness response time adds 13.5ms. Deinterlacing adds 17ms. Upscaling/downscaling does not add any lag. For retro gamer, 90ms of lag is too much so I didn't continue my investigation further.

Update:  on a lark I tried an adapter that lets my pi output video over yPrPb, and found that this actually reduced all lag measurements by about 9ms!  EG measured at the top the 480p optimistic lag went from 49ms to 38ms, and the Realistic lag from 77ms to  67ms.  Shocking. For some reason the analog signal pathway is faster.  I also tested 480i which gave an optimistic lag of 55ms and a Realistic lag of 82ms. Still too slow, but an improvement! 

I found the same result if I plugged into the VGA input (VGA was picky about what resolutions it would take; it worked with native 1360x768 though, with pixel perfect output).

Clipping

All modes clipped some of the input off, usually from the left and right edges.

Upscaling

All resolutions, including native 720p, had aliasing artifacts. There is no pixel-perfect option. Combined with the poor lag+response time this is a bad TV for any type of gamer, retro or modern.

Compared to other TVs

computed (ms)
DisplayYear made (TV?)Native Resnative min lagnative real lag480i real lag480p real lag720p real lag1080p real lagnative response timenative scan out
Dell E198FPb20081024p2.720.439.035.05.0012.70
Vizio VO370M20101080p2.523.683.049.047.024.35.4715.67
Dell U2410 (game)20101080p4.026.262.228.326.526.56.0016.20
AOC/Envision G19LWK2010900p3.131.239.538.738.437.815.5012.60
Dell E2211H20141080p3.033.634.734.534.133.815.0015.57
Panasonic TH-58PE75U2008720p28.034.034.034.034.034.06.000.00
Dell 1907FPc20081024p3.034.035.934.815.0016.00
Corprit D157 (hdmi)20211080p3.134.534.934.834.633.916.2515.13
Samsung S27C23020141080p2.936.136.636.137.018.2514.97
Vizio E470VL (vga)20111080p22.039.039.039.039.09.008.00
Dell U2410 (sRGB)20101080p20.542.862.445.043.143.16.1316.13
RCA L40FHD4120101080p20.346.665.048.047.046.09.6816.63
Sony 40VL130 (game)20081080p22.847.366.349.047.347.39.0815.43
Polaroid FLM-373B2007720p28.049.082.049.049.049.07.0014.00
Philips 42PFL3603D/F720091080p29.050.084.050.050.050.05.0016.00
Emprex HD 32022007720p27.050.5126.051.050.08.5015.00
LG 42LC2D2006720p28.350.654.650.850.46.3015.95
GPX TDE3245W2016720p28.051.0102.051.051.051.08.0015.00
Sony KDL-46EX40020101080p28.052.087.052.052.052.08.0016.00
Toshiba 40L2200U20141080p30.056.074.056.056.056.010.0016.00
Vizio VO22L FHDTV10A2008720p28.061.094.061.061.061.018.0015.00
Sharp LC-C3234U2009720p33.064.683.666.664.615.0016.60
Toshiba 46L5200U20131080p55.071.089.076.071.074.08.008.00
Sony 40S20L12007720p48.472.090.172.973.49.6014.00
Samsung HP-T425420111080p69.775.794.176.075.75.001.00
LG 47LW6500-UA20121080p66.680.7149.7149.081.780.92.2711.83
Vizio E470VL (hdmi)20111080p69.086.0128.095.095.086.09.008.00

It's not very good, near the bottom of the list unfortunately. Even if the results were based on the VGA/yPbPr input it wouldn't be much higher on the list. 

Other models

I tested the 40s20L1, but judging from manuals and release dates the hardware for the 32s20L1 would probably be the same, and would be expected to perform identically.

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