Bitrate controller for VideoToolbox encoder.

webrtc/video_encoder.h

Index: webrtc/video_encoder.h
diff --git a/webrtc/video_encoder.h b/webrtc/video_encoder.h
index 9e7e4d7040f2fd8401ac934144619612f5fe750a..5e94c87da8dc4cac976d40133243f684d884e792 100644
--- a/webrtc/video_encoder.h
+++ b/webrtc/video_encoder.h
@@ -14,6 +14,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/base/rollingaccumulator.h"
 #include "webrtc/common_types.h"
 #include "webrtc/typedefs.h"
 #include "webrtc/video_frame.h"
@@ -125,6 +126,7 @@ class VideoEncoder {
   virtual void OnDroppedFrame() {}
   virtual int GetTargetFramerate() { return -1; }
   virtual bool SupportsNativeHandle() const { return false; }
+  virtual bool IsHardwareEncoder() const { return false; }
   virtual const char* ImplementationName() const { return "unknown"; }
 };
 
@@ -181,5 +183,70 @@ class VideoEncoderSoftwareFallbackWrapper : public VideoEncoder {
   std::string fallback_implementation_name_;
   EncodedImageCallback* callback_;
 };
+
+// Class used to wrap hardware encoders that don't properly respect their set
+// bitrates. This class will observe input vs output bitrate, and dynamically
+// adjust the bitrate setting on the wrapped encoder so that its output matches
+// the rate we need.
+class HardwareVideoEncoderWrapper : public VideoEncoder {
+ public:
+  HardwareVideoEncoderWrapper(webrtc::VideoEncoder* encoder);
+  virtual ~HardwareVideoEncoderWrapper() {}
+
+  int32_t InitEncode(const VideoCodec* codec_settings,
+                     int32_t number_of_cores,
+                     size_t max_payload_size) override;
+
+  int32_t RegisterEncodeCompleteCallback(
+      EncodedImageCallback* callback) override;
+
+  int32_t Release() override;
+  int32_t Encode(const VideoFrame& frame,
+                 const CodecSpecificInfo* codec_specific_info,
+                 const std::vector<FrameType>* frame_types) override;
+  int32_t SetChannelParameters(uint32_t packet_loss, int64_t rtt) override;
+
+  int32_t SetRates(uint32_t bitrate, uint32_t framerate) override;
+  void OnDroppedFrame() override;
+  int GetTargetFramerate() override;
+  bool SupportsNativeHandle() const override;
+  bool IsHardwareEncoder() const override;
+  const char* ImplementationName() const override;
+
+  // Called when wrapped encoder reports an encoded frame.
+  int32_t OnFrameEncoded(const EncodedImage& encoded_image,
+                         const CodecSpecificInfo* codec_specific_info,
+                         const RTPFragmentationHeader* fragmentation);
+
+ private:
+  static const uint32_t kBitrateUpdateIntervalMs = 2000;  // 2s.
+  static const uint32_t kBitrateTolerancePct = 5;  // 5 percent of original.
+
+  // Updates the bitrate set on the wrapped encoder with relevant penalties.
+  void UpdateBitrate(uint32_t current_time_ms);
+  // Updates the bitrate tracker with a new sample.
+  void UpdateBitrateTracker(size_t frame_size, uint32_t current_time_ms);
+
+  // Wrapped encoder.
+  webrtc::VideoEncoder* const encoder_;
+  // The callback registered with this wrapper.
+  EncodedImageCallback* callback_;
+  // The callback registered with wrapped encoder.
+  rtc::scoped_ptr<EncodedImageCallback> wrapped_callback_;
+  // Simple moving average bitrate estimator.
+  rtc::RollingAccumulator<float> bitrate_tracker_;
+
+  // The bitrate set in SetRates.
+  uint32_t original_bitrate_;
+  // The framerate set in SetRates.
+  uint32_t original_frame_rate_;
+  // The bitrate used to call SetRates on the wrapped encoder.
+  uint32_t adjusted_bitrate_;
+  // The last time we update the bitrate.
+  uint32_t last_bitrate_update_time_ms_;
+  // The timestamp of the last frame received from the wrapped encoder.
+  uint32_t last_frame_time_ms_;
+};
+
 }  // namespace webrtc
 #endif  // WEBRTC_VIDEO_ENCODER_H_