Comment by bob1029 | Hacker News Reader

Comment by bob1029 | Hacker News Reader

This stuff has been a nightmare for us for a long time. We have to scan pdf417 barcodes from physical identification as part of our offering.

Recently, we stumbled upon some cheap USB keyboard emulator 2d scanners that can pick these up very reliably. For our product/customers, this is a viable path. We have tested probably 30 different webcams by this point. The only 2 that are as reliable as the handheld CCD scanner are the iPad and my Canon DSLR tethered to my PC in automatic mode with a macro lens.

Resolution is a factor, but so is frame rate and environment. You have to consider the full UX stack. Someone is required to physically position the barcode in a particular way with certain lighting constraints, etc. With a handheld CCD scanner, you get a laser guide for precisely what distance to go for, and an ergonomic experience that is much more conducive to successful scans. Most offer on board illumination, so even in a pitch black room you will get a successful scan.

We ended up going with the purpose-built barcode sleds from Infinite Peripherals. The Linea Pro, I think. Extra battery, onboard illumination/laser guide, _really_ fast barcode engine in any orientation, and a few pretty simple SDK options. We ended up using "our custom webkit browser will fire a custom JS event on scan", which worked perfectly for our purposes.

Everything else is measurably slower: waiting for focus in a dim room, low framerate, weird other issues.

We use the Linea Pro too w/ the SwipeTrack browser making them available in our web app. We've previously used both the Infinite Peripherals SDK w/ an iOS app, but SwipeTrack have a pretty good JS API [1].

Funnily enough, the Linea Pros have been going down hill. They swapped out the barcode engine and it is not fast / crisp. Sometimes faster to just use the iOS Camera (w/ Swipetrack) instead of the Linear Pro's sled.

[1] https://files.littlebird.com.au/SwipeTrackBrowserAPI_200-Yre...

Wow, I don't like the sound of that at all. The version we're using is an older.... 5? 6? So it would predate those issues but that's literally.... half the point of the thing! Lightning fast barcode engine + range + extended battery + pistol grip!

The ones with miniUSB cables are good, the USB-C, not so much.

We also scan pdf417 from ID cards. In our case, it was much easier to just use hardware 2d scanners. We are a b2b SaaS and they are scanning IDs all day, so a hardware solution makes sense.

The weird thing about pdf417 is that there is a lot of helpful info our there, up until a point. It's like everyone is collaborative and asking/answering questions up until the point they really figure it out, but those last few steps never much make it into open code.

A couple times a year I go searching to see if anyone has implemented solid pdf417 in WASM yet. It seems like a natural fit to me, and I am sure people have done it, but I have yet to see anything publicly available.

What device are you using to scan? If you can use Android, Chrome supports pdf417.

I wonder how good the Chrome/Android PDF417 reader is? Is it just ZXing, or something else under the hood? For PDF417, ZXing is only OK. Unfortunately PDF417 is a pretty crappy format to decode with a sensor/camera compared to DataMatrix and QR which have much easier alignment targets and are designed for the sensor/frame based use case (instead of a 2D scanning laser). I wouldn't expect great performance out of BarcodeScanner / Android Chrome if it's just using Zebra Crossing under the hood.

Chrome is likely using ML Kit on Android under the hood on Android. [1]

Well if you try the demo I just made [2] you can find out. Works pretty well in Chrome Version 99.0.4844.51 (Official Build) (arm64) and on my Pixel 2. Naturally won't work on my iPhone because #SafariIsTheNewIE

[1] https://developers.google.com/ml-kit/vision/barcode-scanning...

[2] https://files.littlebird.com.au/barcode20.html

Here is how you can do it on Android: https://files.littlebird.com.au/barcode9.html

I used the microblink one for a small toy project and it worked well in all browsers.

https://demo.microblink.com/self-hosted-api/pdf417

I found the most reliable barcode scanner to be an old Symbol usb scanner.

I also found that I could scan barcodes off of a screen with a laser scanner if I put a translucent white plastic bag over the screen. Maybe someone with more knowledge about optics could give some insight into why that trick works. My understanding is that laser scanners should only be able to scan by reflection, and shouldn't work off of a screen at all.

Note that they’re scanning 2D “pdf417” barcodes.

Reading a linear barcode is quite easy, the shitty webcam of my 2010 macbook pro was enough for Delicious Library to pick most every article instantly, usually faster than I could even present the article.

Purpose built barcode scanners typically don’t fumble with autofocus have faster 0-latency autoexposure (adjusted during frame readout) and even the good 2D CMOS sensor ones will start decoding linear or stacked codes such as PDF417 while the frame is being transferred. That can’t be beaten for latency.

Idk but whatever library the NHS website is using to scan the QR codes on LFTs is flawless, as soon as the camera view opens it immediately scans, you'd miss it if you blinked.

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