HEIF vs AVIF detection

[novomesk]

There is following code in qheifhandler.cpp

    if (w1 != "ftyp") {
        // not an ftyp box
        return Format::None;
    }

    // brand follows box name, determines format
    if (w2 == "mif1") {
        return Format::Heif;

Unfortunately ftyp+mif1 is used by AVIF too (examples here: http://download.opencontent.netflix.com/?prefix=AV1/Chimera/AVIF/ ) but qt-heif-image-plugin with older libheif are not able to load AVIF.

I saw situation when qt-heif-image-plugin is installed together with my qt-avif-image-plugin. qt-heif-image-plugin indicated that it can read the AVIF file (and as consequence the file was not opened via qt-avif-image-plugin) but qt-heif-image-plugin did not open it so the AVIF image was not displayed at all.

I think both qt-heif-image-plugin and qt-avif-image-plugin should read more than 12 bytes from beginning to determine file format, so we properly detect whether we have HEIF with HEVC compression or AVIF with AV1 compression.

[jakar]

Thanks for reporting this. This is clearly a bug.

It was commented here that maybe it would be better to use libheif to check this header info, but I haven't had a chance to look into that yet.

[novomesk]

Just a note: Future versions of libheif will support AVIF, so you will be able to load AVIF files via qt-heif-image-plugin too. But some distributions keep old versions of libraries. Letting libheif to auto-detect by itself what it is able to open is a good idea.

[salehqt]

Just added a pull request #22 to add complete support for AVIF to this plug-in. I hope this resolves this issue.