Fix frozen video in simulcast due to wrong dropping of padding only packets

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Worker: Test, fix buffer overflow ([PR #1419](https://github.com/versatica/mediasoup/pull/1419)).
 - Bump up Meson from 1.3.0 to 1.5.0 ([PR #1424](https://github.com/versatica/mediasoup/pull/1424)).
 - Node: Export new `WorkerObserver`, `ProducerObserver`, etc. TypeScript types ([PR #1430](https://github.com/versatica/mediasoup/pull/1430)).
+- Fix frozen video in simulcast due to wrong dropping of padding only packets ([PR #1431](https://github.com/versatica/mediasoup/pull/1431), thanks to @quanli168).
 
 ### 3.14.8
 

worker/src/RTC/PipeConsumer.cpp

@@ -250,24 +250,24 @@ namespace RTC
 		auto& syncRequired  = this->mapRtpStreamSyncRequired.at(rtpStream);
 		auto& rtpSeqManager = this->mapRtpStreamRtpSeqManager.at(rtpStream);
 
-		// Packets with only padding are not forwarded.
-		if (packet->GetPayloadLength() == 0)
+		// If we need to sync, support key frames and this is not a key frame, ignore
+		// the packet.
+		if (syncRequired && this->keyFrameSupported && !packet->IsKeyFrame())
 		{
-			rtpSeqManager.Drop(packet->GetSequenceNumber());
-
 #ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::NOT_A_KEYFRAME);
 #endif
 
 			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())
+		// 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::NOT_A_KEYFRAME);
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
 #endif
 
 			return;

worker/src/RTC/SimpleConsumer.cpp

@@ -314,18 +314,6 @@ namespace RTC
 			return;
 		}
 
-		// Packets with only padding are not forwarded.
-		if (packet->GetPayloadLength() == 0)
-		{
-			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
-
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
-#endif
-
-			return;
-		}
-
 		auto payloadType = packet->GetPayloadType();
 
 		// NOTE: This may happen if this Consumer supports just some codecs of those
@@ -372,6 +360,18 @@ namespace RTC
 			return;
 		}
 
+		// Packets with only padding are not forwarded.
+		if (packet->GetPayloadLength() == 0)
+		{
+			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
+
+#ifdef MS_RTC_LOGGER_RTP
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+#endif
+
+			return;
+		}
+
 		// Whether this is the first packet after re-sync.
 		const bool isSyncPacket = this->syncRequired;
 

worker/src/RTC/SimulcastConsumer.cpp

@@ -730,18 +730,6 @@ namespace RTC
 			return;
 		}
 
-		// Packets with only padding are not forwarded.
-		if (packet->GetPayloadLength() == 0)
-		{
-			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
-
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
-#endif
-
-			return;
-		}
-
 		if (this->targetTemporalLayer == -1)
 		{
 #ifdef MS_RTC_LOGGER_RTP
@@ -810,6 +798,19 @@ namespace RTC
 			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)
+		{
+			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
+
+#ifdef MS_RTC_LOGGER_RTP
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+#endif
+
+			return;
+		}
+
 		// Whether this is the first packet after re-sync.
 		const bool isSyncPacket = this->syncRequired;
 

worker/src/RTC/SvcConsumer.cpp

@@ -639,18 +639,6 @@ namespace RTC
 			return;
 		}
 
-		// Packets with only padding are not forwarded.
-		if (packet->GetPayloadLength() == 0)
-		{
-			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
-
-#ifdef MS_RTC_LOGGER_RTP
-			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
-#endif
-
-			return;
-		}
-
 		// clang-format off
 		if (
 			this->encodingContext->GetTargetSpatialLayer() == -1 ||
@@ -690,6 +678,18 @@ namespace RTC
 			return;
 		}
 
+		// Packets with only padding are not forwarded.
+		if (packet->GetPayloadLength() == 0)
+		{
+			this->rtpSeqManager.Drop(packet->GetSequenceNumber());
+
+#ifdef MS_RTC_LOGGER_RTP
+			packet->logger.Dropped(RtcLogger::RtpPacket::DropReason::EMPTY_PAYLOAD);
+#endif
+
+			return;
+		}
+
 		// Whether this is the first packet after re-sync.
 		const bool isSyncPacket = this->syncRequired;