class AcknowledgedBitrateEstimatorInterface {\n public:\n static std::unique_ptr<AcknowledgedBitrateEstimatorInterface> Create(\n const WebRtcKeyValueConfig* key_value_config);\n virtual ~AcknowledgedBitrateEstimatorInterface();\n\n virtual void IncomingPacketFeedbackVector(\n const std::vector<PacketResult>& packet_feedback_vector) = 0;\n virtual absl::optional<DataRate> bitrate() const = 0;\n virtual absl::optional<DataRate> PeekRate() const = 0;\n virtual void SetAlr(bool in_alr) = 0;\n virtual void SetAlrEndedTime(Timestamp alr_ended_time) = 0;\n};<\/code><\/pre>\nAcknowledgedBitrateEstimator<\/h1>\n
\u786e\u8ba4\u7684\u6bd4\u7279\u7387\u4f30\u7b97\u5668<\/p>\n
class AcknowledgedBitrateEstimator\n : public AcknowledgedBitrateEstimatorInterface {\n public:\n AcknowledgedBitrateEstimator(\n const WebRtcKeyValueConfig* key_value_config,\n std::unique_ptr<BitrateEstimator> bitrate_estimator);\n\n explicit AcknowledgedBitrateEstimator(\n const WebRtcKeyValueConfig* key_value_config);\n ~AcknowledgedBitrateEstimator() override;\n\n void IncomingPacketFeedbackVector(\n const std::vector<PacketResult>& packet_feedback_vector) override;\n absl::optional<DataRate> bitrate() const override;\n absl::optional<DataRate> PeekRate() const override;\n void SetAlr(bool in_alr) override;\n void SetAlrEndedTime(Timestamp alr_ended_time) override;\n\n private:\n absl::optional<Timestamp> alr_ended_time_;\n bool in_alr_;\n std::unique_ptr<BitrateEstimator> bitrate_estimator_;\n};<\/code><\/pre>\nAcknowledgedBitrateEstimator::IncomingPacketFeedbackVector<\/h2>\nvoid AcknowledgedBitrateEstimator::IncomingPacketFeedbackVector(\n const std::vector<PacketResult>& packet_feedback_vector) {\n RTC_DCHECK(std::is_sorted(packet_feedback_vector.begin(),\n packet_feedback_vector.end(),\n PacketResult::ReceiveTimeOrder()));\n \/\/\u904d\u5386\u6570\u636e\u5305\u53cd\u9988\u5217\u8868\n for (const auto& packet : packet_feedback_vector) {\n \/\/\u5f53 ALR \u505c\u6b62\uff0c \u53d1\u9001\u7684\u5305\u7684\u65f6\u95f4\u6bd4 ALR \u7684\u505c\u6b62\u65f6\u95f4\u8fd8\u665a\uff0c\u5219\u671f\u671b\u4e00\u4e2a\u5feb\u901f\u7684\u901f\u7387\u6539\u53d8\n if (alr_ended_time_ && packet.sent_packet.send_time > *alr_ended_time_) {\n bitrate_estimator_->ExpectFastRateChange();\n alr_ended_time_.reset();\n }\n \/\/\u786e\u8ba4\u7684\u4f30\u8ba1\u91cf\u7b49\u4e8e\u53d1\u9001\u7684\u5305\u5927\u5c0f\uff0c \u518d\u52a0\u4e0a\u5148\u524d\u672a\u786e\u8ba4\u7684\u5305\n DataSize acknowledged_estimate = packet.sent_packet.size;\n acknowledged_estimate += packet.sent_packet.prior_unacked_data;\n \/\/\u4ee5\u5305\u7684\u63a5\u6536\u65f6\u95f4\uff0c\u786e\u8ba4\u4f30\u8ba1\u91cf\uff0c\u662f\u5426\u5728 ALR \u4e09\u4e2a\u53c2\u6570\u6765\u4fee\u6b63\u5e26\u5bbd\u4f30\u7b97\u5668\n bitrate_estimator_->Update(packet.receive_time, acknowledged_estimate,\n in_alr_);\n }\n}<\/code><\/pre>\nBitrateEstimator<\/h1>\n
\u8ba1\u7b97\u7ed9\u5b9a\u7684\u786e\u8ba4\u7684\u541e\u5410\u91cf\u7684\u8d1d\u53f6\u65af\u4f30\u8ba1\u503c\uff0c\u5176\u4e2d\u5305\u542b\u5230\u8fbe\u65f6\u95f4\u548c\u6709\u6548\u8d1f\u8f7d\u5927\u5c0f\u3002\u4e0e\u5f53\u524d\u4f30\u8ba1\u503c\u76f8\u5dee\u751a\u8fdc\u6216\u57fa\u4e8e\u5c11\u91cf\u6570\u636e\u5305\u7684\u6837\u672c\u6743\u91cd\u8f83\u5c0f\uff0c\u56e0\u4e3a\u5b83\u4eec\u88ab\u8ba4\u4e3a\u66f4\u6709\u53ef\u80fd\u662f\u7531\u4e0e\u62e5\u585e\u65e0\u5173\u7684\u5ef6\u8fdf\u5cf0\u503c\u5f15\u8d77\u7684\u3002<\/p>\n
\/\/ Computes a bayesian estimate of the throughput given acks containing\n\/\/ the arrival time and payload size. Samples which are far from the current\n\/\/ estimate or are based on few packets are given a smaller weight, as they\n\/\/ are considered to be more likely to have been caused by, e.g., delay spikes\n\/\/ unrelated to congestion.\nclass BitrateEstimator {\n public:\n explicit BitrateEstimator(const WebRtcKeyValueConfig* key_value_config);\n virtual ~BitrateEstimator();\n virtual void Update(Timestamp at_time, DataSize amount, bool in_alr);\n\n virtual absl::optional<DataRate> bitrate() const;\n absl::optional<DataRate> PeekRate() const;\n\n virtual void ExpectFastRateChange();\n\n private:\n float UpdateWindow(int64_t now_ms,\n int bytes,\n int rate_window_ms,\n bool* is_small_sample);\n int sum_;\n FieldTrialConstrained<int> initial_window_ms_;\n FieldTrialConstrained<int> noninitial_window_ms_;\n FieldTrialParameter<double> uncertainty_scale_;\n FieldTrialParameter<double> uncertainty_scale_in_alr_;\n FieldTrialParameter<double> small_sample_uncertainty_scale_;\n FieldTrialParameter<DataSize> small_sample_threshold_;\n FieldTrialParameter<DataRate> uncertainty_symmetry_cap_;\n FieldTrialParameter<DataRate> estimate_floor_;\n int64_t current_window_ms_;\n int64_t prev_time_ms_;\n float bitrate_estimate_kbps_;\n float bitrate_estimate_var_;\n};\n<\/code><\/pre>\nBitrateEstimator::Update<\/h2>\n
\u8fd9\u91cc\u7528\u5230\u4e86\u8d1d\u53f6\u65af\u4f30\u8ba1, \u5e26\u5bbd\u4f30\u7b97\u51c6\u786e\u7684\u6982\u7387\u662f\u968f\u7740\u5b9e\u9645\u7684\u4f20\u8f93\u6bd4\u7279\u7387\u7684\u53d8\u5316\u800c\u8c03\u6574\u7684
\n![\"file\"](\"https:\/\/www.fanyamin.com\/wordpress\/wp-content\/uploads\/2022\/03\/image-1646840749447.png\")
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\u73b0\u8c61 B \u51fa\u73b0\u7684\u60c5\u51b5\u4e0b\u4e8b\u4ef6 A \u53d1\u751f\u7684\u6982\u7387, \u7b49\u4e8e\u4e8b\u4ef6 A \u53d1\u751f\u65f6\u73b0\u8c61 B \u51fa\u73b0\u7684\u6982\u7387,\u4e58\u4ee5\u4e8b\u4ef6 A \u53d1\u751f\u7684\u6982\u7387, \u518d\u9664\u4ee5\u73b0\u8c61 B \u51fa\u73b0\u7684\u6982\u7387<\/p>\n
\nvoid BitrateEstimator::Update(Timestamp at_time, DataSize amount, bool in_alr) {\n int rate_window_ms = noninitial_window_ms_.Get();\n \/\/ We use a larger window at the beginning to get a more stable sample that\n \/\/ we can use to initialize the estimate.\n if (bitrate_estimate_kbps_ < 0.f)\n rate_window_ms = initial_window_ms_.Get();\n bool is_small_sample = false;\n float bitrate_sample_kbps = UpdateWindow(at_time.ms(), amount.bytes(),\n rate_window_ms, &is_small_sample);\n if (bitrate_sample_kbps < 0.0f)\n return;\n if (bitrate_estimate_kbps_ < 0.0f) {\n \/\/ This is the very first sample we get. Use it to initialize the estimate.\n bitrate_estimate_kbps_ = bitrate_sample_kbps;\n return;\n }\n \/\/ Optionally use higher uncertainty for very small samples to avoid dropping\n \/\/ estimate and for samples obtained in ALR.\n float scale = uncertainty_scale_;\n if (is_small_sample && bitrate_sample_kbps < bitrate_estimate_kbps_) {\n scale = small_sample_uncertainty_scale_;\n } else if (in_alr && bitrate_sample_kbps < bitrate_estimate_kbps_) {\n \/\/ Optionally use higher uncertainty for samples obtained during ALR.\n scale = uncertainty_scale_in_alr_;\n }\n \/\/ Define the sample uncertainty as a function of how far away it is from the\n \/\/ current estimate. With low values of uncertainty_symmetry_cap_ we add more\n \/\/ uncertainty to increases than to decreases. For higher values we approach\n \/\/ symmetry.\n float sample_uncertainty =\n scale * std::abs(bitrate_estimate_kbps_ - bitrate_sample_kbps) \/\n (bitrate_estimate_kbps_ +\n std::min(bitrate_sample_kbps,\n uncertainty_symmetry_cap_.Get().kbps<float>()));\n\n float sample_var = sample_uncertainty * sample_uncertainty;\n \/\/ Update a bayesian estimate of the rate, weighting it lower if the sample\n \/\/ uncertainty is large.\n \/\/ The bitrate estimate uncertainty is increased with each update to model\n \/\/ that the bitrate changes over time.\n float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f;\n bitrate_estimate_kbps_ = (sample_var * bitrate_estimate_kbps_ +\n pred_bitrate_estimate_var * bitrate_sample_kbps) \/\n (sample_var + pred_bitrate_estimate_var);\n bitrate_estimate_kbps_ =\n std::max(bitrate_estimate_kbps_, estimate_floor_.Get().kbps<float>());\n bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var \/\n (sample_var + pred_bitrate_estimate_var);\n BWE_TEST_LOGGING_PLOT(1, "acknowledged_bitrate", at_time.ms(),\n bitrate_estimate_kbps_ * 1000);\n}\n<\/code><\/pre>\nUpdateWindow<\/h2>\n
\u4fee\u6539\u5f53\u524d\u65f6\u95f4\u6240\u5728\u7684\u6ed1\u52a8\u7a97\u53e3\u7684\u4f20\u8f93\u5b57\u8282\u6570<\/p>\n
\nfloat BitrateEstimator::UpdateWindow(int64_t now_ms,\n int bytes,\n int rate_window_ms,\n bool* is_small_sample) {\n RTC_DCHECK(is_small_sample != nullptr);\n \/\/ Reset if time moves backwards.\n if (now_ms < prev_time_ms_) {\n prev_time_ms_ = -1;\n sum_ = 0;\n current_window_ms_ = 0;\n }\n if (prev_time_ms_ >= 0) {\n current_window_ms_ += now_ms - prev_time_ms_;\n \/\/ Reset if nothing has been received for more than a full window.\n if (now_ms - prev_time_ms_ > rate_window_ms) {\n sum_ = 0;\n current_window_ms_ %= rate_window_ms;\n }\n }\n prev_time_ms_ = now_ms;\n float bitrate_sample = -1.0f;\n if (current_window_ms_ >= rate_window_ms) {\n *is_small_sample = sum_ < small_sample_threshold_->bytes();\n bitrate_sample = 8.0f * sum_ \/ static_cast<float>(rate_window_ms);\n current_window_ms_ -= rate_window_ms;\n sum_ = 0;\n }\n sum_ += bytes;\n return bitrate_sample;\n}\n\nabsl::optional<DataRate> BitrateEstimator::bitrate() const {\n if (bitrate_estimate_kbps_ < 0.f)\n return absl::nullopt;\n return DataRate::KilobitsPerSec(bitrate_estimate_kbps_);\n}\n\nabsl::optional<DataRate> BitrateEstimator::PeekRate() const {\n if (current_window_ms_ > 0)\n return DataSize::Bytes(sum_) \/ TimeDelta::Millis(current_window_ms_);\n return absl::nullopt;\n}<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"AcknowledgedBitrateEstimatorInterface \u786e\u8ba4\u7684\u6bd4\u7279\u7387\u4f30\u7b97\u5668\u63a5\u53e3 class AcknowledgedBitrateEstimatorInterface { public: static std::unique_ptr<AcknowledgedBitrateEstimatorInterface> Create( const WebRtcKeyValueConfig* key_value_config); virtual ~AcknowledgedBitrateEstimatorInterface(); virtual void IncomingPacketFeedbackVector( const std::vector<PacketResult>& packet_feedback_vector) = 0; virtual absl::optional<DataRate> bitrate() const = 0; virtual absl::optional<DataRate> PeekRate() const = 0; virtual void SetAlr(bool in_alr) = 0; virtual void SetAlrEndedTime(Timestamp alr_ended_time) = 0; }; AcknowledgedBitrateEstimator \u786e\u8ba4\u7684\u6bd4\u7279\u7387\u4f30\u7b97\u5668 class AcknowledgedBitrateEstimator : public AcknowledgedBitrateEstimatorInterface { […] →Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-543","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/543"}],"collection":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=543"}],"version-history":[{"count":8,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/543\/revisions"}],"predecessor-version":[{"id":552,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/543\/revisions\/552"}],"wp:attachment":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=543"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=543"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=543"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}