From 462a71755ca5d6c69bfc97bf644e5e1430b3424d Mon Sep 17 00:00:00 2001
From: cnderrauber <zengjie9004@gmail.com>
Date: Tue, 12 Dec 2023 13:34:11 +0800
Subject: [PATCH] Answer to paused simucalst stream correctly

Answer to paused simucalst stream correctly
---
 constants.go |  2 ++
 sdp.go       | 38 ++++++++++++++++++++++++++++++++------
 sdp_test.go  | 27 ++++++++++++++++-----------
 3 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/constants.go b/constants.go
index 94ba78494a6..79c2fa38074 100644
--- a/constants.go
+++ b/constants.go
@@ -27,6 +27,8 @@ const (
 
 	sdpAttributeRid = "rid"
 
+	sdpAttributeSimulcast = "simulcast"
+
 	rtpOutboundMTU = 1200
 
 	rtpPayloadTypeBitmask = 0x7F
diff --git a/sdp.go b/sdp.go
index 44c42ae40a3..1a9b29566cd 100644
--- a/sdp.go
+++ b/sdp.go
@@ -232,12 +232,30 @@ func trackDetailsToRTPReceiveParameters(t *trackDetails) RTPReceiveParameters {
 	return RTPReceiveParameters{Encodings: encodings}
 }
 
-func getRids(media *sdp.MediaDescription) map[string]string {
-	rids := map[string]string{}
+func getRids(media *sdp.MediaDescription) map[string]*simulcastRid {
+	rids := map[string]*simulcastRid{}
+	var simulcastAttr string
 	for _, attr := range media.Attributes {
 		if attr.Key == sdpAttributeRid {
 			split := strings.Split(attr.Value, " ")
-			rids[split[0]] = attr.Value
+			rids[split[0]] = &simulcastRid{attrValue: attr.Value}
+		} else if attr.Key == sdpAttributeSimulcast {
+			simulcastAttr = attr.Value
+		}
+	}
+	// process paused stream like "a=simulcast:send 1;~2;~3"
+	if simulcastAttr != "" {
+		if space := strings.Index(simulcastAttr, " "); space > 0 {
+			simulcastAttr = simulcastAttr[space+1:]
+		}
+		ridStates := strings.Split(simulcastAttr, ";")
+		for _, ridState := range ridStates {
+			if ridState[:1] == "~" {
+				rid := ridState[1:]
+				if r, ok := rids[rid]; ok {
+					r.paused = true
+				}
+			}
 		}
 	}
 	return rids
@@ -379,7 +397,7 @@ func addSenderSDP(
 				sendRids = append(sendRids, encoding.RID)
 			}
 			// Simulcast
-			media.WithValueAttribute("simulcast", "send "+strings.Join(sendRids, ";"))
+			media.WithValueAttribute(sdpAttributeSimulcast, "send "+strings.Join(sendRids, ";"))
 		}
 
 		if !isPlanB {
@@ -475,10 +493,13 @@ func addTransceiverSDP(
 
 		for rid := range mediaSection.ridMap {
 			media.WithValueAttribute(sdpAttributeRid, rid+" recv")
+			if mediaSection.ridMap[rid].paused {
+				rid = "~" + rid
+			}
 			recvRids = append(recvRids, rid)
 		}
 		// Simulcast
-		media.WithValueAttribute("simulcast", "recv "+strings.Join(recvRids, ";"))
+		media.WithValueAttribute(sdpAttributeSimulcast, "recv "+strings.Join(recvRids, ";"))
 	}
 
 	addSenderSDP(mediaSection, isPlanB, media)
@@ -500,11 +521,16 @@ func addTransceiverSDP(
 	return true, nil
 }
 
+type simulcastRid struct {
+	attrValue string
+	paused    bool
+}
+
 type mediaSection struct {
 	id           string
 	transceivers []*RTPTransceiver
 	data         bool
-	ridMap       map[string]string
+	ridMap       map[string]*simulcastRid
 }
 
 func bundleMatchFromRemote(matchBundleGroup *string) func(mid string) bool {
diff --git a/sdp_test.go b/sdp_test.go
index a0d99b140f7..4696ce87279 100644
--- a/sdp_test.go
+++ b/sdp_test.go
@@ -381,8 +381,14 @@ func TestPopulateSDP(t *testing.T) {
 
 		tr := &RTPTransceiver{kind: RTPCodecTypeVideo, api: api, codecs: me.videoCodecs}
 		tr.setDirection(RTPTransceiverDirectionRecvonly)
-		ridMap := map[string]string{
-			"ridkey": "some",
+		ridMap := map[string]*simulcastRid{
+			"ridkey": {
+				attrValue: "some",
+			},
+			"ridPaused": {
+				attrValue: "some2",
+				paused:    true,
+			},
 		}
 		mediaSections := []mediaSection{{id: "video", transceivers: []*RTPTransceiver{tr}, ridMap: ridMap}}
 
@@ -392,21 +398,20 @@ func TestPopulateSDP(t *testing.T) {
 		assert.Nil(t, err)
 
 		// Test contains rid map keys
-		var found bool
+		var ridFound int
 		for _, desc := range offerSdp.MediaDescriptions {
 			if desc.MediaName.Media != "video" {
 				continue
 			}
-			for _, a := range desc.Attributes {
-				if a.Key == sdpAttributeRid {
-					if strings.Contains(a.Value, "ridkey") {
-						found = true
-						break
-					}
-				}
+			ridInSDP := getRids(desc)
+			if ridKey, ok := ridInSDP["ridkey"]; ok && !ridKey.paused {
+				ridFound++
+			}
+			if ridPaused, ok := ridInSDP["ridPaused"]; ok && ridPaused.paused {
+				ridFound++
 			}
 		}
-		assert.Equal(t, true, found, "Rid key should be present")
+		assert.Equal(t, 2, ridFound, "All rid keys should be present")
 	})
 	t.Run("SetCodecPreferences", func(t *testing.T) {
 		se := SettingEngine{}