Implement encoder overshoot detector and rate adjuster.
The overshoot detector uses a simple pacer model to determine an
estimate of how much the encoder is overusing the target bitrate.
This utilization factor can then be adjuster for when configuring the
actual target bitrate.
Spatial layers (simulcast streams) are adjusted separately.
Temporal layers are measured separately, but are combined into a single
utilization factor per spatial layer.
Bug: webrtc:10155
Change-Id: I8ea58dc6c4871e880553d7c22202f11cb2feb216
Reviewed-on: https://webrtc-review.googlesource.com/c/114886
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26573}diff --git a/video/encoder_bitrate_adjuster.h b/video/encoder_bitrate_adjuster.h
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+/*
+ * Copyright (c) 2019 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.
+ */
+
+#ifndef VIDEO_ENCODER_BITRATE_ADJUSTER_H_
+#define VIDEO_ENCODER_BITRATE_ADJUSTER_H_
+
+#include <memory>
+
+#include "api/video/encoded_image.h"
+#include "api/video/video_bitrate_allocation.h"
+#include "api/video_codecs/video_encoder.h"
+#include "video/encoder_overshoot_detector.h"
+
+namespace webrtc {
+
+class EncoderBitrateAdjuster {
+ public:
+ // Size of sliding window used to track overshoot rate.
+ static constexpr int64_t kWindowSizeMs = 3000;
+ // Minimum number of frames since last layout change required to trust the
+ // overshoot statistics. Otherwise falls back to default utilization.
+ // By layout change, we mean any spatial/temporal layer being either enabled
+ // or disabled.
+ static constexpr size_t kMinFramesSinceLayoutChange = 30;
+ // Default utilization, before reliable metrics are available, is set to 20%
+ // overshoot. This is conservative so that badly misbehaving encoders don't
+ // build too much queue at the very start.
+ static constexpr double kDefaultUtilizationFactor = 1.2;
+
+ explicit EncoderBitrateAdjuster(const VideoCodec& codec_settings);
+ ~EncoderBitrateAdjuster();
+
+ // Adjusts the given rate allocation to make it paceable within the target
+ // rates.
+ VideoBitrateAllocation AdjustRateAllocation(
+ const VideoBitrateAllocation& bitrate_allocation,
+ int framerate_fps);
+
+ // Updated overuse detectors with data about the encoder, specifically about
+ // the temporal layer frame rate allocation.
+ void OnEncoderInfo(const VideoEncoder::EncoderInfo& encoder_info);
+
+ // Updates the overuse detectors according to the encoded image size.
+ void OnEncodedFrame(const EncodedImage& encoded_image, int temporal_index);
+
+ void Reset();
+
+ private:
+ VideoBitrateAllocation current_bitrate_allocation_;
+ int current_total_framerate_fps_;
+ // FPS allocation of temporal layers, per spatial layer. Represented as a Q8
+ // fraction; 0 = 0%, 255 = 100%. See VideoEncoder::EncoderInfo.fps_allocation.
+ absl::InlinedVector<uint8_t, kMaxTemporalStreams>
+ current_fps_allocation_[kMaxSpatialLayers];
+
+ // Frames since layout was changed, mean that any spatial or temporal layer
+ // was either disabled or enabled.
+ size_t frames_since_layout_change_;
+ std::unique_ptr<EncoderOvershootDetector>
+ overshoot_detectors_[kMaxSpatialLayers][kMaxTemporalStreams];
+
+ // Minimum bitrates allowed, per spatial layer.
+ uint32_t min_bitrates_bps_[kMaxSpatialLayers];
+};
+
+} // namespace webrtc
+
+#endif // VIDEO_ENCODER_BITRATE_ADJUSTER_H_
