Media constraints are the #1 reason it won't scan in my experience. You need at least ~1000px horizontal to reliably decode PDF417. If the resolution is 720p or lower, you aren't capturing enough information for a decode.
Scanning 2D barcodes only works reliable on smartphones with good camera and with good lighting.
I needed it for a ticket scanner used on an old phone at night entries for concerts.
Went and bought a hardware scanner (for 30€ or something) that connects itself as a "Bluetooth keyboard". Works like a charm.
We wont even fully certify iPhones for use with this solution because we have seen consistent failure to autofocus on the barcode for "some weird reason". iPads work like magic though. I have to go out of my way to not get a quick scan on recent generation iPad camera.
We went down the hardware scanning path w/ keyboard emulation in the browser, but its kind of clunky when you are considering the overall solution stack in a B2B setting.
> Editors:
> Miguel Casas-Sanchez (Google LLC)
> Reilly Grant (Google LLC)
> Status of this document
> This specification was published by the Web Platform Incubator Community Group. It is not a W3C Standard nor is it on the W3C Standards Track.
Which JS library do you use?
I couldn't find a single library that can reliably scan PDF417 barcodes.