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Avoid NACKing after DTX.

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This is done by not adding missing packets to the NACK list if the number of samples per packet is too large.

Bug: webrtc:10178
Change-Id: If46398d6d05ea35f30d7028040d3b808559e950b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231841
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Commit-Queue: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34984}
This commit is contained in:
Jakob Ivarsson
2021-09-13 16:06:28 +02:00
committed by WebRTC LUCI CQ
parent 593b4d550d
commit 018cd3d6fc
3 changed files with 53 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
modules/audio_coding/neteq/nack_tracker.cc
View File

@ -22,7 +22,7 @@ namespace webrtc {
namespace {
const int kDefaultSampleRateKhz = 48;
const int kDefaultPacketSizeMs = 20;
const int kMaxPacketSizeMs = 120;
constexpr char kNackTrackerConfigFieldTrial[] =
"WebRTC-Audio-NetEqNackTrackerConfig";
@ -52,7 +52,6 @@ NackTracker::NackTracker(int nack_threshold_packets)
timestamp_last_decoded_rtp_(0),
any_rtp_decoded_(false),
sample_rate_khz_(kDefaultSampleRateKhz),
samples_per_packet_(sample_rate_khz_ * kDefaultPacketSizeMs),
max_nack_list_size_(kNackListSizeLimit) {}
NackTracker::~NackTracker() = default;
@ -95,33 +94,39 @@ void NackTracker::UpdateLastReceivedPacket(uint16_t sequence_number,
UpdatePacketLossRate(sequence_number - sequence_num_last_received_rtp_ - 1);
UpdateSamplesPerPacket(sequence_number, timestamp);
UpdateList(sequence_number);
UpdateList(sequence_number, timestamp);
sequence_num_last_received_rtp_ = sequence_number;
timestamp_last_received_rtp_ = timestamp;
LimitNackListSize();
}
void NackTracker::UpdateSamplesPerPacket(
absl::optional<int> NackTracker::GetSamplesPerPacket(
uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp) {
uint32_t timestamp_current_received_rtp) const {
uint32_t timestamp_increase =
timestamp_current_received_rtp - timestamp_last_received_rtp_;
uint16_t sequence_num_increase =
sequence_number_current_received_rtp - sequence_num_last_received_rtp_;
samples_per_packet_ = timestamp_increase / sequence_num_increase;
int samples_per_packet = timestamp_increase / sequence_num_increase;
if (samples_per_packet == 0 ||
samples_per_packet > kMaxPacketSizeMs * sample_rate_khz_) {
// Not a valid samples per packet.
return absl::nullopt;
}
return samples_per_packet;
}
void NackTracker::UpdateList(uint16_t sequence_number_current_received_rtp) {
void NackTracker::UpdateList(uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp) {
// Some of the packets which were considered late, now are considered missing.
ChangeFromLateToMissing(sequence_number_current_received_rtp);
if (IsNewerSequenceNumber(sequence_number_current_received_rtp,
sequence_num_last_received_rtp_ + 1))
AddToList(sequence_number_current_received_rtp);
AddToList(sequence_number_current_received_rtp,
timestamp_current_received_rtp);
}
void NackTracker::ChangeFromLateToMissing(
@ -134,16 +139,24 @@ void NackTracker::ChangeFromLateToMissing(
it->second.is_missing = true;
}
uint32_t NackTracker::EstimateTimestamp(uint16_t sequence_num) {
uint32_t NackTracker::EstimateTimestamp(uint16_t sequence_num,
int samples_per_packet) {
uint16_t sequence_num_diff = sequence_num - sequence_num_last_received_rtp_;
return sequence_num_diff * samples_per_packet_ + timestamp_last_received_rtp_;
return sequence_num_diff * samples_per_packet + timestamp_last_received_rtp_;
}
void NackTracker::AddToList(uint16_t sequence_number_current_received_rtp) {
void NackTracker::AddToList(uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp) {
RTC_DCHECK(!any_rtp_decoded_ ||
IsNewerSequenceNumber(sequence_number_current_received_rtp,
sequence_num_last_decoded_rtp_));
absl::optional<int> samples_per_packet = GetSamplesPerPacket(
sequence_number_current_received_rtp, timestamp_current_received_rtp);
if (!samples_per_packet) {
return;
}
// Packets with sequence numbers older than `upper_bound_missing` are
// considered missing, and the rest are considered late.
uint16_t upper_bound_missing =
@ -152,7 +165,7 @@ void NackTracker::AddToList(uint16_t sequence_number_current_received_rtp) {
for (uint16_t n = sequence_num_last_received_rtp_ + 1;
IsNewerSequenceNumber(sequence_number_current_received_rtp, n); ++n) {
bool is_missing = IsNewerSequenceNumber(upper_bound_missing, n);
uint32_t timestamp = EstimateTimestamp(n);
uint32_t timestamp = EstimateTimestamp(n, *samples_per_packet);
NackElement nack_element(TimeToPlay(timestamp), timestamp, is_missing);
nack_list_.insert(nack_list_.end(), std::make_pair(n, nack_element));
}
@ -211,7 +224,6 @@ void NackTracker::Reset() {
timestamp_last_decoded_rtp_ = 0;
any_rtp_decoded_ = false;
sample_rate_khz_ = kDefaultSampleRateKhz;
samples_per_packet_ = sample_rate_khz_ * kDefaultPacketSizeMs;
}
void NackTracker::SetMaxNackListSize(size_t max_nack_list_size) {

23
modules/audio_coding/neteq/nack_tracker.h
View File

@ -17,6 +17,7 @@
#include <map>
#include <vector>
#include "absl/types/optional.h"
#include "modules/include/module_common_types_public.h"
#include "rtc_base/gtest_prod_util.h"
@ -159,22 +160,24 @@ class NackTracker {
// Given the `sequence_number_current_received_rtp` of currently received RTP,
// recognize packets which are not arrive and add to the list.
void AddToList(uint16_t sequence_number_current_received_rtp);
void AddToList(uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp);
// This function subtracts 10 ms of time-to-play for all packets in NACK list.
// This is called when 10 ms elapsed with no new RTP packet decoded.
void UpdateEstimatedPlayoutTimeBy10ms();
// Given the `sequence_number_current_received_rtp` and
// `timestamp_current_received_rtp` of currently received RTP update number
// of samples per packet.
void UpdateSamplesPerPacket(uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp);
// Returns a valid number of samples per packet given the current received
// sequence number and timestamp or nullopt of none could be computed.
absl::optional<int> GetSamplesPerPacket(
uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp) const;
// Given the `sequence_number_current_received_rtp` of currently received RTP
// update the list. That is; some packets will change from late to missing,
// some packets are inserted as missing and some inserted as late.
void UpdateList(uint16_t sequence_number_current_received_rtp);
void UpdateList(uint16_t sequence_number_current_received_rtp,
uint32_t timestamp_current_received_rtp);
// Packets which are considered late for too long (according to
// `nack_threshold_packets_`) are flagged as missing.
@ -186,7 +189,7 @@ class NackTracker {
void LimitNackListSize();
// Estimate timestamp of a missing packet given its sequence number.
uint32_t EstimateTimestamp(uint16_t sequence_number);
uint32_t EstimateTimestamp(uint16_t sequence_number, int samples_per_packet);
// Compute time-to-play given a timestamp.
int64_t TimeToPlay(uint32_t timestamp) const;
@ -215,10 +218,6 @@ class NackTracker {
int sample_rate_khz_; // Sample rate in kHz.
// Number of samples per packet. We update this every time we receive a
// packet, not only for consecutive packets.
int samples_per_packet_;
// A list of missing packets to be retransmitted. Components of the list
// contain the sequence number of missing packets and the estimated time that
// each pack is going to be played out.

15
modules/audio_coding/neteq/nack_tracker_unittest.cc
View File

@ -539,4 +539,19 @@ TEST(NackTrackerTest, PacketLossRateCorrect) {
EXPECT_NEAR(nack->GetPacketLossRateForTest(), 1 << 28, (1 << 30) / 100);
}
TEST(NackTrackerTest, DoNotNackAfterDtx) {
const int kNackListSize = 200;
std::unique_ptr<NackTracker> nack(NackTracker::Create(0));
nack->UpdateSampleRate(kSampleRateHz);
nack->SetMaxNackListSize(kNackListSize);
uint16_t seq_num = 0;
uint32_t timestamp = 0x87654321;
nack->UpdateLastReceivedPacket(seq_num, timestamp);
EXPECT_TRUE(nack->GetNackList(0).empty());
constexpr int kDtxPeriod = 400;
nack->UpdateLastReceivedPacket(seq_num + 2,
timestamp + kDtxPeriod * kSampleRateHz / 1000);
EXPECT_TRUE(nack->GetNackList(0).empty());
}
} // namespace webrtc