Add support for Remote Playback API (and some cleanup) #134

pthatcherg · 2019-01-05T23:20:27Z

Add the protocol message for Remote Playback
Add the mapping from API to messages
Cleanup some terminology used by the Presentation API to make the two be in sync
Switch everything to using the "definition list" of bikeshed, which seems like a better fit

And also cleanup: - key/value lists to use better format - links to document sections better

takumif · 2019-01-09T19:40:31Z

index.bs

+controller may send a remote-playback-availability-request message with the
+following values:
+
+: urls


Please correct me if I'm wrong, but wouldn't we always be querying with a single URL (URL of the media element)?
https://w3c.github.io/remote-playback/#dom-remoteplayback-watchavailability

Media elements can have multiple resource URLs.

baylesj

Looks pretty good to me, I have some spec questions as well as minor grammar nits. Thanks for putting this together!

baylesj · 2019-02-26T19:08:15Z

index.bs

+  5 : bool ; selected
+}
+
+track-track-state = {


I'm sure some of this is my unfamilliarity with the spec best practices, but why wouldn't we just have mode as part of track-state above?

Are there instances where we would have track-state but not track-track state?

Do audio or video track-states also have modes? Always? Sometimes?

I think this should be text-track-state.

Indeed, it was a typo. I changed it to text-track-state.

baylesj · 2019-02-26T19:09:00Z

index.bs

+
+media-error = [
+  code: &(
+    user-aborted: 1


Would it be useful to have an error code for an internal crash, e.g. something not necessarily decode or network? Or does that scenario not happen?

OK, I added unknown-error for now

baylesj · 2019-02-26T19:13:12Z

index.bs

+}
+
+remote-playback-state = {
+  ? 1: (rate: bool, preload: bool, poster: bool, added-text-track: bool, added-cues: bool) ; supports


Should this also use the ampersand syntax below? I'm not familiar with this markup language.

Yes. I added it.

baylesj · 2019-02-26T19:15:19Z

index.bs

+}
+
+; type key 118
+remote-playback-termination-response = {


This type isn't used anywhere. Delete? I don't think we need a response?

We do, but I had a typo where I put in the wrong name for the message. I fixed it, so you should be able to see it now.

baylesj · 2019-02-26T19:33:02Z

index.bs

+availability request.
+
+To save power, the controller may disconnect the QUIC connection and
+later reconnect to send availablity requests and receive availability


Spelling mistake on this line

baylesj · 2019-02-26T21:29:06Z

index.bs

+    [HtmlMediaElement.played](https://html.spec.whatwg.org/multipage/media.html#dom-media-played).
+
+: seekable-time-ranges
+:: The time ranges for which media is seekable (ranges the controller or the


Super nit: can we rephrase without a parenthetical insert?

E.g.

:: The time ranges the controller or receiver may seek to

baylesj · 2019-02-26T21:31:40Z

index.bs

+    [HtmlMediaElement.videoHeight](https://html.spec.whatwg.org/multipage/media.html#dom-media-videoheight).
+
+: audio-tracks
+:: The audio tracks available, which can individually enabled or disabled.  See


Grammar nit: here and below, the syntax "The <foo> available" is usually phrased as "The available <foo>."

Consider:

:: The available audio tracks. Each track can be individually enabled or disabled.

baylesj · 2019-02-26T21:32:43Z

index.bs

+    [HtmlMediaElement.audioTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-audiotracks)
+
+: video-tracks
+:: The video tracks available, one of which can be selected.  See


Grammar nit: Is it exactly zero or one tracks that can be selected? Would be cleaner as:

:: The available video tracks. Only one track may be selected.

baylesj · 2019-02-26T21:33:26Z

index.bs

+    [HtmlMediaElement.videoTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-videotracks).
+    The controller can also add cues to and remove cues from text tracks.
+
+


Nit: extra newlines.

baylesj · 2019-02-26T21:41:12Z

index.bs

+remote-playback-modify-response and remote-playback-state-event messages to
+change the local media element based on changes to the remote playback state.
+
+<!-- TODO: Have a very descriptive, precise algorithm for what messages to send


Nit: can we track these TODOs: as issues in the GitHub repository? I think a separate patch converting the TODOs to issues would be handy.

Yes, we should have issues for them.

markafoltz

Overall looks great. I think there are some areas where the remote playback synchronization could be clarified, but most comments are minor editing suggestions. It might make sense to respond to the high level feedback and land as-is, then one of us can follow up with a copy editing cleanup PR.

markafoltz · 2019-03-26T20:36:35Z

index.bs

-presentation request URL.
+We borrow terminology from the [[PRESENTATION-API|Presentation API]]. We call
+the agent that is used to discover and initiate presentation of Web content on
+another device the [=controller=] (or [=controlling user agent=] when it is a


The controller is the application that is requesting presentation, not the agent. If you want to redefine it here, then please be specific that this is a different definition than the API's. But we'd then want to go back and change the API to prevent rampant confusion.

From a protocol perspective, it's the browser that's the controller, even if it's doing things on behalf of a "browsing context" that's the controller behind the curtains. I can try and make this clear in this text.

markafoltz · 2019-03-26T20:45:17Z

index.bs

+the agent that is used to discover and initiate presentation of Web content on
+another device the [=controller=] (or [=controlling user agent=] when it is a
+browser).  We call the agent on the device rendering the Web content the
+[=receiver=] or [=presentation display=] (or [=receiving user agent=] when it is


Let's just use receiver for the agent that answers requests and renders presentations.

What is the distinction between "receiver" and "receiving user agent"? Shouldn't every agent be a user agent?

A receiver could potentially launch a non-user agent. Maybe it has specific native code to use for certain URLs that aren't user agents.

If you want to change the term Remote Playback "receiver" into something other "receiver", could we debate what that term should be and change it in a follow-up PR? It might take a while to pick a different noun.

I'll make a github issue to remember to discuss this (and also the word "controller")

markafoltz · 2019-03-26T20:50:22Z

index.bs

-[[PRESENTATION-API|Presentation API]].  A subsequent section will
-define how APIs in [[PRESENTATION-API|Presentation API]] map to the
+terminating, and controlling presentations as defined by
+[[PRESENTATION-API|Presentation API]]. [[#presentation-api]]


Do you need anchor text for #presentation-api to render something useful?

There are a bunch of places where this style is used in this doc, so I think it works.

markafoltz · 2019-03-26T20:50:41Z

index.bs

-    receiving updates about the URLs, should the availability change.
+: watch-duration
+:: The period of time that the controller is interested in receiving updates
+    about the URLs, should the availability change.


s/the/their/

markafoltz · 2019-03-26T20:51:48Z

index.bs

-   watch-id: An identifier the receiver may use when sending updates about URL
-    availability so that controller knows which URLs the receiver is referring
+: watch-id
+:: An identifier the receiver may use when sending updates about URL


Is this message meaningful to the controller without a watch-id? If not, make this a "should" or "must".

Made it "must".

markafoltz · 2019-03-27T00:39:29Z

index.bs

+    message, it is assumed there is no such major error.
+
+: epoch
+:: The "zero time" of the media timeline.  See


markafoltz · 2019-03-27T00:40:50Z

index.bs

+:: The "zero time" of the media timeline.  See
+    [HtmlMediaElement's timeline offset](https://html.spec.whatwg.org/multipage/media.html#timeline-offset) and 
+    [HtmlMediaElement.getStartDate()](https://html.spec.whatwg.org/multipage/media.html#dom-media-getstartdate).
+    If not present in the intial state in the remote-playback-start-response


Do we need to accommodate clock skew between the sender and receiver? Otherwise it seems like the timelines are going to be out of sync w.r.t. actual, wall clock time.

Wall clock times will always be out of sync between sender and receiver (there is no solution to clock sync). I think the controller will have to deal with that however it sees fit.

markafoltz · 2019-03-27T00:41:13Z

index.bs

+    message, it is assumed to be unknown.
+
+: duration
+:: The duration of the media timeline.  See


markafoltz · 2019-03-27T00:41:37Z

index.bs

+:: The duration of the media timeline.  See
+    [HtmlMediaElement.duration](https://html.spec.whatwg.org/multipage/media.html#dom-media-duration).
+    If not present in the intial state in the remote-playback-start-response
+    message, it is assumed to be unknown.  For unbounded streams, it may be "forever".


Is "forever" a special numeric value (NaN)?

No, it's more like a CDDL type union.

markafoltz · 2019-03-27T00:43:34Z

index.bs

+
+: text-tracks
+:: The text tracks available, which can be individually shown, hidden, or disabled.  See
+    [HtmlMediaElement.videoTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-videotracks).


s/videoTracks/textTracks/?

pthatcherg added 3 commits January 4, 2019 14:55

Add remote playback API section

54a69a5

And also cleanup: - key/value lists to use better format - links to document sections better

Add all of the Remote Playback messages

85bd1c9

Merge with gh-pages

e12f905

takumif reviewed Jan 9, 2019

View reviewed changes

baylesj reviewed Feb 26, 2019

View reviewed changes

btolsch mentioned this pull request Mar 20, 2019

Add capabilities #140

Merged

markafoltz approved these changes Mar 27, 2019

View reviewed changes

pthatcherg added 2 commits April 1, 2019 10:56

Respond to PR review.

d71ffaa

Merge with master

517783b

pthatcherg merged commit 3352f78 into gh-pages Apr 1, 2019

markafoltz mentioned this pull request Apr 4, 2019

[Control Protocol] Remote Playback API control protocol #12

Closed

markafoltz deleted the remote-playback branch May 8, 2019 22:49

		[HtmlMediaElement.videoTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-videotracks).
		The controller can also add cues to and remove cues from text tracks.

Add support for Remote Playback API (and some cleanup) #134

Add support for Remote Playback API (and some cleanup) #134

Conversation

pthatcherg commented Jan 5, 2019

Choose a reason for hiding this comment

Choose a reason for hiding this comment

baylesj left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

baylesj Feb 26, 2019 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

markafoltz left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

baylesj Feb 26, 2019 •

edited

Loading