Bitrate controller for VideoToolbox encoder.

webrtc/video/video_encoder_hardware.cc

+/*
+ *  Copyright 2016 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 <cmath>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/base/timeutils.h"
+#include "webrtc/video_encoder.h"
+
+namespace internal {
+
+class HardwareEncodedImageCallbackWrapper
+    : public webrtc::EncodedImageCallback {
+ public:
+  HardwareEncodedImageCallbackWrapper(
+      webrtc::HardwareVideoEncoderWrapper* encoder)
+      : encoder_(encoder) {
+    RTC_CHECK(encoder_);
+  }
+
+  virtual ~HardwareEncodedImageCallbackWrapper() { encoder_ = nullptr; }
+
+  virtual int32_t Encoded(const webrtc::EncodedImage& encoded_image,
+                          const webrtc::CodecSpecificInfo* codec_specific_info,
+                          const webrtc::RTPFragmentationHeader* fragmentation) {
+    return encoder_->OnFrameEncoded(encoded_image, codec_specific_info,
+                                    fragmentation);
+  }
+
+ private:
+  webrtc::HardwareVideoEncoderWrapper* encoder_;
+};
+
+}  // namespace internal
+
+namespace webrtc {
+
+HardwareVideoEncoderWrapper::HardwareVideoEncoderWrapper(
+    webrtc::VideoEncoder* encoder)
+    : encoder_(encoder),
+      bitrate_tracker_(30 * 20),
+      original_bitrate_(0),
+      original_frame_rate_(0),
+      adjusted_bitrate_(0),
+      last_bitrate_update_time_ms_(0),
+      last_frame_time_ms_(0) {
+  RTC_DCHECK(encoder->IsHardwareEncoder());
+  wrapped_callback_.reset(
+      new internal::HardwareEncodedImageCallbackWrapper(this));
+}
+
+int32_t HardwareVideoEncoderWrapper::InitEncode(
+    const VideoCodec* codec_settings,
+    int32_t number_of_cores,
+    size_t max_payload_size) {
+  return encoder_->InitEncode(codec_settings, number_of_cores,
+                              max_payload_size);
+}
+
+int32_t HardwareVideoEncoderWrapper::RegisterEncodeCompleteCallback(
+    EncodedImageCallback* callback) {
+  callback_ = callback;
+  return encoder_->RegisterEncodeCompleteCallback(wrapped_callback_.get());
+}
+
+int32_t HardwareVideoEncoderWrapper::Release() {
+  return encoder_->Release();
+}
+
+int32_t HardwareVideoEncoderWrapper::Encode(
+    const VideoFrame& frame,
+    const CodecSpecificInfo* codec_specific_info,
+    const std::vector<FrameType>* frame_types) {
+  return encoder_->Encode(frame, codec_specific_info, frame_types);
+}
+
+int32_t HardwareVideoEncoderWrapper::SetChannelParameters(uint32_t packet_loss,
+                                                          int64_t rtt) {
+  return encoder_->SetChannelParameters(packet_loss, rtt);
+}
+
+int32_t HardwareVideoEncoderWrapper::SetRates(uint32_t bitrate,

[pbos-webrtc, 2016/02/03 15:52:22]

This one is permitted to be called often so you should not reset
adjusted_bitrate_ inside.

+                                              uint32_t framerate) {
+  original_bitrate_ = bitrate * 1000;
+  adjusted_bitrate_ = original_bitrate_;
+  original_frame_rate_ = framerate;
+  bitrate_tracker_.Reset();
+  return encoder_->SetRates(bitrate, framerate);
+}
+
+void HardwareVideoEncoderWrapper::OnDroppedFrame() {
+  encoder_->OnDroppedFrame();
+}
+
+int HardwareVideoEncoderWrapper::GetTargetFramerate() {
+  return encoder_->GetTargetFramerate();
+}
+
+bool HardwareVideoEncoderWrapper::SupportsNativeHandle() const {
+  return encoder_->SupportsNativeHandle();
+}
+
+bool HardwareVideoEncoderWrapper::IsHardwareEncoder() const {
+  return encoder_->IsHardwareEncoder();
+}
+
+const char* HardwareVideoEncoderWrapper::ImplementationName() const {
+  return encoder_->ImplementationName();
+}
+
+int32_t HardwareVideoEncoderWrapper::OnFrameEncoded(
+    const EncodedImage& encoded_image,
+    const CodecSpecificInfo* codec_specific_info,
+    const RTPFragmentationHeader* fragmentation) {
+  uint32_t current_time_ms = rtc::Time();
+  UpdateBitrate(current_time_ms);
+  UpdateBitrateTracker(encoded_image._size, current_time_ms);
+  return callback_->Encoded(encoded_image, codec_specific_info, fragmentation);
+}
+
+void HardwareVideoEncoderWrapper::UpdateBitrateTracker(
+    size_t frame_size,
+    uint32_t current_time_ms) {
+  if (last_frame_time_ms_) {
+    RTC_DCHECK_LT(last_frame_time_ms_, current_time_ms);
+    float bitrate_sample =
+        static_cast<float>(frame_size * 8 * 1000) /
+        static_cast<float>(current_time_ms - last_frame_time_ms_);
+    bitrate_tracker_.AddSample(bitrate_sample);
+  }
+  last_frame_time_ms_ = current_time_ms;
+}
+
+void HardwareVideoEncoderWrapper::UpdateBitrate(uint32_t current_time_ms) {
+  if (current_time_ms - last_bitrate_update_time_ms_ <
+      kBitrateUpdateIntervalMs) {
+    return;
+  }
+  if (bitrate_tracker_.count() < 30) {
+    // Wait for some samples before doing anything. Roughly 1s of samples
+    // at 30fps.
+    return;
+  }
+  // Compute exponentially weighted average of bitrate samples.
+  float bitrate = bitrate_tracker_.ComputeWeightedMean(0.17);
+  float error = original_bitrate_ - bitrate;
+
+  // Adjust if we've overshot by any amount or if we've undershot too much.
+  if (bitrate > original_bitrate_ ||
+      error * 100 > kBitrateTolerancePct * original_bitrate_) {
+    // Adjust the bitrate by a fraction of the error.
+    float adjustment = .5 * error;
+    float adjusted_bitrate = original_bitrate_ + adjustment;
+
+    // Clamp the adjustment.
+    float min_bitrate =
+        static_cast<float>(kBitrateTolerancePct * original_bitrate_) / 100.;
+    float max_bitrate =
+        static_cast<float>((100 - kBitrateTolerancePct) * original_bitrate_) /
+        100.;
+    adjusted_bitrate = std::max(adjusted_bitrate, min_bitrate);
+    adjusted_bitrate = std::min(adjusted_bitrate, max_bitrate);
+
+    // Set the adjustment if it's not already set.
+    if (adjusted_bitrate_ != adjusted_bitrate) {
+      encoder_->SetRates(adjusted_bitrate * 1e-3, original_frame_rate_);
+      LOG(LS_INFO) << "Adjusting encoder bitrate:"
+                   << "\n  target_bitrate:" << original_bitrate_
+                   << "\n  actual_bitrate:" << bitrate
+                   << "\n  previous_bitrate:" << adjusted_bitrate_
+                   << "\n  adjusted_bitrate:" << (uint32_t)adjusted_bitrate;
+      adjusted_bitrate_ = adjusted_bitrate;
+    }
+  }
+  last_bitrate_update_time_ms_ = current_time_ms;
+}
+
+}  // namespace webrtc