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Increase FEC receiver's protected packet queue size.

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- The FEC receiver tracks maximum of 48 media packets at a time, and packet reordering can delay the FEC packet from its protected media packets by more than 48 sequences.
- Such FEC packets do not get purged until much later when newer FEC packets with much higher sequence mark them as old.
- Until that happens, they sit in the receiver queue, wasting CPU cycles.
- If the receiver maintains a larger queue size for the media packets, it increases possibility of having all media packets in the queue, thereby organically purging the FEC packet.
- More importantly, this also increases the efficacy of FEC decode for such packet, since media packets now remain relevant for longer and aid in lost packet recovery.

Bug: webrtc:12656
Change-Id: Id0058df9a23ea31839decf2c37e0670a54c947fc
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215882
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33989}
This commit is contained in:
Harsh Maniar
2021-04-21 01:21:53 -07:00
committed by WebRTC LUCI CQ
parent 256bec8237
commit 085eceb9ec
4 changed files with 24 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
modules/rtp_rtcp/source/flexfec_receiver_unittest.cc
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@ -374,7 +374,8 @@ TEST_F(FlexfecReceiverTest, RecoversFrom50PercentLoss) {
TEST_F(FlexfecReceiverTest, DelayedFecPacketDoesHelp) {
// These values need to be updated if the underlying erasure code
// implementation changes.
const size_t kNumFrames = 48;
// Delay FEC packet by maximum number of media packets tracked by receiver.
const size_t kNumFrames = 192;
const size_t kNumMediaPacketsPerFrame = 1;
const size_t kNumFecPackets = 1;
@ -412,14 +413,16 @@ TEST_F(FlexfecReceiverTest, DelayedFecPacketDoesHelp) {
TEST_F(FlexfecReceiverTest, TooDelayedFecPacketDoesNotHelp) {
// These values need to be updated if the underlying erasure code
// implementation changes.
const size_t kNumFrames = 49;
// Delay FEC packet by one more than maximum number of media packets
// tracked by receiver.
const size_t kNumFrames = 193;
const size_t kNumMediaPacketsPerFrame = 1;
const size_t kNumFecPackets = 1;
PacketList media_packets;
PacketizeFrame(kNumMediaPacketsPerFrame, 0, &media_packets);
PacketizeFrame(kNumMediaPacketsPerFrame, 1, &media_packets);
// Protect two first frames.
// Protect first two frames.
std::list<Packet*> fec_packets = EncodeFec(media_packets, kNumFecPackets);
for (size_t i = 2; i < kNumFrames; ++i) {
PacketizeFrame(kNumMediaPacketsPerFrame, i, &media_packets);
@ -667,11 +670,11 @@ TEST_F(FlexfecReceiverTest, DoesNotDecodeWrappedMediaSequenceUsingOldFec) {
PacketizeFrame(kNumMediaPacketsPerFrame, i, &media_packets);
}
// Receive first (|kFirstFrameNumMediaPackets| + 48) media packets.
// Receive first (|kFirstFrameNumMediaPackets| + 192) media packets.
// Simulate an old FEC packet by separating it from its encoded media
// packets by at least 48 packets.
// packets by at least 192 packets.
auto media_it = media_packets.begin();
for (size_t i = 0; i < (kFirstFrameNumMediaPackets + 48); i++) {
for (size_t i = 0; i < (kFirstFrameNumMediaPackets + 192); i++) {
if (i == 1) {
// Drop the second packet of the first frame.
media_it++;
@ -682,7 +685,7 @@ TEST_F(FlexfecReceiverTest, DoesNotDecodeWrappedMediaSequenceUsingOldFec) {
// Receive FEC packet. Although a protected packet was dropped,
// expect no recovery callback since it is delayed from first frame
// by more than 48 packets.
// by more than 192 packets.
auto fec_it = fec_packets.begin();
std::unique_ptr<Packet> fec_packet_with_rtp_header =
packet_generator_.BuildFlexfecPacket(**fec_it);