Accept AVIF lsel property with layer_id 0xffff#453
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Currently any lsel (LayerSelectorProperty) is treated as an unsupported essential property, so its item is forbidden and consumers reject the whole image. A layer_id of 0xffff, however, does not select a specific spatial layer. It only enables (without requiring) progressive rendering: a client may render progressively or just show the final image, which is also what ignoring the property does, so no client can get it wrong. Such a property therefore should not make the item unsupported. Parse the lsel layer_id (previously the box was skipped) and, when it is 0xffff, accept the item and don't report lsel as an unsupported feature. Other layer_id values remain unsupported as before, and the requirement that lsel be marked essential is still enforced for all layer_id values. Adds a test and fixture (tests/lsel-layer-id-ffff.avif, a green image carrying an essential lsel with layer_id 0xffff). See https://aomediacodec.github.io/av1-avif/#layer-selector-property
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Currently any
lsel(LayerSelectorProperty) is treated as an unsupportedessential property, so its item is forbidden and consumers reject the whole
image.
A
layer_idof0xffff, however, does not select a specific spatial layer. Itonly enables (without requiring) progressive rendering: a client may render
progressively or just show the final image — which is also what ignoring the
property does — so no client can get it wrong. Such a property therefore should
not make the item unsupported.
This parses the
lsellayer_id(previously the box was skipped) and, when itis
0xffff, accepts the item and does not reportlselas an unsupportedfeature. Other
layer_idvalues remain unsupported as before, and therequirement that
lselbe marked essential is still enforced for alllayer_idvalues.Adds
public_avif_lsel_no_layer_selectionand a fixture(
tests/lsel-layer-id-ffff.avif, a green image carrying an essentiallselwith
layer_id0xffff).Spec: https://aomediacodec.github.io/av1-avif/#layer-selector-property
Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=2055634