Explicit reject for non video senders/receivers

Author: youennf

index.bs

@@ -408,6 +408,7 @@ The <dfn attribute for="RTCRtpScriptTransformer">writable</dfn> getter steps are
 
 The <dfn>generate key frame algorithm</dfn>, given |promise|, |encoder| and |rids|, 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 |rids| is defined, validate each of the RID values in |rids|.
     If any RID value is invalid, reject |promise| with {{NotAllowedError}} and abort these steps.
 1. Gather a list of video encoders, named |videoEncoders| from |encoder|.
@@ -420,6 +421,7 @@ The <dfn>generate key frame algorithm</dfn>, given |promise|, |encoder| and |rid
 
 The <dfn>send request key frame algorithm</dfn>, given |promise| and |depacketizer|, is defined by running these steps:
 1. If |depacketizer| is undefined, reject |promise| with {{InvalidStateError}}, abort these steps.
+1. If |depacketizer| is not processing video packets, reject |promise| with {{InvalidStateError}}, abort these steps.
 1. If sending a Full Intra Request (FIR) by |depacketizer|'s receiver is not deemed appropriate, [=resolve=] |promise| with undefined and abort these steps.
     Section 4.3.1 of [[RFC5104]] provides guidelines of how and when it is appropriate to sending a Full Intra Request.
 1. Generate a Full Intra Request (FIR) packet as defined in section 4.3.1 of [[RFC5104]] and send it through |depacketizer|'s receiver.