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Prevent BWE rampdowns without new loss reports.

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Before this change, UpdateEstimate would repeatedly decrease bitrate
even though there's no fresh corresponding RTCP loss report, triggering
multiple reactions to a single indication of high packet loss.

BUG=webrtc:5101
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1417723005

Cr-Commit-Position: refs/heads/master@{#10374}
This commit is contained in:
pbos
2015-10-22 08:52:20 -07:00
committed by Commit bot
parent 4a859fdce5
commit b7edb88ae2
3 changed files with 78 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.cc
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@ -43,13 +43,14 @@ const size_t kNumUmaRampupMetrics =
}
SendSideBandwidthEstimation::SendSideBandwidthEstimation()
: accumulate_lost_packets_Q8_(0),
accumulate_expected_packets_(0),
: lost_packets_since_last_loss_update_Q8_(0),
expected_packets_since_last_loss_update_(0),
bitrate_(0),
min_bitrate_configured_(kDefaultMinBitrateBps),
max_bitrate_configured_(kDefaultMaxBitrateBps),
last_low_bitrate_log_ms_(-1),
time_last_receiver_block_ms_(0),
has_decreased_since_last_fraction_loss_(false),
time_last_receiver_block_ms_(-1),
last_fraction_loss_(0),
last_round_trip_time_ms_(0),
bwe_incoming_(0),
@ -58,8 +59,7 @@ SendSideBandwidthEstimation::SendSideBandwidthEstimation()
initially_lost_packets_(0),
bitrate_at_2_seconds_kbps_(0),
uma_update_state_(kNoUpdate),
rampup_uma_stats_updated_(kNumUmaRampupMetrics, false) {
}
rampup_uma_stats_updated_(kNumUmaRampupMetrics, false) {}
SendSideBandwidthEstimation::~SendSideBandwidthEstimation() {}
@ -117,21 +117,20 @@ void SendSideBandwidthEstimation::UpdateReceiverBlock(uint8_t fraction_loss,
// Calculate number of lost packets.
const int num_lost_packets_Q8 = fraction_loss * number_of_packets;
// Accumulate reports.
accumulate_lost_packets_Q8_ += num_lost_packets_Q8;
accumulate_expected_packets_ += number_of_packets;
lost_packets_since_last_loss_update_Q8_ += num_lost_packets_Q8;
expected_packets_since_last_loss_update_ += number_of_packets;
// Report loss if the total report is based on sufficiently many packets.
if (accumulate_expected_packets_ >= kLimitNumPackets) {
last_fraction_loss_ =
accumulate_lost_packets_Q8_ / accumulate_expected_packets_;
// Reset accumulators.
accumulate_lost_packets_Q8_ = 0;
accumulate_expected_packets_ = 0;
} else {
// Early return without updating estimate.
// Don't generate a loss rate until it can be based on enough packets.
if (expected_packets_since_last_loss_update_ < kLimitNumPackets)
return;
}
has_decreased_since_last_fraction_loss_ = false;
last_fraction_loss_ = lost_packets_since_last_loss_update_Q8_ /
expected_packets_since_last_loss_update_;
// Reset accumulators.
lost_packets_since_last_loss_update_Q8_ = 0;
expected_packets_since_last_loss_update_ = 0;
}
time_last_receiver_block_ms_ = now_ms;
UpdateEstimate(now_ms);
@ -186,7 +185,9 @@ void SendSideBandwidthEstimation::UpdateEstimate(int64_t now_ms) {
}
UpdateMinHistory(now_ms);
// Only start updating bitrate when receiving receiver blocks.
if (time_last_receiver_block_ms_ != 0) {
// TODO(pbos): Handle the case when no receiver report is received for a very
// long time.
if (time_last_receiver_block_ms_ != -1) {
if (last_fraction_loss_ <= 5) {
// Loss < 2%: Increase rate by 8% of the min bitrate in the last
// kBweIncreaseIntervalMs.
@ -207,12 +208,12 @@ void SendSideBandwidthEstimation::UpdateEstimate(int64_t now_ms) {
} else if (last_fraction_loss_ <= 26) {
// Loss between 2% - 10%: Do nothing.
} else {
// Loss > 10%: Limit the rate decreases to once a kBweDecreaseIntervalMs +
// rtt.
if ((now_ms - time_last_decrease_ms_) >=
(kBweDecreaseIntervalMs + last_round_trip_time_ms_)) {
if (!has_decreased_since_last_fraction_loss_ &&
(now_ms - time_last_decrease_ms_) >=
(kBweDecreaseIntervalMs + last_round_trip_time_ms_)) {
time_last_decrease_ms_ = now_ms;
// Reduce rate:
@ -221,6 +222,7 @@ void SendSideBandwidthEstimation::UpdateEstimate(int64_t now_ms) {
bitrate_ = static_cast<uint32_t>(
(bitrate_ * static_cast<double>(512 - last_fraction_loss_)) /
512.0);
has_decreased_since_last_fraction_loss_ = true;
}
}
}