Remove source/sink mixins, define keyframe event algo

Author: alvestrand

index.bs

@@ -591,24 +591,24 @@ partial interface DedicatedWorkerGlobalScope {
 };
 
 interface mixin RTCRtpScriptSource {
-    readonly attribute ReadableStream readable;
-    Promise<unsigned long long> generateKeyFrame(optional DOMString rid);
-    Promise<undefined> sendKeyFrameRequest();
 };
 
 interface mixin RTCRtpScriptSink {
-    readonly attribute WritableStream writable;
-    attribute EventHandler onkeyframerequest;
 };
 
 [Exposed=DedicatedWorker]
 interface RTCRtpScriptTransformer {
+    // Attributes and methods related to the transformer source
+    readonly attribute ReadableStream readable;
+    Promise<unsigned long long> generateKeyFrame(optional DOMString rid);
+    Promise<undefined> sendKeyFrameRequest();
+    // Attributes and methods related to the transformer sink
+    readonly attribute WritableStream writable;
+    attribute EventHandler onkeyframerequest;
+    // Attributes for configuring the Javascript code
     readonly attribute any options;
 };
 
-RTCRtpScriptTransformer includes RTCRtpScriptSource;
-RTCRtpScriptTransformer includes RTCRtpScriptSink;
-
 [Exposed=Window]
 interface RTCRtpScriptTransform {
     constructor(Worker worker, optional any options, optional sequence<object> transfer);
@@ -652,12 +652,12 @@ Each RTCRtpScriptTransform has the following set of [$association steps$], given
     1. Set |transformer|.`[[encoder]]` to |encoder|.
     1. Set |transformer|.`[[depacketizer]]` to |depacketizer|.
 
-The <dfn method for="RTCRtpScriptSource">generateKeyFrame(|rid|)</dfn> method steps are:
+The <dfn method for="RTCRtpScriptTransform">generateKeyFrame(|rid|)</dfn> method steps are:
 1. Let |promise| be a new promise.
 1. Run the [$generate key frame algorithm$] with |promise|, |this|.`[[encoder]]` and |rid|.
 1. Return |promise|.
 
-The <dfn method for="RTCRtpScriptSource">sendKeyFrameRequest()</dfn> method steps are:
+The <dfn method for="RTCRtpScriptTransform">sendKeyFrameRequest()</dfn> method steps are:
 1. Let |promise| be a new promise.
 1. Run the [$send request key frame algorithm$] with |promise| and |this|.`[[depacketizer]]`.
 1. Return |promise|.
@@ -671,21 +671,34 @@ This allows algorithms to go from an {{RTCRtpScriptTransformer}} object to its {
 The <dfn attribute for="RTCRtpScriptTransformer">options</dfn> getter steps are:
 1. Return [=this=].`[[options]]`.
 
-The <dfn attribute for="RTCRtpScriptSource">readable</dfn> getter steps are:
+The <dfn attribute for="RTCRtpScriptTransform">readable</dfn> getter steps are:
 1. Return [=this=].`[[readable]]`.
 
-The <dfn attribute for="RTCRtpScriptSink">writable</dfn> getter steps are:
+The <dfn attribute for="RTCRtpScriptTransform">writable</dfn> getter steps are:
 1. Return [=this=].`[[writable]]`.
 
-The <dfn attribute for="RTCRtpScriptSink">onbandwidthestimate</dfn> EventHandler has type bandwidthestimate.
+The <dfn attribute for="RTCRtpScriptTransform">onbandwidthestimate</dfn> EventHandler has type bandwidthestimate.
 
-The <dfn attribute for="RTCRtpScriptSink">onkeyframerequest</dfn> EventHandler has type keyframerequest.
+The <dfn attribute for="RTCRtpScriptTransform">onkeyframerequest</dfn> EventHandler has type keyframerequest.
 
 ## Events ## {#RTCRtpScriptTransformer-events}
 
 The following events fire on an {{RTCRtpScriptTransformer}}:
 
-* keyframerequest of type {{KeyFrameRequestEvent}} - fired when the sink determines that a key frame has been requested. In the context of {{RTCRtpScriptTransform}}, if the event is not cancelled, the information will be passed to the source as if the generateKeyFrame() function had been called. <!-- NOTE IN DRAFT: generateKeyFrame() and requestKeyFrame() should merge -->
+* keyframerequest of type {{KeyFrameRequestEvent}} - fired when the sink determines that a key frame has been requested.
+
+The steps that generate an event of type {{KeyFrameRequestEvent}} are as follows:
+
+Given a {{RTCRtpScriptTransformer}} `transform`:
+
+When `transform`'s `[[encoder]]` receives a keyframe request, for instance from an incoming RTCP Picture Loss Indication (PLI)
+or Full Intra Refresh (FIR), queue
+a task to perform the following steps:
+
+1. Set `rid` to the RID of the appropriate layer, or undefined if the request is not for a specific layer.
+1. Fire a cancelable event of type {{KeyFrameRequestEvent}} on `transform`, with {{KeyFrameRequestEvent/rid}} set to `rid`.
+1. If the event is cancelled, abort these steps.
+1. Run the [$generate key frame algorithm$] with a new promise, `transform`.`[[encoder]]` and `rid`.
 
 ## KeyFrame Algorithms ## {#KeyFrame-algorithms}