Embedded Gain Maps Missing in AVIFs?

[blue-j]

Adobe has released their Gain Map specification and provided sample files, a spec, and an app for reading.  ExifTool already supports the metadata, but I am puzzled about the lack of embedded binary data in the AVIF samples.  ExifTool sees the embedded gain maps in JXLs and JPEGs fine.  For AVIF, we do have the QuickTime Auxiliary Image Type urn:com:photo:aux:hdrgainmap listed, but... no aux image.

Is there such a binary object in them?  I've attached 5 of the sample files from Adobe for review.

https://helpx.adobe.com/camera-raw/using/gain-map.html

- J

[Phil Harvey]

I don't have time to look at these now, but it is likely that the gain maps are compressed image data, which ExifTool doesn't extract (they aren't a stand-alone format, so not very useful to most people).

- Phil