Using SetCodecPrefences to constrain the track type disables negotiation of RTX #2996
Description
In Galene, I'm using SetCodecPreferences to ensure that we negotiate the right codec for a track forwarded to a client. Unfortunately, this has the side effect of disabling RTX.
Here's a full test:
package rtxtest
import (
"strings"
"testing"
"github.com/pion/webrtc/v4"
)
func TestRTX(t *testing.T) {
t.Run("NoSetCodecPreferences", func(t *testing.T) { testRTX(t, false) })
t.Run("SetCodecPreferences", func(t *testing.T) { testRTX(t, true) })
}
func testRTX(t *testing.T, setPreferences bool) {
pc, err := webrtc.NewPeerConnection(webrtc.Configuration{})
if err != nil {
t.Fatalf("NewPeerConnection: %v", err)
}
transceiver, err := pc.AddTransceiverFromKind(
webrtc.RTPCodecTypeVideo,
webrtc.RTPTransceiverInit{
Direction: webrtc.RTPTransceiverDirectionRecvonly,
},
)
if setPreferences {
codec := webrtc.RTPCodecCapability{
"video/vp8", 90000, 0, "", nil,
}
err := transceiver.SetCodecPreferences(
[]webrtc.RTPCodecParameters{
{
RTPCodecCapability: codec,
},
},
)
if err != nil {
t.Errorf("SetCodecPreferences: %v", err)
}
}
if err != nil {
t.Fatalf("AddTransceiverFromKind: %v", err)
}
offer, err := pc.CreateOffer(nil)
if err != nil {
t.Fatalf("CreateOffer: %v", err)
}
if !strings.Contains(offer.SDP, "apt=96") {
t.Errorf("Didn't try to negotiate RTX")
}
}