Static kVTDecompressionPropertyKey_SuggestedQualityOfServiceTiers 

pub unsafe static kVTDecompressionPropertyKey_SuggestedQualityOfServiceTiers: &'static CFString

Available on crate feature VTDecompressionProperties only.

Suggests how quality-of-service may be lowered in order to maintain realtime playback.

This is an optional property for video decoders to implement. This property value is an array containing either CFDictionaries of property key/value pairs, or the array can contain special key values like kVTDecompressionProperty_TemporalLevelLimit. The first entry in the array should contain the set of properties that restore the default (full) quality of service; later entries should contain property sets with decreasing qualities of service. Clients may work their way down these tiers until they are able to keep up with the frame rate.

See also Apple’s documentation