diff --git a/readme.md b/readme.md
index 5185eff..fd5456f 100644
--- a/readme.md
+++ b/readme.md
@@ -53,6 +53,11 @@ $defs:
   GWRadioURI:
     type: uri
     description: 'A URI that points to the source file. See `GWMediaPlayer.fromURIToAbsolute()` for how to convert to a URL'
+  MediaCodecs:
+    type: array
+    description: 'An array of codecs contained within the source file. Items should follow RFC6381'
+    items:
+    - type: string
 properties:
   version: { type: integer }
   songs:
@@ -123,6 +128,7 @@ properties:
           - required: [ type, url ]
             properties:
               type: { type: string, format: mimetype }
+              codecs: { "$ref": "#/$defs/MediaCodecs" }
               uri: { "$ref": "#/$defs/GWRadioURI" }
               previews:
                 description: >-
@@ -134,8 +140,9 @@ properties:
                     display_type:
                       description: 'Used to determine how the media should be displayed. See GWMediaPlayer.EDisplayType'
                       type: string
-                    uri: { "$ref": "#/$defs/GWRadioURI" }
                     type: { type: string, format: mimetype }
+                    codecs: { "$ref": "#/$defs/MediaCodecs" }
+                    uri: { "$ref": "#/$defs/GWRadioURI" }
                     size: { type: string }
 ```