This issue was first reported in Chromium issue 1246678.

If an AVIF image encoded by cavif has an alpha plane, the alpha image item in the AVIF image does not have an ispe property. This is not standards-compliant.

HEIF (ISO/IEC 23008-12:2017) Section 6.5.3.1 says the ispe property is mandatory (per item). See page 11.

MIAF (ISO/IEC 23000-22) Section 7.3.6.3 (Image spatial extents) reiterates that:

ISO/IEC 23008-12 requires that every image item be associated with a property of this type.

See page 15.

no decreasing in file size after changing resolution of avif image

First of all, thank you for all of your amazing image work!

It looks like Chrome 91 (current beta) is requiring extra format compatibility for AVIF files. Images generated by cavif that work fine in the current Chrome stable will stop working down the road.

See e.g. https://bugs.chromium.org/p/chromium/issues/detail?id=1198455&q=avif&can=2

Running an example cavif-generated image through the AOM AVIF Validator turns up the following issues:

• [miaf][Rule #1] Error: The HandlerBox shall be the first contained box within the MetaBox
• [miaf][Rule #2] Error: compatible_brands list shall contain 'miaf' (not found) and 'mif1' (found)
• [miaf][Rule #4] Error: 'hdlr' not found in MetaBox
• [miaf][Rule #24] Error: Found no 'pixi' associated for 1 displayable (not hidden) images (ItemIds={1})

(I believe it is primarily the lack of "pixies" Chrome is upset about. 😄)

I'm guessing this library (rather than ravif) is where fixes would be needed, but am unsure.