For some IFF based file formats (AIFF / WAVE / DSDIFF) there are frequently files that omit trailing null bytes. That means the container sizes inside the file report a larger overall size then the actual file size.

As long as this is just null bytes this behavior makes sense, and it seems to be quite common. But the current mutagen implementation assumes that a file needs to be at least the size to fit the size reported by the outermost container and fails when writing such truncated files.

See also:

• https://github.com/quodlibet/mutagen/pull/515

• https://community.metabrainz.org/t/receiving-valueerror-when-saving-some-files/502884