Add support for multi codec negotiation

webrtc/src/api/media_engine/media_engine_test.rs

@@ -801,3 +801,77 @@ a=rtpmap:111 opus/48000/2
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_multi_codec_negotiation() -> Result<()> {
+    const OFFER_SDP: &str = "v=0
+o=- 781500112831855234 6 IN IP4 127.0.0.1
+s=-
+t=0 0
+a=group:BUNDLE 0 1 2 3
+a=extmap-allow-mixed
+a=msid-semantic: WMS be0216be-f3d8-40ca-a624-379edf70f1c9
+m=application 53555 UDP/DTLS/SCTP webrtc-datachannel
+a=mid:0
+a=sctp-port:5000
+a=max-message-size:262144
+m=video 9 UDP/TLS/RTP/SAVPF 98
+a=mid:1
+a=sendonly
+a=msid:be0216be-f3d8-40ca-a624-379edf70f1c9 3d032b3b-ffe5-48ec-b783-21375668d1c3
+a=rtcp-mux
+a=rtcp-rsize
+a=rtpmap:98 VP9/90000
+a=rtcp-fb:98 goog-remb
+a=rtcp-fb:98 transport-cc
+a=rtcp-fb:98 ccm fir
+a=rtcp-fb:98 nack
+a=rtcp-fb:98 nack pli
+a=fmtp:98 profile-id=0
+a=rid:q send
+a=rid:h send
+a=simulcast:send q;h
+m=video 9 UDP/TLS/RTP/SAVPF 96
+a=mid:2
+a=sendonly
+a=msid:6ff05509-be96-4ef1-a74f-425e14720983 16d5d7fe-d076-4718-9ca9-ec62b4543727
+a=rtcp-mux
+a=rtcp-rsize
+a=rtpmap:96 VP8/90000
+a=rtcp-fb:96 goog-remb
+a=rtcp-fb:96 transport-cc
+a=rtcp-fb:96 ccm fir
+a=rtcp-fb:96 nack
+a=rtcp-fb:96 nack pli
+a=ssrc:4281768245 cname:JDM9GNMEg+9To6K7
+a=ssrc:4281768245 msid:6ff05509-be96-4ef1-a74f-425e14720983 16d5d7fe-d076-4718-9ca9-ec62b4543727
+";
+    let must_parse = |raw: &str| -> Result<SessionDescription> {
+        let mut reader = Cursor::new(raw.as_bytes());
+        Ok(SessionDescription::unmarshal(&mut reader)?)
+    };
+
+    // "Multi codec negotiation disabled"
+    {
+        let mut m = MediaEngine::default();
+        m.register_default_codecs()?;
+        m.update_from_remote_description(&must_parse(OFFER_SDP)?)
+            .await?;
+        let negotiated_video_codecs = m.negotiated_video_codecs.lock();
+        assert_eq!(negotiated_video_codecs.len(), 1)
+    }
+
+    // "Multi codec negotiation enabled"
+    {
+        let mut m = MediaEngine::default();
+        m.set_multi_codec_negotiation(true);
+        assert!(m.multi_codec_negotiation());
+        m.register_default_codecs()?;
+        m.update_from_remote_description(&must_parse(OFFER_SDP)?)
+            .await?;
+        let negotiated_video_codecs = m.negotiated_video_codecs.lock();
+        assert_eq!(negotiated_video_codecs.len(), 2)
+    }
+
+    Ok(())
+}

webrtc/src/api/media_engine/mod.rs

@@ -88,6 +88,7 @@ pub struct MediaEngine {
     // If we have attempted to negotiate a codec type yet.
     pub(crate) negotiated_video: AtomicBool,
     pub(crate) negotiated_audio: AtomicBool,
+    pub(crate) negotiate_multi_codecs: AtomicBool,
 
     pub(crate) video_codecs: Vec<RTCRtpCodecParameters>,
     pub(crate) audio_codecs: Vec<RTCRtpCodecParameters>,
@@ -335,6 +336,17 @@ impl MediaEngine {
         codecs.push(codec);
     }
 
+    /// set_multi_codec_negotiation enables or disables the negotiation of multiple codecs.
+    pub fn set_multi_codec_negotiation(&mut self, negotiate_multi_codecs: bool) {
+        self.negotiate_multi_codecs
+            .store(negotiate_multi_codecs, Ordering::SeqCst);
+    }
+
+    /// multi_codec_negotiation returns the current state of the negotiation of multiple codecs.
+    pub fn multi_codec_negotiation(&self) -> bool {
+        self.negotiate_multi_codecs.load(Ordering::SeqCst)
+    }
+
     /// register_codec adds codec to the MediaEngine
     /// These are the list of codecs supported by this PeerConnection.
     /// register_codec is not safe for concurrent use.
@@ -653,12 +665,14 @@ impl MediaEngine {
         desc: &SessionDescription,
     ) -> Result<()> {
         for media in &desc.media_descriptions {
-            let typ = if !self.negotiated_audio.load(Ordering::SeqCst)
+            let typ = if (!self.negotiated_audio.load(Ordering::SeqCst)
+                || self.negotiate_multi_codecs.load(Ordering::SeqCst))
                 && media.media_name.media.to_lowercase() == "audio"
             {
                 self.negotiated_audio.store(true, Ordering::SeqCst);
                 RTPCodecType::Audio
-            } else if !self.negotiated_video.load(Ordering::SeqCst)
+            } else if (!self.negotiated_video.load(Ordering::SeqCst)
+                || self.negotiate_multi_codecs.load(Ordering::SeqCst))
                 && media.media_name.media.to_lowercase() == "video"
             {
                 self.negotiated_video.store(true, Ordering::SeqCst);