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Comment by rany_ | Hacker News Reader

The image is actually HEIF not AVIF :)

HEIF is just the usual container for AVIF encoded data, similar to how AV1 encoded data might commonly be in an MP4 or MKV container. HEIF might easily get conflated with HEIC, which is Apple's implementation of HEIF specifically for HEVC encoded data. Too many damn "HE"s, if you ask me.

If you run "strings" you should see "av01Image" pretty early on in the HEIF header, which is what signals it's really an AVIF file. Tools like "file" may possibly not be updated to look for that yet, so could just report the container alone.

To be fair I did lazily do:

         else if (c.slice(4, 4+4) == "ftyp") f="avif";

Because I didn't feel like parsing the HEIF to check it's actually AVIF. I'm pretty sure browsers aren't that bothered about the file extension or MIME type for images.

Huh, my image viewer claimed it's HEIC specifically. My camera also seems to conflate HEIC and HEIF in the settings. It provides HEIF as a format option, when I guess it should be specifying which codec is actually being used. I had no idea HEIF isn't tied to just HEIC though.

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