Revert "Fix pacer activity tracking without RTP header extensions (#4831)" (#4833)

This reverts commit 6939fe3c86.

pkg/sfu/pacer/base.go

@@ -85,7 +85,6 @@ func (b *Base) SendPacket(p *Packet) (int, error) {
 		return 0, err
 	}
 
-	b.lastPacketSentAt.Store(mono.UnixNano())
 	return written, nil
 }
 
@@ -104,6 +103,8 @@ func (b *Base) patchRTPHeaderExtensions(p *Packet) error {
 		if err = p.Header.SetExtension(p.AbsSendTimeExtID, absSendTimeBytes); err != nil {
 			return err
 		}
+
+		b.lastPacketSentAt.Store(sendingAt.UnixNano())
 	}
 
 	packetSize := p.HeaderSize + len(p.Payload)
@@ -126,6 +127,8 @@ func (b *Base) patchRTPHeaderExtensions(p *Packet) error {
 		if err = p.Header.SetExtension(p.TransportWideExtID, twccExtBytes); err != nil {
 			return err
 		}
+
+		b.lastPacketSentAt.Store(sendingAt.UnixNano())
 	}
 
 	b.ProbeObserver.RecordPacket(packetSize, p.IsRTX, p.ProbeClusterId, p.IsProbe)

pkg/sfu/pacer/base_test.go

@@ -1,51 +0,0 @@
-// Copyright 2026 LiveKit, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package pacer
-
-import (
-	"testing"
-	"time"
-
-	"github.com/livekit/protocol/logger"
-	"github.com/livekit/protocol/utils/mono"
-	"github.com/pion/rtp"
-	"github.com/stretchr/testify/require"
-)
-
-type testTrackLocalWriter struct{}
-
-func (testTrackLocalWriter) WriteRTP(header *rtp.Header, payload []byte) (int, error) {
-	return header.MarshalSize() + len(payload), nil
-}
-
-func (testTrackLocalWriter) Write(b []byte) (int, error) {
-	return len(b), nil
-}
-
-func TestBaseSendPacketTracksActivityWithoutHeaderExtensions(t *testing.T) {
-	b := NewBase(logger.GetLogger(), nil)
-	b.lastPacketSentAt.Store(mono.UnixNano() - int64(time.Second))
-
-	p := &Packet{
-		Header:      &rtp.Header{Version: 2},
-		HeaderSize: 12,
-		Payload:     []byte{1, 2, 3, 4},
-		WriteStream: testTrackLocalWriter{},
-	}
-
-	_, err := b.SendPacket(p)
-	require.NoError(t, err)
-	require.Less(t, b.TimeSinceLastSentPacket(), 100*time.Millisecond)
-}