Merge pull request #277 from jan-ivar/clarifygenkeyframe

Clarify that generateKeyFrame() rejects immediately for audio receivers

Author: guidou

index.bs

@@ -998,7 +998,7 @@ or Full Intra Refresh (FIR), queue a task to perform the following steps:
 
 The <dfn abstract-op>generate key frame algorithm</dfn>, given |promise|, |encoder| and |rid|, is defined by running these steps:
 1. If |encoder| is undefined, reject |promise| with {{InvalidStateError}}, abort these steps.
-1. If |encoder| is not processing video frames, reject |promise| with {{InvalidStateError}}, abort these steps.
+1. If |encoder| does not belong to a video {{RTCRtpReceiver}}, reject |promise| with {{InvalidStateError}}, abort these steps.
 1. If |rid| is defined, but does not conform to the grammar requirements specified
     in Section 10 of [[!RFC8851]], then reject |promise| with {{TypeError}} and abort
     these steps.