We need a definition of 'frame'

[ProgramMax]

A definition of 'frame' should probably be in https://w3c.github.io/PNG-spec/#apng-frame-based-animation.

This came up in #284 where <!-- need a definition of frame --> was added to the doc.

[svgeesus]

Agree, we do. The description needs to be somewhat nuanced because we need to have a definition that covers:

1. A static PNG
2. An animated PNG where the static image is the first frame
3. An animated PNG where the static image does not form part of the frame-based sequence

We do have some wording in cLLi about this:

For static PNG, the static image is analyzed and is considered to be the first (and only) frame. For animated PNG, each frame of the frame-based animation sequence is analyzed.

If we have a definition of frame, that could be simplified to

Each <a>frame</a> is analyzed.

[svgeesus]

Would be fixed by PR #305