[Feature Request] Support encoding thumbnail image

[macdavis]

It would be nice if the user can also set the thumbnail dimensions (either height or width). Thanks for considering!

[y-guyon]

Thank you for your interest in AVIF.

Could you share more details about your thumbnail use case? For example:

• Wanted thumbnail dimensions
• Maximum file size increase (in bytes and/or percent)
• Target application(s) or environment(s): OS, device etc.
• Why do you need an embedded thmb item rather than a separate file (with a higher-level reference to the original asset)?
• Why do you need an explicit thmb item rather than letting the application generate and cache a preview image?
• Could/should it be animated if the original asset is an image sequence?
• Could/should it be HDR or 12-bit or transparent if the original asset is?
• Could/should it keep the original asset width/height ratio?
• Could the thmb be a layer or frame in the primary item or track, or does it have to be a separate independent elementary stream?

[macdavis]

Please see below for details.

Wanted thumbnail dimensions

Ideally leave it to the user to define, similar to libheif, making arbitrary width/height (whichever is larger) as an input and keep the original ratio.

Maximum file size increase (in bytes and/or percent)

To be discussed? Personally I am not sensitive to file size.

Target application(s) or environment(s): OS, device etc.

iOS/MacOS

Why do you need an embedded thmb item rather than a separate file (with a higher-level reference to the original asset)?
Why do you need an explicit thmb item rather than letting the application generate and cache a preview image?

As per the discussion in #2941

Could/should it be animated if the original asset is an image sequence?

Maybe can implement still image first?

Could/should it be HDR or 12-bit or transparent if the original asset is?

Yes, HDR or 12-bit or transparent if the original asset is

Could/should it keep the original asset width/height ratio?

Yes

Could the thmb be a layer or frame in the primary item or track, or does it have to be a separate independent elementary stream?

Prefer being a separate independent elementary stream