We say that pict indicates that there is no claim for timing conformance, and add that an edit list that selects 0 or 1 images from the sequence documents that there is no time-based playout behavior.
m35042 Auxiliary Image Sequence Tracks in 23008-12
Perhaps the URN box and track reference should be in part 12. For now we put these in the image file format, clearly in two sections (one generic, one HEVC specific). ‘File readers…’ should probably be phrased in the passive “X is recommended”.
