Accessibility/IA2 1.3: Difference between revisions

Accessibility/IA2 1.3 (view source)

Revision as of 14:09, 8 June 2011

618 bytes added , 8 June 2011

→‎Text cues

Surkov.alexander

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 ===Text cues===
 Propose: provide a way to handle text descriptions and other text cues.
-) when the browser has a new cue available for a text track, then the browser fires a "MEDIA_TEXT_CUE_CHANGE" event at AT
-) AT picks up the cue, which causes the browser to set a "pauseOnExit" flag to true on this cue; from here on, the AT and the video play asynchronously
-.a) AT reads out cue and calls "GET_NEXT_CUE" when it is finished, which causes the browser to set the "pauseOnExit" flag to false and unpauses the video if it is paused
-.b) in parallel the browser plays video until the end of the cue; if the "pauseOnExit" flag is true when it reaches the end time of the cue, the video pauses, otherwise it continues playing
-repeat from 1)
-It should be enough:
 <pre>
@@ Line 303: / Line 291: @@
    /**
-    * Makes video paused when current cue end time is reached.
+    * Switch the state that makes video paused when current cue end time is reached.
     */
    HRESULT pauseOnExit(
@@ Line 310: / Line 298: @@
 </pre>
-[Silvia interface]
+Silvia algorithm:
+) When the browser has a new cue available for a text track, then the browser fires a "MEDIA_TEXT_CUE_CHANGE" event at AT
+) AT picks up the cue, which causes the browser to set a "pauseOnExit" flag to true on this cue; from here on, the AT and the video play asynchronously
+.1) AT reads out cue and calls "cueText" property when it is finished, which causes the browser to set the "pauseOnExit" flag to false and unpauses the video if it is paused
+.2) in parallel the browser plays video until the end of the cue; if the "pauseOnExit" flag is true when it reaches the end time of the cue, the video pauses, otherwise it continues playing
+repeat from 1)
+Compare to original algorithm:
+) When the browser has a new cue available for a text track, then the browser fires a "MEDIA_TEXT_CUE_CHANGE" event at AT
+) AT handles event and picks up the cue and starts reading of it
+) Do 1) and if AT doesn't picks up the cue when it handles event then stop the video until AT pick up the cue.
+The disadvantage of this: since video and browser works async then this algorithm may results in that video plays while AT still reads the previous cue. I don't know if it's problem in practice, since we shouldn't get big delays because of async communications.
+[Track Cue interface]
 <pre>
 interface IAccessibleTextTrackCue : public IUnknown