Bug 94786 – MediaController play() doesn't work

• Status: RESOLVED
• Resolution: WONTFIX
• Component: Media

[Changbin Shao]

reproduce step:
1. open attached file in safari/chrome
2. check if video is able to display.

result:
video is not able to play.

[Changbin Shao]

Created attachment 160105 [details]
test file

test.html

[Jer Noble]

Unfortunately, this code is working exactly as expected.  The spec says:

"A MediaController is a blocked media controller ... if all of its slaved media elements have their paused attribute set to true."

Since the test case has a MediaController with a single slaved media element, and that media element is paused, the MediaController is a blocked media controller, and play() will not cause playback to start until the slaved media element is unpaused.

[Changbin Shao]

Thanks, it make sense for me now. While I still have questions here.
For instance, there are two video tags, with id vid1 & vid2.
     
var con = new MediaController();
vid1.controller = con;
vid2.controller = con;
con.play();//won't work since MediaController is blocked.
vid1.play();//won't work since MediaController is blocked(because MediaElement 2 is still paused) 
vid2.play(); //works, since MediaController is not blocked now.
con.pause();//MediaController is paused. How about its slaved elements, should be paused or not? 
con.play();//what the result should be? As the spec says: "A MediaController is a blocked media controller if the MediaController is a paused media controller...",so no video should play?

[Jer Noble]

(In reply to comment #3)
> Thanks, it make sense for me now. While I still have questions here.
> For instance, there are two video tags, with id vid1 & vid2.
> 
> var con = new MediaController();
> vid1.controller = con;
> vid2.controller = con;
> con.play();//won't work since MediaController is blocked.
> vid1.play();//won't work since MediaController is blocked(because MediaElement 2 is still paused) 

Not quite.  The MediaController is only blocked if *all* of its slaved media elements are paused.  So at this point, the MediaController goes from a blocked media controller to a playing one.  Vid1 will begin playing.

> vid2.play(); //works, since MediaController is not blocked now.
> con.pause();//MediaController is paused. How about its slaved elements, should be paused or not? 

They are blocked on their MediaController.  They are still "playing" technically, but their timelines are stopped.

> con.play();//what the result should be? As the spec says: "A MediaController is a blocked media controller if the MediaController is a paused media controller...",so no video should play?

Once the MediaController goes from a paused media controller to a playing media controller, the slaved media elements should begin playing.  (Assuming the MediaController does not become blocked for some other reason, like one of the slaved media elements stalling, etc.)

[Changbin Shao]

Thanks a lot for your explanation! 

(In reply to comment #4)
> (In reply to comment #3)
> > Thanks, it make sense for me now. While I still have questions here.
> > For instance, there are two video tags, with id vid1 & vid2.
> > 
> > var con = new MediaController();
> > vid1.controller = con;
> > vid2.controller = con;
> > con.play();//won't work since MediaController is blocked.
> > vid1.play();//won't work since MediaController is blocked(because MediaElement 2 is still paused) 
> 
> Not quite.  The MediaController is only blocked if *all* of its slaved media elements are paused.  So at this point, the MediaController goes from a blocked media controller to a playing one.  Vid1 will begin playing.

Just for your information. Spec says: "A MediaController is a blocked media controller...if any of its slaved media elements whose autoplaying flag is true still have their paused attribute set to true" && "All media elements have an autoplaying flag, which must begin in the true state", so I think vid2 still blocks mediaController, thus vid1 is still not able to play. Checked my idea on Chrome. 
 
> > vid2.play(); //works, since MediaController is not blocked now.
> > con.pause();//MediaController is paused. How about its slaved elements, should be paused or not? 
> 
> They are blocked on their MediaController.  They are still "playing" technically, but their timelines are stopped.
> 
> > con.play();//what the result should be? As the spec says: "A MediaController is a blocked media controller if the MediaController is a paused media controller...",so no video should play?
> 
> Once the MediaController goes from a paused media controller to a playing media controller, the slaved media elements should begin playing.  (Assuming the MediaController does not become blocked for some other reason, like one of the slaved media elements stalling, etc.)