ReadonlychannelsReadonlydataByte offset of the first sample — walked, never this writer's own constant.
ReadonlydeclaredWhat the header (or ds64) CLAIMS the data chunk holds, in bytes.
ReadonlyframesPer-channel frames the law gives — readable audio, never a count off the end of the file.
ReadonlyplatterWhat is actually after dataOffset, MEASURED: fileBytes - dataOffset.
ReadonlyrateReadonlyunsealedWhether the header cannot be believed — it claims more audio than is there, or it was never patched at all. DERIVED from the file, never stored (R-049): the sidecar carries no seal flag because a stored one goes stale the instant the recorder seals the header.
What a reader needs to know about a track file before it can read a frame of it.