media_engine: Properly return codec when not negotiated (#595)

* test: media_engine: Add Ambiguous payload type test

Ported from pion

* media_engine: Properly return codec when not negotiated

webrtc/src/api/media_engine/media_engine_test.rs

@@ -123,6 +123,29 @@ a=fmtp:112 minptime=10; useinbandfec=1
         assert_eq!(opus_codec.capability.mime_type, MIME_TYPE_OPUS);
     }
 
+    //"Ambiguous Payload Type"
+    {
+        const OPUS_AMBIGUOUS_PAYLOAD: &str = "v=0
+o=- 4596489990601351948 2 IN IP4 127.0.0.1
+s=-
+t=0 0
+m=audio 9 UDP/TLS/RTP/SAVPF 96
+a=rtpmap:96 opus/48000/2
+a=fmtp:96 minptime=10; useinbandfec=1
+";
+
+        let mut m = MediaEngine::default();
+        m.register_default_codecs()?;
+        m.update_from_remote_description(&must_parse(OPUS_AMBIGUOUS_PAYLOAD)?)
+            .await?;
+
+        assert!(!m.negotiated_video.load(Ordering::SeqCst));
+        assert!(m.negotiated_audio.load(Ordering::SeqCst));
+
+        let (opus_codec, _) = m.get_codec_by_payload(96).await?;
+        assert_eq!(opus_codec.capability.mime_type, MIME_TYPE_OPUS);
+    }
+
     //"Case Insensitive"
     {
         const OPUS_UPCASE: &str = "v=0

webrtc/src/api/media_engine/mod.rs

@@ -465,22 +465,36 @@ impl MediaEngine {
         &self,
         payload_type: PayloadType,
     ) -> Result<(RTCRtpCodecParameters, RTPCodecType)> {
-        {
+        if self.negotiated_video.load(Ordering::SeqCst) {
             let negotiated_video_codecs = self.negotiated_video_codecs.lock();
             for codec in &*negotiated_video_codecs {
                 if codec.payload_type == payload_type {
                     return Ok((codec.clone(), RTPCodecType::Video));
                 }
             }
         }
-        {
+        if self.negotiated_audio.load(Ordering::SeqCst) {
             let negotiated_audio_codecs = self.negotiated_audio_codecs.lock();
             for codec in &*negotiated_audio_codecs {
                 if codec.payload_type == payload_type {
                     return Ok((codec.clone(), RTPCodecType::Audio));
                 }
             }
         }
+        if !self.negotiated_video.load(Ordering::SeqCst) {
+            for codec in &self.video_codecs {
+                if codec.payload_type == payload_type {
+                    return Ok((codec.clone(), RTPCodecType::Video));
+                }
+            }
+        }
+        if !self.negotiated_audio.load(Ordering::SeqCst) {
+            for codec in &self.audio_codecs {
+                if codec.payload_type == payload_type {
+                    return Ok((codec.clone(), RTPCodecType::Audio));
+                }
+            }
+        }
 
         Err(Error::ErrCodecNotFound)
     }