dilution bug fix

internal/stream/stream_format.go

@@ -36,8 +36,10 @@ type streamFormat struct {
 	ntpEstimator *ntpestimator.Estimator
 	onDatas      map[*Reader]OnDataFunc
 
-	// For codec-agnostic keyframe detection using RTP-level indicators
+	// For keyframe-only mode
 	lastRTPTimestamp       uint32
+	currentFrameIsKeyframe bool
+	outputSeqNum           uint16
 }
 
 func (sf *streamFormat) initialize() error {
@@ -66,6 +68,84 @@ func (sf *streamFormat) writeUnit(s *Stream, medi *description.Media, u *unit.Un
 	sf.writeUnitInner(s, medi, u)
 }
 
+// isKeyframePacket checks if the first packet of a frame indicates a keyframe
+func (sf *streamFormat) isKeyframePacket(pkt *rtp.Packet) bool {
+	if len(pkt.Payload) == 0 {
+		return false
+	}
+
+	switch sf.format.(type) {
+	case *format.H264:
+		nalType := pkt.Payload[0] & 0x1F
+		switch nalType {
+		case 5: // IDR
+			return true
+		case 7, 8: // SPS, PPS - usually precede IDR in same frame
+			return true
+		case 28, 29: // FU-A, FU-B
+			if len(pkt.Payload) >= 2 {
+				fuNalType := pkt.Payload[1] & 0x1F
+				if fuNalType == 5 { // IDR
+					return true
+				}
+			}
+		case 24: // STAP-A
+			payload := pkt.Payload[1:]
+			for len(payload) > 2 {
+				size := uint16(payload[0])<<8 | uint16(payload[1])
+				payload = payload[2:]
+				if int(size) > len(payload) {
+					break
+				}
+				if size > 0 {
+					innerNalType := payload[0] & 0x1F
+					if innerNalType == 5 || innerNalType == 7 || innerNalType == 8 {
+						return true
+					}
+				}
+				payload = payload[size:]
+			}
+		}
+		return false
+
+	case *format.H265:
+		nalType := (pkt.Payload[0] >> 1) & 0x3F
+		switch nalType {
+		case 19, 20, 21: // IDR_W_RADL, IDR_N_LP, CRA_NUT
+			return true
+		case 32, 33, 34: // VPS, SPS, PPS
+			return true
+		case 49: // FU
+			if len(pkt.Payload) >= 3 {
+				fuNalType := pkt.Payload[2] & 0x3F
+				if fuNalType == 19 || fuNalType == 20 || fuNalType == 21 {
+					return true
+				}
+			}
+		case 48: // AP
+			payload := pkt.Payload[2:]
+			for len(payload) > 2 {
+				size := uint16(payload[0])<<8 | uint16(payload[1])
+				payload = payload[2:]
+				if int(size) > len(payload) || size < 2 {
+					break
+				}
+				innerNalType := (payload[0] >> 1) & 0x3F
+				if innerNalType == 19 || innerNalType == 20 || innerNalType == 21 ||
+					innerNalType == 32 || innerNalType == 33 || innerNalType == 34 {
+					return true
+				}
+				payload = payload[size:]
+			}
+		}
+		return false
+
+	default:
+		// For other codecs, allow all frames
+		return true
+	}
+}
+
 func (sf *streamFormat) writeRTPPacket(
 	s *Stream,
 	medi *description.Media,
@@ -98,40 +178,28 @@ func (sf *streamFormat) writeUnitInner(s *Stream, medi *description.Media, u *un
 
 	// Drop non-keyframes if configured
 	if sf.dropNonKeyframes && medi.Type == description.MediaTypeVideo {
-		// Codec-agnostic keyframe detection using RTP-level indicators:
-		// - Marker bit: indicates the last packet of a frame (complete frame)
-		// - Timestamp change: indicates a new frame
-		// Keyframe heuristic: complete frame (marker bit) on a new timestamp
 		if len(u.RTPPackets) > 0 {
 			firstPkt := u.RTPPackets[0]
 			isNewFrame := firstPkt.Timestamp != sf.lastRTPTimestamp
 
-			// Check if any packet has marker bit set (complete frame)
-			hasMarker := false
-			for _, pkt := range u.RTPPackets {
-				if pkt.Marker {
-					hasMarker = true
-					break
+			// On new frame, check if it's a keyframe by inspecting NAL type
+			if isNewFrame {
+				sf.lastRTPTimestamp = firstPkt.Timestamp
+				sf.currentFrameIsKeyframe = sf.isKeyframePacket(firstPkt)
+			}
+
+			// Drop if not part of a keyframe
+			if !sf.currentFrameIsKeyframe {
+				return
+			}
 		}
 	}
 
-			// Allow complete frames (with marker bit) on new timestamps
-			// Also allow the first frame through (when lastRTPTimestamp is 0)
-			if hasMarker {
-				// Complete frame - allow through if it's a new frame or first frame
-				if isNewFrame || sf.lastRTPTimestamp == 0 {
-					// Update last timestamp when we output a new frame
-					if isNewFrame {
-						sf.lastRTPTimestamp = firstPkt.Timestamp
-					}
-				} else {
-					// Same timestamp as last frame - likely a duplicate or continuation, drop it
-					return
-				}
-			} else {
-				// Incomplete frame (no marker bit) - drop it
-				return
-			}
+	// Rewrite sequence numbers when dropping non-keyframes to ensure continuity
+	if sf.dropNonKeyframes && medi.Type == description.MediaTypeVideo {
+		for _, pkt := range u.RTPPackets {
+			pkt.SequenceNumber = sf.outputSeqNum
+			sf.outputSeqNum++
 		}
 	}