webrtc: support reading and publishing multichannel Opus (#3371)

go.mod

@@ -20,7 +20,7 @@ require (
 	github.com/gorilla/websocket v1.5.1
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
 	github.com/matthewhartstonge/argon2 v1.0.0
-	github.com/pion/ice/v2 v2.3.11
+	github.com/pion/ice/v2 v2.3.24
 	github.com/pion/interceptor v0.1.29
 	github.com/pion/logging v0.2.2
 	github.com/pion/rtcp v1.2.14
@@ -58,12 +58,12 @@ require (
 	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
 	github.com/pion/datachannel v1.5.5 // indirect
 	github.com/pion/dtls/v2 v2.2.7 // indirect
-	github.com/pion/mdns v0.0.9 // indirect
+	github.com/pion/mdns v0.0.12 // indirect
 	github.com/pion/randutil v0.1.0 // indirect
-	github.com/pion/sctp v1.8.8 // indirect
+	github.com/pion/sctp v1.8.16 // indirect
 	github.com/pion/srtp/v2 v2.0.18 // indirect
 	github.com/pion/stun v0.6.1 // indirect
-	github.com/pion/transport/v2 v2.2.3 // indirect
+	github.com/pion/transport/v2 v2.2.4 // indirect
 	github.com/pion/turn/v2 v2.1.3 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
@@ -81,4 +81,4 @@ replace code.cloudfoundry.org/bytefmt => github.com/cloudfoundry/bytefmt v0.0.0-
 
 replace github.com/pion/ice/v2 => github.com/aler9/ice/v2 v2.0.0-20231112223552-32d34dfcf3a1
 
-replace github.com/pion/webrtc/v3 => github.com/aler9/webrtc/v3 v3.0.0-20231112223655-e402ed2689c6
+replace github.com/pion/webrtc/v3 => github.com/aler9/webrtc/v3 v3.0.0-20240519175023-87091c864d51

go.sum

@@ -12,8 +12,8 @@ github.com/alecthomas/repr v0.4.0 h1:GhI2A8MACjfegCPVq9f1FLvIBS+DrQ2KQBFZP1iFzXc
 github.com/alecthomas/repr v0.4.0/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
 github.com/aler9/ice/v2 v2.0.0-20231112223552-32d34dfcf3a1 h1:fD6eZt+3/t8bzFn6ZZA2eP63xBP06v3EPfPJu8DO8ys=
 github.com/aler9/ice/v2 v2.0.0-20231112223552-32d34dfcf3a1/go.mod h1:lT3kv5uUIlHfXHU/ZRD7uKD/ufM202+eTa3C/umgGf4=
-github.com/aler9/webrtc/v3 v3.0.0-20231112223655-e402ed2689c6 h1:wMd3D1mLghoYYh31STig8Kwm2qi8QyQKUy09qUUZrVw=
-github.com/aler9/webrtc/v3 v3.0.0-20231112223655-e402ed2689c6/go.mod h1:1CaT2fcZzZ6VZA+O1i9yK2DU4EOcXVvSbWG9pr5jefs=
+github.com/aler9/webrtc/v3 v3.0.0-20240519175023-87091c864d51 h1:TNY2uVEkXsdZBc0CR0OgyDEow6Wep7uj8XuYUh4CCRY=
+github.com/aler9/webrtc/v3 v3.0.0-20240519175023-87091c864d51/go.mod h1:M1RAe3TNTD1tzyvqHrbVODfwdPGSXOUo/OgpoGGJqFY=
 github.com/asticode/go-astikit v0.30.0 h1:DkBkRQRIxYcknlaU7W7ksNfn4gMFsB0tqMJflxkRsZA=
 github.com/asticode/go-astikit v0.30.0/go.mod h1:h4ly7idim1tNhaVkdVBeXQZEE3L0xblP7fCWbgwipF0=
 github.com/asticode/go-astits v1.13.0 h1:XOgkaadfZODnyZRR5Y0/DWkA9vrkLLPLeeOvDwfKZ1c=
@@ -137,28 +137,24 @@ github.com/pion/datachannel v1.5.5 h1:10ef4kwdjije+M9d7Xm9im2Y3O6A6ccQb0zcqZcJew
 github.com/pion/datachannel v1.5.5/go.mod h1:iMz+lECmfdCMqFRhXhcA/219B0SQlbpoR2V118yimL0=
 github.com/pion/dtls/v2 v2.2.7 h1:cSUBsETxepsCSFSxC3mc/aDo14qQLMSL+O6IjG28yV8=
 github.com/pion/dtls/v2 v2.2.7/go.mod h1:8WiMkebSHFD0T+dIU+UeBaoV7kDhOW5oDCzZ7WZ/F9s=
-github.com/pion/interceptor v0.1.25/go.mod h1:wkbPYAak5zKsfpVDYMtEfWEy8D4zL+rpxCxPImLOg3Y=
 github.com/pion/interceptor v0.1.29 h1:39fsnlP1U8gw2JzOFWdfCU82vHvhW9o0rZnZF56wF+M=
 github.com/pion/interceptor v0.1.29/go.mod h1:ri+LGNjRUc5xUNtDEPzfdkmSqISixVTBF/z/Zms/6T4=
 github.com/pion/logging v0.2.2 h1:M9+AIj/+pxNsDfAT64+MAVgJO0rsyLnoJKCqf//DoeY=
 github.com/pion/logging v0.2.2/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
 github.com/pion/mdns v0.0.7/go.mod h1:4iP2UbeFhLI/vWju/bw6ZfwjJzk0z8DNValjGxR/dD8=
-github.com/pion/mdns v0.0.9 h1:7Ue5KZsqq8EuqStnpPWV33vYYEH0+skdDN5L7EiEsI4=
-github.com/pion/mdns v0.0.9/go.mod h1:2JA5exfxwzXiCihmxpTKgFUpiQws2MnipoPK09vecIc=
+github.com/pion/mdns v0.0.12 h1:CiMYlY+O0azojWDmxdNr7ADGrnZ+V6Ilfner+6mSVK8=
+github.com/pion/mdns v0.0.12/go.mod h1:VExJjv8to/6Wqm1FXK+Ii/Z9tsVk/F5sD/N70cnYFbk=
 github.com/pion/randutil v0.1.0 h1:CFG1UdESneORglEsnimhUjf33Rwjubwj6xfiOXBa3mA=
 github.com/pion/randutil v0.1.0/go.mod h1:XcJrSMMbbMRhASFVOlj/5hQial/Y8oH/HVo7TBZq+j8=
-github.com/pion/rtcp v1.2.10/go.mod h1:ztfEwXZNLGyF1oQDttz/ZKIBaeeg/oWbRYqzBM9TL1I=
 github.com/pion/rtcp v1.2.12/go.mod h1:sn6qjxvnwyAkkPzPULIbVqSKI5Dv54Rv7VG0kNxh9L4=
 github.com/pion/rtcp v1.2.14 h1:KCkGV3vJ+4DAJmvP0vaQShsb0xkRfWkO540Gy102KyE=
 github.com/pion/rtcp v1.2.14/go.mod h1:sn6qjxvnwyAkkPzPULIbVqSKI5Dv54Rv7VG0kNxh9L4=
-github.com/pion/rtp v1.8.2/go.mod h1:pBGHaFt/yW7bf1jjWAoUjpSNoDnw98KTMg+jWWvziqU=
 github.com/pion/rtp v1.8.3/go.mod h1:pBGHaFt/yW7bf1jjWAoUjpSNoDnw98KTMg+jWWvziqU=
 github.com/pion/rtp v1.8.7-0.20240429002300-bc5124c9d0d0 h1:yPAphilskTN7U3URvBVxlVr0PzheMeWqo7PaOqh//Hg=
 github.com/pion/rtp v1.8.7-0.20240429002300-bc5124c9d0d0/go.mod h1:pBGHaFt/yW7bf1jjWAoUjpSNoDnw98KTMg+jWWvziqU=
 github.com/pion/sctp v1.8.5/go.mod h1:SUFFfDpViyKejTAdwD1d/HQsCu+V/40cCs2nZIvC3s0=
-github.com/pion/sctp v1.8.8 h1:5EdnnKI4gpyR1a1TwbiS/wxEgcUWBHsc7ILAjARJB+U=
-github.com/pion/sctp v1.8.8/go.mod h1:igF9nZBrjh5AtmKc7U30jXltsFHicFCXSmWA2GWRaWs=
-github.com/pion/sdp/v3 v3.0.6/go.mod h1:iiFWFpQO8Fy3S5ldclBkpXqmWy02ns78NOKoLLL0YQw=
+github.com/pion/sctp v1.8.16 h1:PKrMs+o9EMLRvFfXq59WFsC+V8mN1wnKzqrv+3D/gYY=
+github.com/pion/sctp v1.8.16/go.mod h1:P6PbDVA++OJMrVNg2AL3XtYHV4uD6dvfyOovCgMs0PE=
 github.com/pion/sdp/v3 v3.0.9 h1:pX++dCHoHUwq43kuwf3PyJfHlwIj4hXA7Vrifiq0IJY=
 github.com/pion/sdp/v3 v3.0.9/go.mod h1:B5xmvENq5IXJimIO4zfp6LAe1fD9N+kFv+V/1lOdz8M=
 github.com/pion/srtp/v2 v2.0.18 h1:vKpAXfawO9RtTRKZJbG4y0v1b11NZxQnxRl85kGuUlo=
@@ -169,9 +165,9 @@ github.com/pion/transport v0.14.1 h1:XSM6olwW+o8J4SCmOBb/BpwZypkHeyM0PGFCxNQBr40
 github.com/pion/transport v0.14.1/go.mod h1:4tGmbk00NeYA3rUa9+n+dzCCoKkcy3YlYb99Jn2fNnI=
 github.com/pion/transport/v2 v2.0.0/go.mod h1:HS2MEBJTwD+1ZI2eSXSvHJx/HnzQqRy2/LXxt6eVMHc=
 github.com/pion/transport/v2 v2.2.1/go.mod h1:cXXWavvCnFF6McHTft3DWS9iic2Mftcz1Aq29pGcU5g=
-github.com/pion/transport/v2 v2.2.3 h1:XcOE3/x41HOSKbl1BfyY1TF1dERx7lVvlMCbXU7kfvA=
 github.com/pion/transport/v2 v2.2.3/go.mod h1:q2U/tf9FEfnSBGSW6w5Qp5PFWRLRj3NjLhCCgpRK4p0=
-github.com/pion/transport/v3 v3.0.1/go.mod h1:UY7kiITrlMv7/IKgd5eTUcaahZx5oUN3l9SzK5f5xE0=
+github.com/pion/transport/v2 v2.2.4 h1:41JJK6DZQYSeVLxILA2+F4ZkKb4Xd/tFJZRFZQ9QAlo=
+github.com/pion/transport/v2 v2.2.4/go.mod h1:q2U/tf9FEfnSBGSW6w5Qp5PFWRLRj3NjLhCCgpRK4p0=
 github.com/pion/transport/v3 v3.0.2 h1:r+40RJR25S9w3jbA6/5uEPTzcdn7ncyU44RWCbHkLg4=
 github.com/pion/transport/v3 v3.0.2/go.mod h1:nIToODoOlb5If2jF9y2Igfx3PFYWfuXi37m0IlWa/D0=
 github.com/pion/turn/v2 v2.1.2/go.mod h1:1kjnPkBcex3dhCU2Am+AAmxDcGhLX3WnMfmkNpvSTQU=
@@ -180,7 +176,6 @@ github.com/pion/turn/v2 v2.1.3/go.mod h1:huEpByKKHix2/b9kmTAM3YoX6MKP+/D//0ClgUY
 github.com/pkg/profile v1.4.0/go.mod h1:NWz/XGvpEW1FyYQ7fCx4dqYBLlfTcE+A9FLAkNKqjFE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/sclevine/agouti v3.0.0+incompatible/go.mod h1:b4WX9W9L1sfQKXeJf1mUTLZKJ48R1S7H23Ji7oFO5Bw=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
@@ -215,7 +210,6 @@ golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5y
 golang.org/x/crypto v0.8.0/go.mod h1:mRqEX+O9/h5TFCrQhkgjo2yKi0yYA+9ecGkdQoHrywE=
 golang.org/x/crypto v0.10.0/go.mod h1:o4eNf7Ede1fv+hwOwZsTHl9EsPFO6q6ZvYR8vYfY45I=
 golang.org/x/crypto v0.12.0/go.mod h1:NF0Gs7EO5K4qLn+Ylc+fih8BSTeIjAP05siRnAh98yw=
-golang.org/x/crypto v0.13.0/go.mod h1:y6Z2r+Rw4iayiXXAIxJIDAJ1zMW4yaTpebo8fPOliYc=
 golang.org/x/crypto v0.23.0 h1:dIJU/v2J8Mdglj/8rJ6UUOM3Zc9zLZxVZwwxMooUSAI=
 golang.org/x/crypto v0.23.0/go.mod h1:CKFgDieR+mRhux2Lsu27y0fO304Db0wZe70UKqHu0v8=
 golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
@@ -236,7 +230,6 @@ golang.org/x/net v0.9.0/go.mod h1:d48xBJpPfHeWQsugry2m+kC02ZBRGRgulfHnEXEuWns=
 golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
 golang.org/x/net v0.11.0/go.mod h1:2L/ixqYpgIVXmeoSA/4Lu7BzTG4KIyPIryS4IsOd1oQ=
 golang.org/x/net v0.14.0/go.mod h1:PpSgVXXLK0OxS0F31C1/tv6XNguvCrnXIDrFMspZIUI=
-golang.org/x/net v0.15.0/go.mod h1:idbUs1IY1+zTqbi8yxTbhexhEEk5ur9LInksu6HrEpk=
 golang.org/x/net v0.25.0 h1:d/OCCoBEUq33pjydKrGQhw7IlUPI2Oylr+8qLx49kac=
 golang.org/x/net v0.25.0/go.mod h1:JkAGAh7GEvH74S6FOH42FLoXpXbE/aqXSrIQjXgsiwM=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -268,7 +261,6 @@ golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.9.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.20.0 h1:Od9JTbYCk261bKm4M/mw7AklTlFYIa0bIp9BgSm1S8Y=
 golang.org/x/sys v0.20.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
@@ -280,7 +272,6 @@ golang.org/x/term v0.7.0/go.mod h1:P32HKFT3hSsZrRxla30E9HqToFYAQPCMs/zFMBUFqPY=
 golang.org/x/term v0.8.0/go.mod h1:xPskH00ivmX89bAKVGSKKtLOWNx2+17Eiy94tnKShWo=
 golang.org/x/term v0.9.0/go.mod h1:M6DEAAIenWoTxdKrOltXcmDY3rSplQUkrvaDU5FcQyo=
 golang.org/x/term v0.11.0/go.mod h1:zC9APTIj3jG3FdV/Ons+XE1riIZXG4aZ4GTHiPZJPIU=
-golang.org/x/term v0.12.0/go.mod h1:owVbMEjm3cBLCHdkQu9b1opXd4ETQWc3BhuQGKgXgvU=
 golang.org/x/term v0.20.0 h1:VnkxpohqXaOBYJtBmEppKUG6mXpi+4O6purfc2+sMhw=
 golang.org/x/term v0.20.0/go.mod h1:8UkIAJTvZgivsXaD6/pH6U9ecQzZ45awqEOzuCvwpFY=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -293,7 +284,6 @@ golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/text v0.10.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/text v0.12.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
-golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/text v0.15.0 h1:h1V/4gjBv8v9cjcR6+AR5+/cIYK5N/WAgiv4xlsEtAk=
 golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/time v0.5.0 h1:o7cqy6amK/52YcAKIPlM3a+Fpj35zvRj2TP+e1xFSfk=

internal/protocols/webrtc/incoming_track.go

@@ -69,6 +69,60 @@ var incomingVideoCodecs = []webrtc.RTPCodecParameters{
 }
 
 var incomingAudioCodecs = []webrtc.RTPCodecParameters{
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    3,
+			SDPFmtpLine: "channel_mapping=0,2,1;num_streams=2;coupled_streams=1",
+		},
+		PayloadType: 112,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    4,
+			SDPFmtpLine: "channel_mapping=0,1,2,3;num_streams=2;coupled_streams=2",
+		},
+		PayloadType: 113,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    5,
+			SDPFmtpLine: "channel_mapping=0,4,1,2,3;num_streams=3;coupled_streams=2",
+		},
+		PayloadType: 114,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    6,
+			SDPFmtpLine: "channel_mapping=0,4,1,2,3,5;num_streams=4;coupled_streams=2",
+		},
+		PayloadType: 115,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    7,
+			SDPFmtpLine: "channel_mapping=0,4,1,2,3,5,6;num_streams=4;coupled_streams=4",
+		},
+		PayloadType: 116,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:    mimeMultiopus,
+			ClockRate:   48000,
+			Channels:    8,
+			SDPFmtpLine: "channel_mapping=0,6,1,4,5,2,3,7;num_streams=5;coupled_streams=4",
+		},
+		PayloadType: 117,
+	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
 			MimeType:    webrtc.MimeTypeOpus,
@@ -151,6 +205,12 @@ func newIncomingTrack(
 			PacketizationMode: 1,
 		}
 
+	case strings.ToLower(mimeMultiopus):
+		t.format = &format.Opus{
+			PayloadTyp:   uint8(track.PayloadType()),
+			ChannelCount: int(track.Codec().Channels),
+		}
+
 	case strings.ToLower(webrtc.MimeTypeOpus):
 		t.format = &format.Opus{
 			PayloadTyp: uint8(track.PayloadType()),

internal/protocols/webrtc/outgoing_track.go

@@ -8,6 +8,10 @@ import (
 	"github.com/pion/webrtc/v3"
 )
 
+const (
+	mimeMultiopus = "audio/multiopus"
+)
+
 // OutgoingTrack is a WebRTC outgoing track
 type OutgoingTrack struct {
 	Format format.Format
@@ -56,6 +60,17 @@ func (t *OutgoingTrack) codecParameters() (webrtc.RTPCodecParameters, error) {
 		}, nil
 
 	case *format.Opus:
+		if forma.ChannelCount > 2 {
+			return webrtc.RTPCodecParameters{
+				RTPCodecCapability: webrtc.RTPCodecCapability{
+					MimeType:  mimeMultiopus,
+					ClockRate: 48000,
+					Channels:  uint16(forma.ChannelCount),
+				},
+				PayloadType: 112,
+			}, nil
+		}
+
 		return webrtc.RTPCodecParameters{
 			RTPCodecCapability: webrtc.RTPCodecCapability{
 				MimeType:  webrtc.MimeTypeOpus,

internal/protocols/webrtc/peer_connection.go

@@ -2,6 +2,7 @@ package webrtc
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strconv"
 	"sync"
@@ -276,7 +277,7 @@ func (co *PeerConnection) CreateFullAnswer(
 
 	answer, err := co.wr.CreateAnswer(nil)
 	if err != nil {
-		if err.Error() == "unable to populate media section, RTPSender created with no codecs" {
+		if errors.Is(err, webrtc.ErrSenderWithNoCodecs) {
 			return nil, fmt.Errorf("track codecs are not supported by remote")
 		}
 		return nil, err

internal/servers/webrtc/read_index.html

@@ -107,6 +107,42 @@
 	return ret;
 };
 
+const enableMultichannelOpus = (section) => {
+	let lines = section.split('\r\n');
+
+	lines[0] += " 112";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:112 multiopus/48000/3");
+	lines.splice(lines.length - 1, 0, "a=fmtp:112 channel_mapping=0,2,1;num_streams=2;coupled_streams=1");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:112 transport-cc");
+
+	lines[0] += " 113";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:113 multiopus/48000/4");
+	lines.splice(lines.length - 1, 0, "a=fmtp:113 channel_mapping=0,1,2,3;num_streams=2;coupled_streams=2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:113 transport-cc");
+
+	lines[0] += " 114";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:114 multiopus/48000/5");
+	lines.splice(lines.length - 1, 0, "a=fmtp:114 channel_mapping=0,4,1,2,3;num_streams=3;coupled_streams=2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:114 transport-cc");
+
+	lines[0] += " 115";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:115 multiopus/48000/6");
+	lines.splice(lines.length - 1, 0, "a=fmtp:115 channel_mapping=0,4,1,2,3,5;num_streams=4;coupled_streams=2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:115 transport-cc");
+
+	lines[0] += " 116";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:116 multiopus/48000/7");
+	lines.splice(lines.length - 1, 0, "a=fmtp:116 channel_mapping=0,4,1,2,3,5,6;num_streams=4;coupled_streams=4");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:116 transport-cc");
+
+	lines[0] += " 117";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:117 multiopus/48000/8");
+	lines.splice(lines.length - 1, 0, "a=fmtp:117 channel_mapping=0,6,1,4,5,2,3,7;num_streams=5;coupled_streams=4");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:117 transport-cc");
+
+	return lines.join('\r\n');
+};
+
 const enableStereoOpus = (section) => {
 	let opusPayloadFormat = '';
 	let lines = section.split('\r\n');
@@ -142,7 +178,7 @@
 	for (let i = 0; i < sections.length; i++) {
 		const section = sections[i];
 		if (section.startsWith('audio')) {
-			sections[i] = enableStereoOpus(section);
+			sections[i] = enableMultichannelOpus(enableStereoOpus(section));
 		}
 	}
 
@@ -292,8 +328,8 @@
 	pc.createOffer()
 		.then((offer) => {
 			editOffer(offer);
-			offerData = parseOffer(offer.sdp);
 			pc.setLocalDescription(offer);
+			offerData = parseOffer(offer.sdp);
 			sendOffer(offer);
 		});
 };

internal/servers/webrtc/session.go

@@ -216,10 +216,6 @@ func findAudioTrack(
 
 	if opusFormat != nil {
 		return opusFormat, func(track *webrtc.OutgoingTrack) error {
-			if opusFormat.ChannelCount > 2 {
-				return fmt.Errorf("unsupported Opus channel count: %d", opusFormat.ChannelCount)
-			}
-
 			stream.AddReader(writer, media, opusFormat, func(u unit.Unit) error {
 				for _, pkt := range u.GetRTPPackets() {
 					track.WriteRTP(pkt) //nolint:errcheck