versatica · ibc · Jun 26, 2025 · Jun 25, 2025 · Jun 26, 2025 · Jun 26, 2025
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - libuv: Update to v1.51.0 ([PR #1543](https://github.com/versatica/mediasoup/pull/1543)).
 - libsrtp: Update to v3.0.0-beta version in our fork ([PR #1544](https://github.com/versatica/mediasoup/pull/1544)).
+- `XxxxConsumer.cpp`: Only drop packets in RTP sequence manager when they belong to current spatial layer ([PR #1549](https://github.com/versatica/mediasoup/pull/1549)).
 
 ### 3.16.0
 

diff --git a/worker/include/RTC/RtcLogger.hpp b/worker/include/RTC/RtcLogger.hpp
@@ -23,10 +23,8 @@ namespace RTC
 				NOT_A_KEYFRAME,
 				EMPTY_PAYLOAD,
 				SPATIAL_LAYER_MISMATCH,
-				TOO_HIGH_TIMESTAMP_EXTRA_NEEDED,
 				PACKET_PREVIOUS_TO_SPATIAL_LAYER_SWITCH,
 				DROPPED_BY_CODEC,
-				SEND_RTP_STREAM_DISCARDED,
 			};
 
 			static absl::flat_hash_map<DropReason, std::string> dropReason2String;

diff --git a/worker/src/RTC/PipeConsumer.cpp b/worker/src/RTC/PipeConsumer.cpp
@@ -222,12 +222,30 @@ namespace RTC
 		packet->logger.consumerId = this->id;
 #endif
 
+		auto ssrc           = this->mapMappedSsrcSsrc.at(packet->GetSsrc());
+		auto* rtpStream     = this->mapSsrcRtpStream.at(ssrc);
+		auto& syncRequired  = this->mapRtpStreamSyncRequired.at(rtpStream);
+		auto& rtpSeqManager = this->mapRtpStreamRtpSeqManager.at(rtpStream);
+
 		if (!IsActive())
 		{
 #ifdef MS_RTC_LOGGER_RTP
 			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::CONSUMER_INACTIVE);
 #endif
 
+			rtpSeqManager->Drop(packet->GetSequenceNumber());
+
+			return;
+		}
+
+		// If we need to sync, support key frames and this is not a key frame, ignore
+		// the packet.
+		if (syncRequired && this->keyFrameSupported && !packet->IsKeyFrame())
+		{
+			// NOTE: No need to drop the packet in the RTP sequence manager since here
+			// we are blocking all packets but the key frame that would trigger sync
+			// below.
+
 			return;
 		}
 
@@ -243,34 +261,20 @@ namespace RTC
 			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::UNSUPPORTED_PAYLOAD_TYPE);
 #endif
 
-			return;
-		}
-
-		auto ssrc           = this->mapMappedSsrcSsrc.at(packet->GetSsrc());
-		auto* rtpStream     = this->mapSsrcRtpStream.at(ssrc);
-		auto& syncRequired  = this->mapRtpStreamSyncRequired.at(rtpStream);
-		auto& rtpSeqManager = this->mapRtpStreamRtpSeqManager.at(rtpStream);
-
-		// If we need to sync, support key frames and this is not a key frame, ignore
-		// the packet.
-		if (syncRequired && this->keyFrameSupported && !packet->IsKeyFrame())
-		{
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
-#endif
+			rtpSeqManager->Drop(packet->GetSequenceNumber());
 
 			return;
 		}
 
 		// Packets with only padding are not forwarded.
 		if (packet->GetPayloadLength() == 0)
 		{
-			rtpSeqManager->Drop(packet->GetSequenceNumber());
-
 #ifdef MS_RTC_LOGGER_RTP
 			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
 #endif
 
+			rtpSeqManager->Drop(packet->GetSequenceNumber());
+
 			return;
 		}
 

diff --git a/worker/src/RTC/RtcLogger.cpp b/worker/src/RTC/RtcLogger.cpp
@@ -20,10 +20,8 @@ namespace RTC
 			{ RtpPacket::DropReason::NOT_A_KEYFRAME,                          "NotAKeyframe"                       },
 			{ RtpPacket::DropReason::EMPTY_PAYLOAD,                           "EmptyPayload"                       },
 			{ RtpPacket::DropReason::SPATIAL_LAYER_MISMATCH,                  "SpatialLayerMismatch"               },
-			{ RtpPacket::DropReason::TOO_HIGH_TIMESTAMP_EXTRA_NEEDED,         "TooHighTimestampExtraNeeded"        },
 			{ RtpPacket::DropReason::PACKET_PREVIOUS_TO_SPATIAL_LAYER_SWITCH, "PacketPreviousToSpatialLayerSwitch" },
 			{ RtpPacket::DropReason::DROPPED_BY_CODEC,                        "DroppedByCodec"                     },
-			{ RtpPacket::DropReason::SEND_RTP_STREAM_DISCARDED,               "SendRtpStreamDiscarded"             },
 		};
 		// clang-format on
 

diff --git a/worker/src/RTC/SimpleConsumer.cpp b/worker/src/RTC/SimpleConsumer.cpp
@@ -325,6 +325,17 @@ namespace RTC
 			return;
 		}
 
+		// If we need to sync, support key frames and this is not a key frame, ignore
+		// the packet.
+		if (this->syncRequired && this->keyFrameSupported && !packet->IsKeyFrame())
+		{
+			// NOTE: No need to drop the packet in the RTP sequence manager since here
+			// we are blocking all packets but the key frame that would trigger sync
+			// below.
+
+			return;
+		}
+
 		auto payloadType = packet->GetPayloadType();
 
 		// NOTE: This may happen if this Consumer supports just some codecs of those
@@ -342,6 +353,18 @@ namespace RTC
 			return;
 		}
 
+		// Packets with only padding are not forwarded.
+		if (packet->GetPayloadLength() == 0)
+		{
+#ifdef MS_RTC_LOGGER_RTP
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+#endif
+
+			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+
+			return;
+		}
+
 		bool marker;
 
 		// Process the payload if needed. Drop packet if necessary.
@@ -362,31 +385,6 @@ namespace RTC
 			return;
 		}
 
-		// If we need to sync, support key frames and this is not a key frame, ignore
-		// the packet.
-		if (this->syncRequired && this->keyFrameSupported && !packet->IsKeyFrame())
-		{
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
-#endif
-
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
-
-			return;
-		}
-
-		// Packets with only padding are not forwarded.
-		if (packet->GetPayloadLength() == 0)
-		{
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
-#endif
-
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
-
-			return;
-		}
-
 		// Whether this is the first packet after re-sync.
 		const bool isSyncPacket = this->syncRequired;
 

diff --git a/worker/src/RTC/SimulcastConsumer.cpp b/worker/src/RTC/SimulcastConsumer.cpp
@@ -732,24 +732,36 @@ namespace RTC
 		packet->logger.consumerId = this->id;
 #endif
 
+		auto spatialLayer = this->mapMappedSsrcSpatialLayer.at(packet->GetSsrc());
+
 		if (!IsActive())
 		{
+			// Only drop the packet in the RTP sequence manager if it belongs to the
+			// current spatial layer.
+			if (spatialLayer == this->currentSpatialLayer)
+			{
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::CONSUMER_INACTIVE);
+				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::CONSUMER_INACTIVE);
 #endif
 
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+			}
 
 			return;
 		}
 
 		if (this->targetTemporalLayer == -1)
 		{
+			// Only drop the packet in the RTP sequence manager if it belongs to the
+			// current spatial layer.
+			if (spatialLayer == this->currentSpatialLayer)
+			{
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::INVALID_TARGET_LAYER);
+				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::INVALID_TARGET_LAYER);
 #endif
 
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+			}
 
 			return;
 		}
@@ -760,16 +772,22 @@ namespace RTC
 		// in the corresponding Producer.
 		if (!this->supportedCodecPayloadTypes[payloadType])
 		{
-			MS_DEBUG_DEV("payload type not supported [payloadType:%" PRIu8 "]", payloadType);
+			// Only drop the packet in the RTP sequence manager if it belongs to the
+			// current spatial layer.
+			if (spatialLayer == this->currentSpatialLayer)
+			{
+				MS_DEBUG_DEV("payload type not supported [payloadType:%" PRIu8 "]", payloadType);
 
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::UNSUPPORTED_PAYLOAD_TYPE);
+				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::UNSUPPORTED_PAYLOAD_TYPE);
 #endif
 
+				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+			}
+
 			return;
 		}
 
-		auto spatialLayer = this->mapMappedSsrcSpatialLayer.at(packet->GetSsrc());
 		bool shouldSwitchCurrentSpatialLayer{ false };
 
 		// Check whether this is the packet we are waiting for in order to update
@@ -779,11 +797,8 @@ namespace RTC
 			// Ignore if not a key frame.
 			if (!packet->IsKeyFrame())
 			{
-#ifdef MS_RTC_LOGGER_RTP
-				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
-#endif
-
-				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+				// NOTE: Don't drop the packet in the RTP sequence manager since this
+				// packet doesn't belong to the current spatial layer.
 
 				return;
 			}
@@ -798,34 +813,44 @@ namespace RTC
 		// drop it.
 		else if (spatialLayer != this->currentSpatialLayer)
 		{
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::SPATIAL_LAYER_MISMATCH);
-#endif
+			// NOTE: Don't drop the packet in the RTP sequence manager since this
+			// packet doesn't belong to the current spatial layer.
 
 			return;
 		}
 
 		// If we need to sync and this is not a key frame, ignore the packet.
+		// NOTE: syncRequired is true if packet is a key frame of the target spatial
+		// layer or if transport just connected or consumer resumed.
 		if (this->syncRequired && !packet->IsKeyFrame())
 		{
+			// Only drop the packet in the RTP sequence manager if it belongs to the
+			// current spatial layer.
+			if (spatialLayer == this->currentSpatialLayer)
+			{
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
+				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
 #endif
 
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+			}
 
 			return;
 		}
 
-		// If the packet belongs to current spatial layer being sent and packet does
-		// not have payload other than padding, then drop it.
-		if (spatialLayer == this->currentSpatialLayer && packet->GetPayloadLength() == 0)
+		// Packets with only padding are not forwarded.
+		if (packet->GetPayloadLength() == 0)
 		{
+			// Only drop the packet in the RTP sequence manager if it belongs to the
+			// current spatial layer.
+			if (spatialLayer == this->currentSpatialLayer)
+			{
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+				packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
 #endif
 
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+				this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+			}
 
 			return;
 		}
@@ -834,7 +859,7 @@ namespace RTC
 		const bool isSyncPacket = this->syncRequired;
 
 		// Sync sequence number and timestamp if required.
-		if (isSyncPacket && (this->spatialLayerToSync == -1 || this->spatialLayerToSync == spatialLayer))
+		if (isSyncPacket && (this->spatialLayerToSync == -1 || spatialLayer == this->spatialLayerToSync))
 		{
 			if (packet->IsKeyFrame())
 			{
@@ -941,11 +966,8 @@ namespace RTC
 					this->syncRequired       = false;
 					this->spatialLayerToSync = -1;
 
-#ifdef MS_RTC_LOGGER_RTP
-					packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::TOO_HIGH_TIMESTAMP_EXTRA_NEEDED);
-#endif
-
-					this->rtpSeqManager->Drop(packet->GetSequenceNumber());
+					// NOTE: Don't drop the packet in the RTP sequence manager since this
+					// packet doesn't belong to the current spatial layer.
 
 					return;
 				}
@@ -983,7 +1005,10 @@ namespace RTC
 
 		if (!shouldSwitchCurrentSpatialLayer && this->checkingForOldPacketsInSpatialLayer)
 		{
-			// If this is a packet previous to the spatial layer switch, ignore the packet.
+			// If this is a packet previous to the spatial layer switch, ignore the
+			// packet.
+			// NOTE: We drop it in RTP sequence manager because this packet belongs
+			// to current spatial layer.
 			if (SeqManager<uint16_t>::IsSeqLowerThan(
 			      packet->GetSequenceNumber(), this->snReferenceSpatialLayer))
 			{
@@ -1034,6 +1059,8 @@ namespace RTC
 			auto previousTemporalLayer = this->encodingContext->GetCurrentTemporalLayer();
 
 			// Rewrite payload if needed. Drop packet if necessary.
+			// NOTE: We drop it in RTP sequence manager because this packet belongs
+			// to current spatial layer.
 			if (!packet->ProcessPayload(this->encodingContext.get(), marker))
 			{
 #ifdef MS_RTC_LOGGER_RTP
@@ -1112,10 +1139,6 @@ namespace RTC
 			  origSsrc,
 			  origSeq,
 			  origTimestamp);
-
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::SEND_RTP_STREAM_DISCARDED);
-#endif
 		}
 
 		// Restore packet fields.

diff --git a/worker/src/RTC/SvcConsumer.cpp b/worker/src/RTC/SvcConsumer.cpp
@@ -667,6 +667,16 @@ namespace RTC
 			return;
 		}
 
+		// If we need to sync and this is not a key frame, ignore the packet.
+		if (this->syncRequired && !packet->IsKeyFrame())
+		{
+			// NOTE: No need to drop the packet in the RTP sequence manager since here
+			// we are blocking all packets but the key frame that would trigger sync
+			// below.
+
+			return;
+		}
+
 		auto payloadType = packet->GetPayloadType();
 
 		// NOTE: This may happen if this Consumer supports just some codecs of those
@@ -684,18 +694,6 @@ namespace RTC
 			return;
 		}
 
-		// If we need to sync and this is not a key frame, ignore the packet.
-		if (this->syncRequired && !packet->IsKeyFrame())
-		{
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
-#endif
-
-			this->rtpSeqManager->Drop(packet->GetSequenceNumber());
-
-			return;
-		}
-
 		// Packets with only padding are not forwarded.
 		if (packet->GetPayloadLength() == 0)
 		{