fe0c90501b
These small packets are common for H.264 where the first packet of an IDR contains the parameter sets. BUG=4806 Review URL: https://codereview.webrtc.org/1221943002 Cr-Commit-Position: refs/heads/master@{#9639}
131 lines
4.3 KiB
C++
131 lines
4.3 KiB
C++
/*
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* Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/modules/pacing/bitrate_prober.h"
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#include <assert.h>
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#include <algorithm>
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#include <limits>
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#include <sstream>
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#include "webrtc/system_wrappers/interface/logging.h"
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namespace webrtc {
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namespace {
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int ComputeDeltaFromBitrate(size_t packet_size, int bitrate_bps) {
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assert(bitrate_bps > 0);
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// Compute the time delta needed to send packet_size bytes at bitrate_bps
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// bps. Result is in milliseconds.
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return static_cast<int>(1000ll * static_cast<int64_t>(packet_size) * 8ll /
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bitrate_bps);
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}
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} // namespace
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const size_t BitrateProber::kMinProbePacketSize = 200;
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BitrateProber::BitrateProber()
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: probing_state_(kDisabled),
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packet_size_last_send_(0),
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time_last_send_ms_(-1) {
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}
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void BitrateProber::SetEnabled(bool enable) {
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if (enable) {
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if (probing_state_ == kDisabled) {
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probing_state_ = kAllowedToProbe;
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LOG(LS_INFO) << "Initial bandwidth probing enabled";
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}
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} else {
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probing_state_ = kDisabled;
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LOG(LS_INFO) << "Initial bandwidth probing disabled";
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}
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}
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bool BitrateProber::IsProbing() const {
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return probing_state_ == kProbing;
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}
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void BitrateProber::MaybeInitializeProbe(int bitrate_bps) {
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if (probing_state_ != kAllowedToProbe)
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return;
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probe_bitrates_.clear();
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// Max number of packets used for probing.
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const int kMaxNumProbes = 2;
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const int kPacketsPerProbe = 5;
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const float kProbeBitrateMultipliers[kMaxNumProbes] = {3, 6};
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int bitrates_bps[kMaxNumProbes];
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std::stringstream bitrate_log;
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bitrate_log << "Start probing for bandwidth, bitrates:";
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for (int i = 0; i < kMaxNumProbes; ++i) {
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bitrates_bps[i] = kProbeBitrateMultipliers[i] * bitrate_bps;
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bitrate_log << " " << bitrates_bps[i];
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// We need one extra to get 5 deltas for the first probe.
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if (i == 0)
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probe_bitrates_.push_back(bitrates_bps[i]);
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for (int j = 0; j < kPacketsPerProbe; ++j)
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probe_bitrates_.push_back(bitrates_bps[i]);
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}
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bitrate_log << ", num packets: " << probe_bitrates_.size();
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LOG(LS_INFO) << bitrate_log.str().c_str();
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probing_state_ = kProbing;
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}
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int BitrateProber::TimeUntilNextProbe(int64_t now_ms) {
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if (probing_state_ != kDisabled && probe_bitrates_.empty()) {
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probing_state_ = kWait;
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}
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if (probe_bitrates_.empty()) {
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// No probe started, or waiting for next probe.
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return -1;
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}
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int64_t elapsed_time_ms = now_ms - time_last_send_ms_;
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// We will send the first probe packet immediately if no packet has been
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// sent before.
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int time_until_probe_ms = 0;
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if (packet_size_last_send_ > kMinProbePacketSize &&
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probing_state_ == kProbing) {
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int next_delta_ms = ComputeDeltaFromBitrate(packet_size_last_send_,
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probe_bitrates_.front());
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time_until_probe_ms = next_delta_ms - elapsed_time_ms;
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// There is no point in trying to probe with less than 1 ms between packets
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// as it essentially means trying to probe at infinite bandwidth.
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const int kMinProbeDeltaMs = 1;
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// If we have waited more than 3 ms for a new packet to probe with we will
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// consider this probing session over.
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const int kMaxProbeDelayMs = 3;
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if (next_delta_ms < kMinProbeDeltaMs ||
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time_until_probe_ms < -kMaxProbeDelayMs) {
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// We currently disable probing after the first probe, as we only want
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// to probe at the beginning of a connection. We should set this to
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// kWait if we later want to probe periodically.
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probing_state_ = kWait;
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LOG(LS_INFO) << "Next delta too small, stop probing.";
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time_until_probe_ms = 0;
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}
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}
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return std::max(time_until_probe_ms, 0);
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}
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size_t BitrateProber::RecommendedPacketSize() const {
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return packet_size_last_send_;
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}
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void BitrateProber::PacketSent(int64_t now_ms, size_t packet_size) {
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assert(packet_size > 0);
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packet_size_last_send_ = packet_size;
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time_last_send_ms_ = now_ms;
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if (probing_state_ != kProbing)
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return;
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if (!probe_bitrates_.empty())
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probe_bitrates_.pop_front();
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}
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} // namespace webrtc
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