Replace legacy libusbx depends with libusb in makedepends.
Add (required) qt5-multimedia to depends.
Switch to git sources, as release 1.4.1 fails during linking and backporting patches is super nontrivial.
Add pkgver() function to retrieve sane version string.
Add all available sodeps in package() and the respective packages to makedepends.
Update contributor info.

FTR, commands used to change arch=() and then verify the changes:

$ sed -Ei "/^arch=/{s/ *?['\"]?i686['\"]? *?//;s/ *$//}" */*/PKGBUILD*

$ grep -r i686 * | grep arch= | grep -v repos

$ svn diff | grep -A 1 ^-[^-] | grep -v -- -- | cut -c2- |
  while IFS=$'\n' read -r l1; IFS=$'\n' read -r l2; do
    echo "$l1 -> $l2"
  done | sort -u