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fix: switch VP8 temporal layer up only at a layer sync frame (#4947)

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This commit is contained in:
Raja Subramanian
2026-10-06 09:57:40 +05:30
committed by GitHub
parent b07a53732d
commit 1d7e761aad
2 changed files with 52 additions and 1 deletions
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pkg/sfu/forwarder_test.go
+42
View File
@@ -1933,6 +1933,48 @@ func TestForwarderGetTranslationParamsVideo(t *testing.T) {
require.Equal(t, f.lastSSRC, params.SSRC)
}
func TestForwarderVP8TemporalUpSwitchAtLayerSync(t *testing.T) {
f := newForwarder(testutils.TestVP8Codec, webrtc.RTPCodecTypeVideo)
f.vls.SetCurrent(buffer.VideoLayer{Spatial: 0, Temporal: 0})
f.vls.SetTarget(buffer.VideoLayer{Spatial: 0, Temporal: 2})
// a frame without Y may reference a dropped frame of its layer
steps := []struct {
name string
tid uint8
y bool
expectedThis int32
expectedCurrent int32
}{
{name: "TL2 without Y", tid: 2, expectedThis: 0, expectedCurrent: 0},
{name: "TL1 without Y", tid: 1, expectedThis: 0, expectedCurrent: 0},
{name: "TL0", tid: 0, expectedThis: 0, expectedCurrent: 0},
{name: "TL2 with Y before TL1 sync", tid: 2, y: true, expectedThis: 0, expectedCurrent: 0},
{name: "TL1 with Y", tid: 1, y: true, expectedThis: 1, expectedCurrent: 1},
{name: "TL2 without Y after TL1 switch", tid: 2, expectedThis: 1, expectedCurrent: 1},
{name: "TL2 with Y", tid: 2, y: true, expectedThis: 2, expectedCurrent: 2},
}
for i, step := range steps {
extPkt, err := testutils.GetTestExtPacketVP8(
&testutils.TestExtPacketParams{SequenceNumber: uint16(i), PayloadSize: 20},
&codec.VP8{S: true, I: true, PictureID: uint16(i), T: true, TID: step.tid, Y: step.y},
)
require.NoError(t, err)
require.Equal(t, step.expectedThis, f.vls.SelectTemporal(extPkt), step.name)
require.Equal(t, step.expectedCurrent, f.vls.GetCurrent().Temporal, step.name)
}
// key frame refreshes all buffers, up-switch at it even without Y
f.vls.SetCurrent(buffer.VideoLayer{Spatial: 0, Temporal: 0})
extPkt, err := testutils.GetTestExtPacketVP8(
&testutils.TestExtPacketParams{SequenceNumber: 10, PayloadSize: 20},
&codec.VP8{S: true, I: true, PictureID: 10, T: true, TID: 0, IsKeyFrame: true},
)
require.NoError(t, err)
require.Equal(t, int32(2), f.vls.SelectTemporal(extPkt))
require.Equal(t, int32(2), f.vls.GetCurrent().Temporal)
}
func TestForwarderGetSnTsForPadding(t *testing.T) {
f := newForwarder(testutils.TestVP8Codec, webrtc.RTPCodecTypeVideo)
pkg/sfu/videolayerselector/temporallayerselector/vp8.go
+10 -1
View File
@@ -44,7 +44,16 @@ func (v *VP8) Select(extPkt *buffer.ExtPacket, current int32, target int32) (thi
tid := extPkt.Temporal
if current < target {
if tid > current && tid <= target && vp8.S {
// Up-switch only where nothing dropped can be referenced: a layer sync
// (Y) frame depends only on TL0 (RFC 7741), a key frame refreshes all
// reference buffers. Key frames also cover encoders that never set Y.
// A sync frame raises one layer at a time, the layers in between would
// otherwise forward frames that reference their dropped frames.
switch {
case vp8.IsKeyFrame && tid <= target:
this = target
next = target
case tid == current+1 && tid <= target && vp8.S && vp8.Y:
this = tid
next = tid
}