@1div0 helped with the testing. In particular, he gave me access to his .avif files taken with a Pentax camera for which Exif.Image.Maker is Ricoh.
@1div0 did some great work on the code, however I didn’t accept his changes because, in the event of legal trouble, I don’t want to drag anybody else into the horrors of litigation. All the text and code in my book is my work, albeit influenced by many other folks.
I am not afraid of the legal situation concerning ISOBMFF and my book. I can’t imagine Canon, Apple, Pentax, or Ricoh taking legal action against a retired Engineer in England for publishing a book about reading unencrypted metadata from a file formatted using a public standard. They would have to prove loss. The book is a free download, so I have not profited.
There’s another point about this. To take legal action against open-source developers and users for reading data in their own files, is so “20th Century”. The world has moved on from those bad old days.