parityOf
How faithfully an effect will be previewed, with no work at all.
The answer depends on the export backend that is registered, because parity is a property of the pipeline that renders an effect rather than of the effect. The same id can be EffectParity.Exact on one backend and unrenderable on another, so this returns what the registered engine says and nothing when there is no engine to ask.
Parity is also readable from an ExportPlan once an edit has been planned, and from a player's live preview info.
Return
The effect's parity, or null when the registered engine does not know specId, cannot render it, or no export backend is registered at all. Call plan for the reason, which is the only place that distinguishes the three.
Parameters
The id of the effect spec to look up.