RIFF 全体
+------+-------+------+---------+---------+---------+
| RIFF | sizeF | sfbk | LIST ...| LIST ...| LIST ...|
+------+-------+------+---------+---------+---------+
- 4B -><- 4B -><- 4B->
<--- sizeF -------------------------->
sfbk 以降
INFO-list
+------+-------+------+---------+---------+---------+
| LIST | sizeL | INFO | <chunk> | <chunk> | ... |
+------+-------+------+---------+---------+---------+
<--- sizeL -------------------------->
sdta-list
+------+-------+------+---------+---------+---------+
| LIST | sizeL | sdta | <chunk> | <chunk> | ... |
+------+-------+------+---------+---------+---------+
<--- sizeL -------------------------->
pdta-list
+------+-------+------+---------+---------+---------+
| LIST | sizeL | pdta | <chunk> | <chunk> | ... |
+------+-------+------+---------+---------+---------+
<--- sizeL -------------------------->