_WRITE_GROUP</td><td>Current family 1 group while writing.  Currently
    used only when writing QuickTime tracks.</td></tr>

<tr><td>DEL_GROUP</td><td>Hash of groups to delete.  Value is 1 to delete group
    completely, or 2 if tags were added back after deleting the group.  May
    have a leading "-" if excluded from a delete.</td></tr>

<tr><td>DEL_PREVIEW</td><td>Flag to delete preview from after JPEG EOI</td></tr>

<tr><td>DemoteErrors</td><td>Errors are demoted to warnings and this count is
    incre