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Fix twcc feedback adapter
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Now only includes packet feedback for packets that were received.
Previously, in flight packets could be considered lost.
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@mengelbart
mengelbart committed Nov 5, 2021
1 parent 57e9724 commit 3767e28
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Showing 3 changed files with 373 additions and 106 deletions.
138 changes: 58 additions & 80 deletions pkg/cc/feedback_adapter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ import (
)

var errMissingTWCCExtension = errors.New("missing transport layer cc header extension")
var errInvalidFeedbackPacket = errors.New("got invalid feedback packet")

// TODO(mathis): make types internal only?

Expand Down Expand Up @@ -52,116 +53,91 @@ func (f *FeedbackAdapter) OnSent(ts time.Time, pkt *rtp.Packet, attributes inter

// OnIncomingTransportCC converts the incoming rtcp.TransportLayerCC to a
// []PacketResult
func (f *FeedbackAdapter) OnIncomingTransportCC(ts time.Time, feedback *rtcp.TransportLayerCC) []types.PacketResult {
func (f *FeedbackAdapter) OnIncomingTransportCC(feedback *rtcp.TransportLayerCC) ([]types.PacketResult, error) {
result := []types.PacketResult{}

baseSequenceNr := feedback.BaseSequenceNumber
sequenceNr := baseSequenceNr
nextRecvDelta := 0
referenceTime := time.Time{}.Add(time.Duration(feedback.ReferenceTime) * 64 * time.Millisecond) // TODO(mathis): Use/save reference time globally?
packetStatusCount := uint16(0)
chunkIndex := 0
deltaIndex := 0
referenceTime := time.Time{}.Add(time.Duration(feedback.ReferenceTime) * 64 * time.Millisecond)

for _, packetChunkInterface := range feedback.PacketChunks {
switch packetChunk := packetChunkInterface.(type) {
for packetStatusCount < feedback.PacketStatusCount {
if chunkIndex >= len(feedback.PacketChunks) || len(feedback.PacketChunks) == 0 {
return nil, errInvalidFeedbackPacket
}
switch packetChunk := feedback.PacketChunks[chunkIndex].(type) {
case *rtcp.RunLengthChunk:
symbol := packetChunk.PacketStatusSymbol
for i := uint16(0); i < packetChunk.RunLength; i++ {
if sent, ok := f.history[sequenceNr]; ok {
var delta time.Duration

switch symbol {
case rtcp.TypeTCCPacketReceivedSmallDelta:
fallthrough
case rtcp.TypeTCCPacketReceivedLargeDelta:
if nextRecvDelta > len(feedback.RecvDeltas)-1 {
if sentPacket, ok := f.history[feedback.BaseSequenceNumber+packetStatusCount]; ok {
if symbol == rtcp.TypeTCCPacketReceivedSmallDelta ||
symbol == rtcp.TypeTCCPacketReceivedLargeDelta {
if deltaIndex >= len(feedback.RecvDeltas) {
// TODO(mathis): Not enough recv deltas for number
// of received packets: warn?
// of received packets: warn or error?
continue
}
recvDelta := feedback.RecvDeltas[nextRecvDelta]
nextRecvDelta++

switch recvDelta.Type {
case rtcp.TypeTCCPacketReceivedSmallDelta:
delta = time.Duration(recvDelta.Delta) * 250 * time.Microsecond

case rtcp.TypeTCCPacketReceivedLargeDelta:
// TODO(mathis): This should not happen: symbol is
// SmallDelta, but recvDelta is largeDelta
// Warn?
delta = time.Duration(recvDelta.Delta) * time.Millisecond

default:
// TODO(mathis): Should not happne, error invalid
// receive delta?
}
receiveTime := referenceTime.Add(delta)
receiveTime := getReceiveTime(referenceTime, feedback.RecvDeltas[deltaIndex])
referenceTime = receiveTime

result = append(result, types.PacketResult{
SentPacket: sent,
SentPacket: sentPacket,
ReceiveTime: receiveTime,
Received: true,
})
delete(f.history, sequenceNr)
deltaIndex++
} else {
result = append(result, types.PacketResult{
SentPacket: sentPacket,
ReceiveTime: time.Time{},
Received: false,
})
}
} else {
// TODO(mathis): got feedback for unsent packet?
}
sequenceNr++
packetStatusCount++
}
chunkIndex++
case *rtcp.StatusVectorChunk:
for _, symbol := range packetChunk.SymbolList {
if sent, ok := f.history[sequenceNr]; ok {
var delta time.Duration

switch symbol {
case rtcp.TypeTCCPacketReceivedSmallDelta:
fallthrough
case rtcp.TypeTCCPacketReceivedLargeDelta:
if nextRecvDelta > len(feedback.RecvDeltas)-1 {
if sentPacket, ok := f.history[feedback.BaseSequenceNumber+packetStatusCount]; ok {
if symbol == rtcp.TypeTCCPacketReceivedSmallDelta ||
symbol == rtcp.TypeTCCPacketReceivedLargeDelta {
if deltaIndex >= len(feedback.RecvDeltas) {
// TODO(mathis): Not enough recv deltas for number
// of received packets: warn?
// of received packets: warn or error?
continue
}
recvDelta := feedback.RecvDeltas[nextRecvDelta]
nextRecvDelta++

switch recvDelta.Type {
case rtcp.TypeTCCPacketReceivedSmallDelta:
delta = time.Duration(recvDelta.Delta) * 250 * time.Microsecond

case rtcp.TypeTCCPacketReceivedLargeDelta:
// TODO(mathis): This should not happen: symbol is
// SmallDelta, but recvDelta is largeDelta
// Warn?
delta = time.Duration(recvDelta.Delta) * time.Millisecond

default:
// TODO(mathis): Should not happne, error invalid
// receive delta?
}
receiveTime := referenceTime.Add(delta)
receiveTime := getReceiveTime(referenceTime, feedback.RecvDeltas[deltaIndex])
referenceTime = receiveTime

result = append(result, types.PacketResult{
SentPacket: sent,
SentPacket: sentPacket,
ReceiveTime: receiveTime,
Received: true,
})
delete(f.history, sequenceNr)
deltaIndex++
} else {
result = append(result, types.PacketResult{
SentPacket: sentPacket,
ReceiveTime: time.Time{},
Received: false,
})
}
}
sequenceNr++
packetStatusCount++
if packetStatusCount >= feedback.PacketStatusCount {
break
}
}
chunkIndex++
}
}
return result, nil
}

for _, v := range sortedKeysUint16(f.history) {
result = append(result, types.PacketResult{
SentPacket: f.history[v],
ReceiveTime: time.Time{},
Received: false,
})
}
return result
// OnIncomingRFC8888 converts the incoming RFC8888 packet to a []PacketResult
func (f *FeedbackAdapter) OnIncomingRFC8888(feedback *rtcp.RawPacket) ([]types.PacketResult, error) {
return nil, nil
}

func sortedKeysUint16(m map[uint16]types.SentPacket) []uint16 {
Expand All @@ -175,7 +151,9 @@ func sortedKeysUint16(m map[uint16]types.SentPacket) []uint16 {
return result
}

// OnIncomingRFC8888 converts the incoming RFC8888 packet to a []PacketResult
func (f *FeedbackAdapter) OnIncomingRFC8888(ts time.Time, feedback *rtcp.RawPacket) []types.PacketResult {
return nil
func getReceiveTime(baseTime time.Time, delta *rtcp.RecvDelta) time.Time {
if delta.Type == rtcp.TypeTCCPacketReceivedSmallDelta {
return baseTime.Add(time.Duration(delta.Delta) * 250 * time.Microsecond)
}
return baseTime.Add(time.Duration(delta.Delta) * time.Millisecond)
}
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