RTCRtpSender send should return a promise #469

murillo128 opened this Issue Apr 15, 2016 · 5 comments


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Not sure if it is duplicated, but just in cae.

Currently, RTCRtpSender.send() returns void and error is launched if

This event must be fired if an issue is found with the RTCRtpParameters object passed to send(), that is not immediately detected.

According to the promise best practices (https://www.w3.org/2001/tag/doc/promises-guide), about when to use promises this should be changed to a promise instead of an error handler

Because promises can be subscribed to even after they’ve already been fulfilled or rejected, they can be very useful for a certain class of "event." When something only happens once, and authors often want to observe the status of it after it’s .already occurred, providing a promise that becomes fulfilled when that eventuality comes to pass gives a very convenient API.

The prototypical example of such an "event" is a loaded indicator: a resource such as an image, font, or even document, could provide a loaded property that is a promise that becomes fulfilled only when the resource has fully loaded (or becomes rejected if there’s an error loading the resource). Then, authors can always queue up actions to be executed once the resource is ready by doing resource.loaded.then(onLoaded, onFailure). This will work even if the resource was loaded already, queueing a microtask to execute onLoaded. This is in contrast to an event model, where if the author is not subscribed at the time the event fires, that information is lost.


$related #399


Could we return the browser filled RTCRtpParameters on success?? ;)

Promise<RTCRtpParameters> send(RTCRtpParameters)
robin-raymond commented Apr 15, 2016 edited

@murillo128 ;) not in this bug -- but nice try! I know that was a semi-serious-joking but let's keep the issues separate.

FYI - I am personally in favour of it, but I would prefer a RTCRtpSender.getParameters() because I'm also in favour of returning the filled parameters for a receiver with a RTCRtpReceiver.getParameters(); the receiver can't be done as a promise since it's filled in an "ongoing" basis so I'd like them somewhat consistent for the future if we did that later. Alas, I've not been able to convince others in the CG that is has enough value to merit is mandatory inclusion in the API and I've made the same arguments as you and @ibc (I believe).

UPDATE: To be clear, a method like RTCRtpSender.getParameters() would require a promise result from send() to know when the developer can fetch the parameters and expect to get the resulting values.

ibc commented Apr 16, 2016

Could we return the browser filled RTCRtpParameters on success?? ;)

I don't want to restart the trending topic :) but getting the full parameters once send() is called is of little use. That's why I suggested:


var fullParams = rtpSender.getParameters();

// Signal them if needed


Don't reply please! :)

@aboba aboba added PR exists and removed to-do-next-draft labels Apr 25, 2016
@aboba aboba added a commit that referenced this issue Apr 25, 2016
@aboba aboba Promise for send(), receive() and setTransport()
Addresses the following Issues: 
@aboba aboba added a commit that referenced this issue Apr 26, 2016
@aboba aboba Examples: async usage of send(), receive() and setTransport()
Fix for Issues: 

More work to do (please do not merge yet).

Looks better.

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