1.2.3 and 1.2.5: Add note from EN 301 549 describing audio descriptions

This is exactly how the notes appear in the V20 draft of the EN 301 549.

Author: maryjom

comments-by-guideline-and-success-criterion.md

@@ -69,6 +69,10 @@ The WCAG 2 definition of “[audio description](https://www.w3.org/TR/WCAG22/#df
 <div class="note wcag2ict">
 
 Secondary or alternate audio tracks are commonly used for this purpose.</div>
+<div class="note wcag2ict">
+	
+Audio descriptions (also called "video descriptions" and "described videos") add descriptive information of important visual information needed to understand the video content, including text displayed in the video. Where the main audio track of the video fully describes important visual information, audio descriptions would not be needed at all as the requirement would already be met. When audio descriptions are needed, one way to implement them is by providing a second audio track for the audio-video media.</div>
+	
 <div class="note wcag2ict software">
 
 See also the [Comments on Closed Functionality](#comments-on-closed-functionality).</div>
@@ -95,6 +99,9 @@ The WCAG 2 definition of “[audio description](https://www.w3.org/TR/WCAG22/#df
 <div class="note wcag2ict">
 
 Secondary or alternate audio tracks are commonly used for this purpose.</div>
+<div class="note wcag2ict">
+	
+Audio descriptions (also called "video descriptions" and "described videos") add descriptive information of important visual information needed to understand the video content, including text displayed in the video. Where the main audio track of the video fully describes important visual information, audio descriptions would not be needed at all as the requirement would already be met. When audio descriptions are needed, one way to implement them is by providing a second audio track for the audio-video media.</div>
 
 #### adaptable