compression.md

-Transparent stream compression is always optional. Compressed data is recognized by the four-byte magic value `1 76 79 66`.
+Compressed data is recognized by the four-byte magic value `1 76 79 66`.
 
 ```c
 struct {
@@ -13,6 +13,9 @@ struct {
 };
 ```
 
+Besides the [`Layouts.amb`](Amberfiles/Layouts) items, file/stream compression is transparent and optional.  
+
+
 Stream format
 =============