WIP: Draft for NADA BandwidthEstimator

Implements a simple adapter to satisfy the BandwidthEstimator interface
to allow using nada implementation in interceptor.

Author: mengelbart

pkg/nada/bandwidth_estimator.go

@@ -0,0 +1,102 @@
+package nada
+
+import (
+	"math"
+	"time"
+
+	"github.com/pion/interceptor"
+	"github.com/pion/interceptor/internal/cc"
+	"github.com/pion/interceptor/internal/ntp"
+	"github.com/pion/rtcp"
+	"github.com/pion/rtp"
+)
+
+type NadaBandwidthEstimator struct {
+	*cc.FeedbackAdapter
+	*Sender
+	*Receiver
+}
+
+func (e *NadaBandwidthEstimator) AddStream(_ *interceptor.StreamInfo, writer interceptor.RTPWriter) interceptor.RTPWriter {
+	return interceptor.RTPWriterFunc(func(header *rtp.Header, payload []byte, attributes interceptor.Attributes) (int, error) {
+		now := time.Now()
+		if err := e.OnSent(now, header, len(payload), attributes); err != nil {
+			return 0, err
+		}
+		return writer.Write(header, payload, attributes)
+	})
+}
+
+func (e *NadaBandwidthEstimator) WriteRTCP(pkts []rtcp.Packet, _ interceptor.Attributes) error {
+	now := time.Now()
+	var acks []cc.Acknowledgment
+	for _, pkt := range pkts {
+		var feedbackSentTime time.Time
+		switch fb := pkt.(type) {
+		case *rtcp.TransportLayerCC:
+			newAcks, err := e.OnTransportCCFeedback(now, fb)
+			if err != nil {
+				return err
+			}
+			for i, ack := range acks {
+				if i == 0 {
+					feedbackSentTime = ack.Arrival
+					continue
+				}
+				if ack.Arrival.After(feedbackSentTime) {
+					feedbackSentTime = ack.Arrival
+				}
+			}
+			acks = append(acks, newAcks...)
+		case *rtcp.CCFeedbackReport:
+			acks = e.OnRFC8888Feedback(now, fb)
+			feedbackSentTime = ntp.ToTime(uint64(fb.ReportTimestamp) << 16)
+		default:
+			continue
+		}
+
+		feedbackMinRTT := time.Duration(math.MaxInt)
+		for _, ack := range acks {
+			if ack.Arrival.IsZero() {
+				continue
+			}
+			pendingTime := feedbackSentTime.Sub(ack.Arrival)
+			rtt := now.Sub(ack.Departure) - pendingTime
+			feedbackMinRTT = time.Duration(minInt(int(rtt), int(feedbackMinRTT)))
+		}
+		if feedbackMinRTT < math.MaxInt {
+			e.UpdateEstimatedRoundTripTime(feedbackMinRTT)
+		}
+	}
+
+	for _, ack := range acks {
+		e.OnReceiveMediaPacket(ack.Arrival, ack.Departure, ack.SequenceNumber, ack.ECN == rtcp.ECNCE, 8*Bits(ack.Size))
+	}
+
+	e.OnReceiveFeedbackReport(now, e.BuildFeedbackReport())
+	return nil
+}
+
+func (e *NadaBandwidthEstimator) GetTargetBitrate() int {
+	// TODO: What is the buffer len parameter of GetTargetBitrate?
+	return int(e.GetTargetRate(0))
+}
+
+func (e *NadaBandwidthEstimator) OnTargetBitrateChange(f func(bitrate int)) {
+	panic("not implemented")
+}
+
+func (e *NadaBandwidthEstimator) GetStats() map[string]interface{} {
+	panic("not implemented")
+}
+
+func (e *NadaBandwidthEstimator) Close() error {
+	panic("not implemented")
+}
+
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}