Showing posts from July, 2020

piLagTesterPRO engineering sample availalbe

The piLagTesterPRO measures input lag and response time using a raspberry pi to generate the signals, and  the hardware/software I've designed to measure the time-course of those signals on your display. I built it for myself first and foremost but there's been some interest in offering for sale. I'm happy to oblige as long as you understand that this is not a pretty, mass market device, though it is quite functional and in fact offers quite a lot more features than the commercial options (leo bodnar and the time sleuth).

The hardware electronics design is finished, but I'm calling it an engineering sample because the packaging might evolve a little with your feedback.

Here it is, attached to its preferred (for the moment anyway) pi: the pi zero. Yes, that's tape. I consider this a good thing; if you want to configure it into another physical package it's very easy to disassemble. It might not be much to look at splayed on the carpet, but here's the good stuff:

this photo of it in action show the real time plotting of the monitor's lag, response time,  and back-light properties.

Let's see a few more details of the physical device. Here's how it plugs into the pi. With a "handy" guide as to which GPIO pins to plug it into. That's all the assembly that's really required.

There could be additional assembly if you want a fancy box for the light sensor. Personally, I decided to lean into the tape choice and use tape to attach it to the TV. This is actually really great, as it makes it very easy to monitor lag while you mess around with TV settings. Since the tape is on the bezel, there's no issue with messing up the screen. Of course, this mounting choice is up to you, and you'll have to provide your own tape anyway, since the painter's tape is only good for 10-20 removals before it looses adhesion.

Another option is to stash the sensor inside a box or bottle and hold it up to the screen:

It's really up to you, and if you come up with something extra clever do let me know. The sensor is somewhat directional, but the signal amplification is strong enough that you don't to point it exactly normal to the display surface so there's lots of room to play around.

piLagTesterPRO status update: Pi4 or nothing? Maybe not.

The piLagTesterPRO is an add-on for the Raspberry Pi that measures your display's input lag and response time with real-time graphs of what the monitor is doing.

There have been some significant delays producing a shippable version but the tl;dr is that I have a finished lag tester that's ready to be used by the outside world!

There have been two setbacks: first a critical component ordered from china almost 2 months ago is lost in the mail (assuming it was ever really sent). I have recently found a second but much more expensive US source, so that's not holding me back, though it does lessen my enthusiasm for purchasing more parts for a more professional build for this device, especially given no concrete measure of demand (read: how much to order).

2nd, the PI4 turns out to be a bit of a work in progress despite having been out for essentially a year. There are probably lots of great things about it, and certainly I've really appreciated how much faster my code compiles. But the video output on the device is plagued by issues with poor drivers. Luckily these are under active development. Unluckily, there are two drivers and the one I've been using until now is not their primary focus going forward.

I'm sure the driver(s) issue(s) will be resolved with the Pi4, but I'm tired of waiting for official firmware builds to see if it's finally good enough.  In fact, it's 99% of the way there - I have lag test code now that works fine on both firmwares about 99% of the time. But that 1% results in incorrect measures of lag. I can filter them out on my own hardware but I'm not confident enough that it will work on all resolutions and refresh rates supported by the PI4 to want to advertise Pi4 support just yet. Also, the current firmware doesn't support interlaced resolutions so you couldn't test 480i with a Pi4.

However, I'm willing to sell the piLagTesterPRO to anybody who wishes to use it on earlier versions of the PI. Everything but the PI4 uses the same video chipset. That means every pi that doesn't have a 4 in it's name should work, and even the Pi Zero (only $5!) works great with the piLagTesterPRO, despite being the slowest Pi you can buy. And when the Pi4 video drivers finally work right, I'll send you a free upgrade.

And if you happen to have both an older Pi and a Pi4 I'd be very interested in working with you to test if the piLagTesterPRO works at higher resolutions and refresh rates.

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