VP8: do not forward RTP packets which payload contains a higher temporal layer than current one. (#1009)

Worker: VP8, do not send frames with temporal layer higher than the current one

Fixes #989


---------

Co-authored-by: Iñaki Baz Castillo <ibc@aliax.net>

Author: jmillan

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### NEXT
 
+- `Worker`: Drop VP8 packets with a higher temporal layer than the current one ([PR #1009](https://github.com/versatica/mediasoup/pull/1009)).
+
 ### 3.15.3
 
 - Node: Expose `Index` interface in `types.indexTypes` or via `import { Index as MediasoupIndex } from 'mediasoup/lib/indexTypes'` ([PR #1485](https://github.com/versatica/mediasoup/pull/1485)).

worker/src/RTC/Codecs/VP8.cpp

@@ -359,7 +359,7 @@ namespace RTC
 			// clang-format off
 			if (
 				this->payloadDescriptor->hasTlIndex &&
-				this->payloadDescriptor->tlIndex > context->GetCurrentTemporalLayer()
+				this->payloadDescriptor->tlIndex == context->GetTargetTemporalLayer()
 			)
 			// clang-format on
 			{
@@ -375,6 +375,12 @@ namespace RTC
 				context->SetCurrentTemporalLayer(context->GetTargetTemporalLayer());
 			}
 
+			// Do not send tlIndex higher than current one.
+			if (this->payloadDescriptor->tlIndex > context->GetCurrentTemporalLayer())
+			{
+				return false;
+			}
+
 			// clang-format off
 			if (
 				this->payloadDescriptor->hasPictureId &&

worker/test/src/RTC/Codecs/TestVP8.cpp

@@ -322,4 +322,68 @@ SCENARIO("process VP8 payload descriptor", "[codecs][vp8]")
 		forwarded = ProcessPacket(context, 1, 0, 1);
 		REQUIRE_FALSE(forwarded);
 	}
+
+	SECTION("old packets with higher temporal layer than current are dropped")
+	{
+		RTC::Codecs::EncodingContext::Params params;
+		params.spatialLayers  = 0;
+		params.temporalLayers = 2;
+		Codecs::VP8::EncodingContext context(params);
+		context.SyncRequired();
+
+		context.SetCurrentTemporalLayer(0);
+		context.SetTargetTemporalLayer(0);
+
+		// Frame 1.
+		auto forwarded = ProcessPacket(context, 1, 0, 0);
+		REQUIRE(forwarded);
+		REQUIRE(forwarded->pictureId == 1);
+		REQUIRE(forwarded->tlIndex == 0);
+		REQUIRE(forwarded->tl0PictureIndex == 1);
+
+		// Frame 2.
+		forwarded = ProcessPacket(context, 2, 0, 0);
+		REQUIRE(forwarded);
+		REQUIRE(forwarded->pictureId == 2);
+		REQUIRE(forwarded->tlIndex == 0);
+		REQUIRE(forwarded->tl0PictureIndex == 1);
+
+		// Frame 3. Old packet with higher temporal layer than current.
+		forwarded = ProcessPacket(context, 0, 0, 1);
+		REQUIRE_FALSE(forwarded);
+		REQUIRE(context.GetCurrentTemporalLayer() == 0);
+	}
+
+	SECTION("packets with higher temporal layer than current are dropped")
+	{
+		RTC::Codecs::EncodingContext::Params params;
+		params.spatialLayers  = 0;
+		params.temporalLayers = 2;
+		Codecs::VP8::EncodingContext context(params);
+		context.SyncRequired();
+
+		context.SetCurrentTemporalLayer(0);
+		context.SetTargetTemporalLayer(0);
+
+		// Frame 1.
+		auto forwarded = ProcessPacket(context, 1, 0, 0);
+		REQUIRE(forwarded);
+		REQUIRE(forwarded->pictureId == 1);
+		REQUIRE(forwarded->tlIndex == 0);
+		REQUIRE(forwarded->tl0PictureIndex == 1);
+
+		// Frame 2.
+		forwarded = ProcessPacket(context, 2, 0, 0);
+		REQUIRE(forwarded);
+		REQUIRE(forwarded->pictureId == 2);
+		REQUIRE(forwarded->tlIndex == 0);
+		REQUIRE(forwarded->tl0PictureIndex == 1);
+
+		context.SetTargetTemporalLayer(2);
+
+		// Frame 3. Old packet with higher temporal layer than current.
+		forwarded = ProcessPacket(context, 3, 0, 1);
+		REQUIRE_FALSE(forwarded);
+		REQUIRE(context.GetCurrentTemporalLayer() == 0);
+	}
 }