@lovell can I ping you for a second opinion on this?

(Dirk, who wrote libheif, would be the authoritative expert, but I'm hesitant to bother him directly. You could maybe open an issue on libheif and ask for clarification, or perhaps look for past issues which have discussed this)

@StefanOltmann Does your question relate to a specific patent? Perhaps https://patents.google.com/patent/WO2016193543A1 held by Nokia?

I'm uncertain about the patent situation surrounding HEIC.

If I had a comprehensive list of patents related to the HEIC container format, I could determine whether creating new containers or modifying existing ones would comply with applicable laws. While it's well-known that HEIC is heavily patented, I currently lack an overview of the specific patents that might protect it.

In discussions around this topic in the Exiv2 issues, Jon Sneyers mentioned that it should be safe to use ISOBMFF as specified historically, as it’s old enough that any relevant patents are likely expired. This reasoning is why I added generic ISOBMFF support to my library, specifically for reading files.

For reference, here’s a detailed answer he gave:
libjxl/libjxl#3236 (comment)

However, when it comes to manipulating or generating new HEIC files, I’m unsure if this would require a license.

Mainly because I would write boxes like "irot" and "ispe" that are defined in the HEIC specification. I don't worry about anything that was taken from the original ISOBMFF as is.

The key question is: Can we safely manipulate the container of a HEIC file, provided we don’t encode or decode the actual media bytes? Specifically, I’m curious if it’s permissible to include new thumbnail bytes in HEIC and AVIF files.

If working with HEIC containers is not legally safe, would AVIF be permissible? Both formats are similar in their use of the container, so clarity on this aspect is crucial.

The short/expensive answer is that you probably need a patent lawyer.

My non-lawyer interpretation of claims relating to HEIF the container is that they can mostly be ignored.

To pick an example, I attempted to search for patents that relate to HEIF the container where a claim is made on irot. The only patent I can find is https://patents.google.com/patent/US11985302B2 filed by Canon (and not Nokia) and the list of claims includes:

6. The method of claim 5, wherein the property box indicating the decoder configuration of the one or more images is a box with box type ‘hvcC’.

...which limits its application to HEVC-encoded images.

Perhaps it might be worth using https://patents.stackexchange.com/ to collate prior art on patent claims known to relate to HEIF the container.

(Please note that what is written above relates only to containers, and does not relate to codecs.)