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/*
* Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "webrtc/modules/pacing/bitrate_prober.h"
#include <assert.h>
#include <algorithm>
#include <limits>
#include <sstream>
#include "webrtc/modules/pacing/include/paced_sender.h"
#include "webrtc/system_wrappers/include/logging.h"
namespace webrtc {
namespace {
int ComputeDeltaFromBitrate(size_t packet_size, int bitrate_bps) {
assert(bitrate_bps > 0);
// Compute the time delta needed to send packet_size bytes at bitrate_bps
// bps. Result is in milliseconds.
return static_cast<int>(1000ll * static_cast<int64_t>(packet_size) * 8ll /
bitrate_bps);
}
} // namespace
BitrateProber::BitrateProber()
: probing_state_(kDisabled),
packet_size_last_send_(0),
time_last_send_ms_(-1) {
}
void BitrateProber::SetEnabled(bool enable) {
if (enable) {
if (probing_state_ == kDisabled) {
probing_state_ = kAllowedToProbe;
LOG(LS_INFO) << "Initial bandwidth probing enabled";
}
} else {
probing_state_ = kDisabled;
LOG(LS_INFO) << "Initial bandwidth probing disabled";
}
}
bool BitrateProber::IsProbing() const {
return probing_state_ == kProbing;
}
void BitrateProber::MaybeInitializeProbe(int bitrate_bps) {
if (probing_state_ != kAllowedToProbe)
return;
probe_bitrates_.clear();
// Max number of packets used for probing.
const int kMaxNumProbes = 2;
const int kPacketsPerProbe = 5;
const float kProbeBitrateMultipliers[kMaxNumProbes] = {3, 6};
int bitrates_bps[kMaxNumProbes];
std::stringstream bitrate_log;
bitrate_log << "Start probing for bandwidth, bitrates:";
for (int i = 0; i < kMaxNumProbes; ++i) {
bitrates_bps[i] = kProbeBitrateMultipliers[i] * bitrate_bps;
bitrate_log << " " << bitrates_bps[i];
// We need one extra to get 5 deltas for the first probe.
if (i == 0)
probe_bitrates_.push_back(bitrates_bps[i]);
for (int j = 0; j < kPacketsPerProbe; ++j)
probe_bitrates_.push_back(bitrates_bps[i]);
}
bitrate_log << ", num packets: " << probe_bitrates_.size();
LOG(LS_INFO) << bitrate_log.str().c_str();
probing_state_ = kProbing;
}
int BitrateProber::TimeUntilNextProbe(int64_t now_ms) {
if (probing_state_ != kDisabled && probe_bitrates_.empty()) {
probing_state_ = kWait;
}
if (probe_bitrates_.empty()) {
// No probe started, or waiting for next probe.
return -1;
}
int64_t elapsed_time_ms = now_ms - time_last_send_ms_;
// We will send the first probe packet immediately if no packet has been
// sent before.
int time_until_probe_ms = 0;
if (packet_size_last_send_ > PacedSender::kMinProbePacketSize &&
probing_state_ == kProbing) {
int next_delta_ms = ComputeDeltaFromBitrate(packet_size_last_send_,
probe_bitrates_.front());
time_until_probe_ms = next_delta_ms - elapsed_time_ms;
// There is no point in trying to probe with less than 1 ms between packets
// as it essentially means trying to probe at infinite bandwidth.
const int kMinProbeDeltaMs = 1;
// If we have waited more than 3 ms for a new packet to probe with we will
// consider this probing session over.
const int kMaxProbeDelayMs = 3;
if (next_delta_ms < kMinProbeDeltaMs ||
time_until_probe_ms < -kMaxProbeDelayMs) {
// We currently disable probing after the first probe, as we only want
// to probe at the beginning of a connection. We should set this to
// kWait if we later want to probe periodically.
probing_state_ = kWait;
LOG(LS_INFO) << "Next delta too small, stop probing.";
time_until_probe_ms = 0;
}
}
return std::max(time_until_probe_ms, 0);
}
size_t BitrateProber::RecommendedPacketSize() const {
return packet_size_last_send_;
}
void BitrateProber::PacketSent(int64_t now_ms, size_t packet_size) {
assert(packet_size > 0);
packet_size_last_send_ = packet_size;
time_last_send_ms_ = now_ms;
if (probing_state_ != kProbing)
return;
if (!probe_bitrates_.empty())
probe_bitrates_.pop_front();
}
} // namespace webrtc
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