Reland of Split iOS sdk in to separate targets

webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm

+/*
+ *  Copyright (c) 2015 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 "webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.h"
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#if defined(WEBRTC_IOS)
+#import "WebRTC/UIDevice+RTCDevice.h"
+#include "Common/RTCUIApplication.h"
+#endif
+#include "libyuv/convert_from.h"
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/common_video/h264/profile_level_id.h"
+#include "webrtc/sdk/objc/Framework/Classes/Video/corevideo_frame_buffer.h"
+#include "webrtc/sdk/objc/Framework/Classes/VideoToolbox/nalu_rewriter.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace internal {
+
+// The ratio between kVTCompressionPropertyKey_DataRateLimits and
+// kVTCompressionPropertyKey_AverageBitRate. The data rate limit is set higher
+// than the average bit rate to avoid undershooting the target.
+const float kLimitToAverageBitRateFactor = 1.5f;
+// These thresholds deviate from the default h264 QP thresholds, as they
+// have been found to work better on devices that support VideoToolbox
+const int kLowH264QpThreshold = 28;
+const int kHighH264QpThreshold = 39;
+
+// Convenience function for creating a dictionary.
+inline CFDictionaryRef CreateCFDictionary(CFTypeRef* keys,
+                                          CFTypeRef* values,
+                                          size_t size) {
+  return CFDictionaryCreate(kCFAllocatorDefault, keys, values, size,
+                            &kCFTypeDictionaryKeyCallBacks,
+                            &kCFTypeDictionaryValueCallBacks);
+}
+
+// Copies characters from a CFStringRef into a std::string.
+std::string CFStringToString(const CFStringRef cf_string) {
+  RTC_DCHECK(cf_string);
+  std::string std_string;
+  // Get the size needed for UTF8 plus terminating character.
+  size_t buffer_size =
+      CFStringGetMaximumSizeForEncoding(CFStringGetLength(cf_string),
+                                        kCFStringEncodingUTF8) +
+      1;
+  std::unique_ptr<char[]> buffer(new char[buffer_size]);
+  if (CFStringGetCString(cf_string, buffer.get(), buffer_size,
+                         kCFStringEncodingUTF8)) {
+    // Copy over the characters.
+    std_string.assign(buffer.get());
+  }
+  return std_string;
+}
+
+// Convenience function for setting a VT property.
+void SetVTSessionProperty(VTSessionRef session,
+                          CFStringRef key,
+                          int32_t value) {
+  CFNumberRef cfNum =
+      CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &value);
+  OSStatus status = VTSessionSetProperty(session, key, cfNum);
+  CFRelease(cfNum);
+  if (status != noErr) {
+    std::string key_string = CFStringToString(key);
+    LOG(LS_ERROR) << "VTSessionSetProperty failed to set: " << key_string
+                  << " to " << value << ": " << status;
+  }
+}
+
+// Convenience function for setting a VT property.
+void SetVTSessionProperty(VTSessionRef session,
+                          CFStringRef key,
+                          uint32_t value) {
+  int64_t value_64 = value;
+  CFNumberRef cfNum =
+      CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt64Type, &value_64);
+  OSStatus status = VTSessionSetProperty(session, key, cfNum);
+  CFRelease(cfNum);
+  if (status != noErr) {
+    std::string key_string = CFStringToString(key);
+    LOG(LS_ERROR) << "VTSessionSetProperty failed to set: " << key_string
+                  << " to " << value << ": " << status;
+  }
+}
+
+// Convenience function for setting a VT property.
+void SetVTSessionProperty(VTSessionRef session, CFStringRef key, bool value) {
+  CFBooleanRef cf_bool = (value) ? kCFBooleanTrue : kCFBooleanFalse;
+  OSStatus status = VTSessionSetProperty(session, key, cf_bool);
+  if (status != noErr) {
+    std::string key_string = CFStringToString(key);
+    LOG(LS_ERROR) << "VTSessionSetProperty failed to set: " << key_string
+                  << " to " << value << ": " << status;
+  }
+}
+
+// Convenience function for setting a VT property.
+void SetVTSessionProperty(VTSessionRef session,
+                          CFStringRef key,
+                          CFStringRef value) {
+  OSStatus status = VTSessionSetProperty(session, key, value);
+  if (status != noErr) {
+    std::string key_string = CFStringToString(key);
+    std::string val_string = CFStringToString(value);
+    LOG(LS_ERROR) << "VTSessionSetProperty failed to set: " << key_string
+                  << " to " << val_string << ": " << status;
+  }
+}
+
+// Struct that we pass to the encoder per frame to encode. We receive it again
+// in the encoder callback.
+struct FrameEncodeParams {
+  FrameEncodeParams(webrtc::H264VideoToolboxEncoder* e,
+                    const webrtc::CodecSpecificInfo* csi,
+                    int32_t w,
+                    int32_t h,
+                    int64_t rtms,
+                    uint32_t ts,
+                    webrtc::VideoRotation r)
+      : encoder(e),
+        width(w),
+        height(h),
+        render_time_ms(rtms),
+        timestamp(ts),
+        rotation(r) {
+    if (csi) {
+      codec_specific_info = *csi;
+    } else {
+      codec_specific_info.codecType = webrtc::kVideoCodecH264;
+    }
+  }
+
+  webrtc::H264VideoToolboxEncoder* encoder;
+  webrtc::CodecSpecificInfo codec_specific_info;
+  int32_t width;
+  int32_t height;
+  int64_t render_time_ms;
+  uint32_t timestamp;
+  webrtc::VideoRotation rotation;
+};
+
+// We receive I420Frames as input, but we need to feed CVPixelBuffers into the
+// encoder. This performs the copy and format conversion.
+// TODO(tkchin): See if encoder will accept i420 frames and compare performance.
+bool CopyVideoFrameToPixelBuffer(
+    const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& frame,
+    CVPixelBufferRef pixel_buffer) {
+  RTC_DCHECK(pixel_buffer);
+  RTC_DCHECK_EQ(CVPixelBufferGetPixelFormatType(pixel_buffer),
+                kCVPixelFormatType_420YpCbCr8BiPlanarFullRange);
+  RTC_DCHECK_EQ(CVPixelBufferGetHeightOfPlane(pixel_buffer, 0),
+                static_cast<size_t>(frame->height()));
+  RTC_DCHECK_EQ(CVPixelBufferGetWidthOfPlane(pixel_buffer, 0),
+                static_cast<size_t>(frame->width()));
+
+  CVReturn cvRet = CVPixelBufferLockBaseAddress(pixel_buffer, 0);
+  if (cvRet != kCVReturnSuccess) {
+    LOG(LS_ERROR) << "Failed to lock base address: " << cvRet;
+    return false;
+  }
+  uint8_t* dst_y = reinterpret_cast<uint8_t*>(
+      CVPixelBufferGetBaseAddressOfPlane(pixel_buffer, 0));
+  int dst_stride_y = CVPixelBufferGetBytesPerRowOfPlane(pixel_buffer, 0);
+  uint8_t* dst_uv = reinterpret_cast<uint8_t*>(
+      CVPixelBufferGetBaseAddressOfPlane(pixel_buffer, 1));
+  int dst_stride_uv = CVPixelBufferGetBytesPerRowOfPlane(pixel_buffer, 1);
+  // Convert I420 to NV12.
+  int ret = libyuv::I420ToNV12(
+      frame->DataY(), frame->StrideY(),
+      frame->DataU(), frame->StrideU(),
+      frame->DataV(), frame->StrideV(),
+      dst_y, dst_stride_y, dst_uv, dst_stride_uv,
+      frame->width(), frame->height());
+  CVPixelBufferUnlockBaseAddress(pixel_buffer, 0);
+  if (ret) {
+    LOG(LS_ERROR) << "Error converting I420 VideoFrame to NV12 :" << ret;
+    return false;
+  }
+  return true;
+}
+
+CVPixelBufferRef CreatePixelBuffer(CVPixelBufferPoolRef pixel_buffer_pool) {
+  if (!pixel_buffer_pool) {
+    LOG(LS_ERROR) << "Failed to get pixel buffer pool.";
+    return nullptr;
+  }
+  CVPixelBufferRef pixel_buffer;
+  CVReturn ret = CVPixelBufferPoolCreatePixelBuffer(nullptr, pixel_buffer_pool,
+                                                    &pixel_buffer);
+  if (ret != kCVReturnSuccess) {
+    LOG(LS_ERROR) << "Failed to create pixel buffer: " << ret;
+    // We probably want to drop frames here, since failure probably means
+    // that the pool is empty.
+    return nullptr;
+  }
+  return pixel_buffer;
+}
+
+// This is the callback function that VideoToolbox calls when encode is
+// complete. From inspection this happens on its own queue.
+void VTCompressionOutputCallback(void* encoder,
+                                 void* params,
+                                 OSStatus status,
+                                 VTEncodeInfoFlags info_flags,
+                                 CMSampleBufferRef sample_buffer) {
+  std::unique_ptr<FrameEncodeParams> encode_params(
+      reinterpret_cast<FrameEncodeParams*>(params));
+  encode_params->encoder->OnEncodedFrame(
+      status, info_flags, sample_buffer, encode_params->codec_specific_info,
+      encode_params->width, encode_params->height,
+      encode_params->render_time_ms, encode_params->timestamp,
+      encode_params->rotation);
+}
+
+// Extract VideoToolbox profile out of the cricket::VideoCodec. If there is no
+// specific VideoToolbox profile for the specified level, AutoLevel will be
+// returned. The user must initialize the encoder with a resolution and
+// framerate conforming to the selected H264 level regardless.
+CFStringRef ExtractProfile(const cricket::VideoCodec& codec) {
+  const rtc::Optional<webrtc::H264::ProfileLevelId> profile_level_id =
+      webrtc::H264::ParseSdpProfileLevelId(codec.params);
+  RTC_DCHECK(profile_level_id);
+  switch (profile_level_id->profile) {
+    case webrtc::H264::kProfileConstrainedBaseline:
+    case webrtc::H264::kProfileBaseline:
+      switch (profile_level_id->level) {
+        case webrtc::H264::kLevel3:
+          return kVTProfileLevel_H264_Baseline_3_0;
+        case webrtc::H264::kLevel3_1:
+          return kVTProfileLevel_H264_Baseline_3_1;
+        case webrtc::H264::kLevel3_2:
+          return kVTProfileLevel_H264_Baseline_3_2;
+        case webrtc::H264::kLevel4:
+          return kVTProfileLevel_H264_Baseline_4_0;
+        case webrtc::H264::kLevel4_1:
+          return kVTProfileLevel_H264_Baseline_4_1;
+        case webrtc::H264::kLevel4_2:
+          return kVTProfileLevel_H264_Baseline_4_2;
+        case webrtc::H264::kLevel5:
+          return kVTProfileLevel_H264_Baseline_5_0;
+        case webrtc::H264::kLevel5_1:
+          return kVTProfileLevel_H264_Baseline_5_1;
+        case webrtc::H264::kLevel5_2:
+          return kVTProfileLevel_H264_Baseline_5_2;
+        case webrtc::H264::kLevel1:
+        case webrtc::H264::kLevel1_b:
+        case webrtc::H264::kLevel1_1:
+        case webrtc::H264::kLevel1_2:
+        case webrtc::H264::kLevel1_3:
+        case webrtc::H264::kLevel2:
+        case webrtc::H264::kLevel2_1:
+        case webrtc::H264::kLevel2_2:
+          return kVTProfileLevel_H264_Baseline_AutoLevel;
+      }
+
+    case webrtc::H264::kProfileMain:
+      switch (profile_level_id->level) {
+        case webrtc::H264::kLevel3:
+          return kVTProfileLevel_H264_Main_3_0;
+        case webrtc::H264::kLevel3_1:
+          return kVTProfileLevel_H264_Main_3_1;
+        case webrtc::H264::kLevel3_2:
+          return kVTProfileLevel_H264_Main_3_2;
+        case webrtc::H264::kLevel4:
+          return kVTProfileLevel_H264_Main_4_0;
+        case webrtc::H264::kLevel4_1:
+          return kVTProfileLevel_H264_Main_4_1;
+        case webrtc::H264::kLevel4_2:
+          return kVTProfileLevel_H264_Main_4_2;
+        case webrtc::H264::kLevel5:
+          return kVTProfileLevel_H264_Main_5_0;
+        case webrtc::H264::kLevel5_1:
+          return kVTProfileLevel_H264_Main_5_1;
+        case webrtc::H264::kLevel5_2:
+          return kVTProfileLevel_H264_Main_5_2;
+        case webrtc::H264::kLevel1:
+        case webrtc::H264::kLevel1_b:
+        case webrtc::H264::kLevel1_1:
+        case webrtc::H264::kLevel1_2:
+        case webrtc::H264::kLevel1_3:
+        case webrtc::H264::kLevel2:
+        case webrtc::H264::kLevel2_1:
+        case webrtc::H264::kLevel2_2:
+          return kVTProfileLevel_H264_Main_AutoLevel;
+      }
+
+    case webrtc::H264::kProfileConstrainedHigh:
+    case webrtc::H264::kProfileHigh:
+      switch (profile_level_id->level) {
+        case webrtc::H264::kLevel3:
+          return kVTProfileLevel_H264_High_3_0;
+        case webrtc::H264::kLevel3_1:
+          return kVTProfileLevel_H264_High_3_1;
+        case webrtc::H264::kLevel3_2:
+          return kVTProfileLevel_H264_High_3_2;
+        case webrtc::H264::kLevel4:
+          return kVTProfileLevel_H264_High_4_0;
+        case webrtc::H264::kLevel4_1:
+          return kVTProfileLevel_H264_High_4_1;
+        case webrtc::H264::kLevel4_2:
+          return kVTProfileLevel_H264_High_4_2;
+        case webrtc::H264::kLevel5:
+          return kVTProfileLevel_H264_High_5_0;
+        case webrtc::H264::kLevel5_1:
+          return kVTProfileLevel_H264_High_5_1;
+        case webrtc::H264::kLevel5_2:
+          return kVTProfileLevel_H264_High_5_2;
+        case webrtc::H264::kLevel1:
+        case webrtc::H264::kLevel1_b:
+        case webrtc::H264::kLevel1_1:
+        case webrtc::H264::kLevel1_2:
+        case webrtc::H264::kLevel1_3:
+        case webrtc::H264::kLevel2:
+        case webrtc::H264::kLevel2_1:
+        case webrtc::H264::kLevel2_2:
+          return kVTProfileLevel_H264_High_AutoLevel;
+      }
+  }
+}
+
+}  // namespace internal
+
+namespace webrtc {
+
+// .5 is set as a mininum to prevent overcompensating for large temporary
+// overshoots. We don't want to degrade video quality too badly.
+// .95 is set to prevent oscillations. When a lower bitrate is set on the
+// encoder than previously set, its output seems to have a brief period of
+// drastically reduced bitrate, so we want to avoid that. In steady state
+// conditions, 0.95 seems to give us better overall bitrate over long periods
+// of time.
+H264VideoToolboxEncoder::H264VideoToolboxEncoder(const cricket::VideoCodec& codec)
+    : callback_(nullptr),
+      compression_session_(nullptr),
+      bitrate_adjuster_(Clock::GetRealTimeClock(), .5, .95),
+      packetization_mode_(H264PacketizationMode::NonInterleaved),
+      profile_(internal::ExtractProfile(codec)) {
+  LOG(LS_INFO) << "Using profile " << internal::CFStringToString(profile_);
+  RTC_CHECK(cricket::CodecNamesEq(codec.name, cricket::kH264CodecName));
+}
+
+H264VideoToolboxEncoder::~H264VideoToolboxEncoder() {
+  DestroyCompressionSession();
+}
+
+int H264VideoToolboxEncoder::InitEncode(const VideoCodec* codec_settings,
+                                        int number_of_cores,
+                                        size_t max_payload_size) {
+  RTC_DCHECK(codec_settings);
+  RTC_DCHECK_EQ(codec_settings->codecType, kVideoCodecH264);
+
+  width_ = codec_settings->width;
+  height_ = codec_settings->height;
+  mode_ = codec_settings->mode;
+  // We can only set average bitrate on the HW encoder.
+  target_bitrate_bps_ = codec_settings->startBitrate;
+  bitrate_adjuster_.SetTargetBitrateBps(target_bitrate_bps_);
+
+  // TODO(tkchin): Try setting payload size via
+  // kVTCompressionPropertyKey_MaxH264SliceBytes.
+
+  return ResetCompressionSession();
+}
+
+int H264VideoToolboxEncoder::Encode(
+    const VideoFrame& frame,
+    const CodecSpecificInfo* codec_specific_info,
+    const std::vector<FrameType>* frame_types) {
+  // |input_frame| size should always match codec settings.
+  RTC_DCHECK_EQ(frame.width(), width_);
+  RTC_DCHECK_EQ(frame.height(), height_);
+  if (!callback_ || !compression_session_) {
+    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
+  }
+#if defined(WEBRTC_IOS)
+  if (!RTCIsUIApplicationActive()) {
+    // Ignore all encode requests when app isn't active. In this state, the
+    // hardware encoder has been invalidated by the OS.
+    return WEBRTC_VIDEO_CODEC_OK;
+  }
+#endif
+  bool is_keyframe_required = false;
+
+  // Get a pixel buffer from the pool and copy frame data over.
+  CVPixelBufferPoolRef pixel_buffer_pool =
+      VTCompressionSessionGetPixelBufferPool(compression_session_);
+#if defined(WEBRTC_IOS)
+  if (!pixel_buffer_pool) {
+    // Kind of a hack. On backgrounding, the compression session seems to get
+    // invalidated, which causes this pool call to fail when the application
+    // is foregrounded and frames are being sent for encoding again.
+    // Resetting the session when this happens fixes the issue.
+    // In addition we request a keyframe so video can recover quickly.
+    ResetCompressionSession();
+    pixel_buffer_pool =
+        VTCompressionSessionGetPixelBufferPool(compression_session_);
+    is_keyframe_required = true;
+    LOG(LS_INFO) << "Resetting compression session due to invalid pool.";
+  }
+#endif
+
+  CVPixelBufferRef pixel_buffer = static_cast<CVPixelBufferRef>(
+      frame.video_frame_buffer()->native_handle());
+  if (pixel_buffer) {
+    // Native frame.
+    rtc::scoped_refptr<CoreVideoFrameBuffer> core_video_frame_buffer(
+        static_cast<CoreVideoFrameBuffer*>(frame.video_frame_buffer().get()));
+    if (!core_video_frame_buffer->RequiresCropping()) {
+      // This pixel buffer might have a higher resolution than what the
+      // compression session is configured to. The compression session can
+      // handle that and will output encoded frames in the configured
+      // resolution regardless of the input pixel buffer resolution.
+      CVBufferRetain(pixel_buffer);
+    } else {
+      // Cropping required, we need to crop and scale to a new pixel buffer.
+      pixel_buffer = internal::CreatePixelBuffer(pixel_buffer_pool);
+      if (!pixel_buffer) {
+        return WEBRTC_VIDEO_CODEC_ERROR;
+      }
+      if (!core_video_frame_buffer->CropAndScaleTo(&nv12_scale_buffer_,
+                                                   pixel_buffer)) {
+        return WEBRTC_VIDEO_CODEC_ERROR;
+      }
+    }
+  } else {
+    pixel_buffer = internal::CreatePixelBuffer(pixel_buffer_pool);
+    if (!pixel_buffer) {
+      return WEBRTC_VIDEO_CODEC_ERROR;
+    }
+    RTC_DCHECK(pixel_buffer);
+    if (!internal::CopyVideoFrameToPixelBuffer(frame.video_frame_buffer(),
+                                               pixel_buffer)) {
+      LOG(LS_ERROR) << "Failed to copy frame data.";
+      CVBufferRelease(pixel_buffer);
+      return WEBRTC_VIDEO_CODEC_ERROR;
+    }
+  }
+
+  // Check if we need a keyframe.
+  if (!is_keyframe_required && frame_types) {
+    for (auto frame_type : *frame_types) {
+      if (frame_type == kVideoFrameKey) {
+        is_keyframe_required = true;
+        break;
+      }
+    }
+  }
+
+  CMTime presentation_time_stamp =
+      CMTimeMake(frame.render_time_ms(), 1000);
+  CFDictionaryRef frame_properties = nullptr;
+  if (is_keyframe_required) {
+    CFTypeRef keys[] = {kVTEncodeFrameOptionKey_ForceKeyFrame};
+    CFTypeRef values[] = {kCFBooleanTrue};
+    frame_properties = internal::CreateCFDictionary(keys, values, 1);
+  }
+  std::unique_ptr<internal::FrameEncodeParams> encode_params;
+  encode_params.reset(new internal::FrameEncodeParams(
+      this, codec_specific_info, width_, height_, frame.render_time_ms(),
+      frame.timestamp(), frame.rotation()));
+
+  encode_params->codec_specific_info.codecSpecific.H264.packetization_mode =
+      packetization_mode_;
+
+  // Update the bitrate if needed.
+  SetBitrateBps(bitrate_adjuster_.GetAdjustedBitrateBps());
+
+  OSStatus status = VTCompressionSessionEncodeFrame(
+      compression_session_, pixel_buffer, presentation_time_stamp,
+      kCMTimeInvalid, frame_properties, encode_params.release(), nullptr);
+  if (frame_properties) {
+    CFRelease(frame_properties);
+  }
+  if (pixel_buffer) {
+    CVBufferRelease(pixel_buffer);
+  }
+  if (status != noErr) {
+    LOG(LS_ERROR) << "Failed to encode frame with code: " << status;
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int H264VideoToolboxEncoder::RegisterEncodeCompleteCallback(
+    EncodedImageCallback* callback) {
+  callback_ = callback;
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int H264VideoToolboxEncoder::SetChannelParameters(uint32_t packet_loss,
+                                                  int64_t rtt) {
+  // Encoder doesn't know anything about packet loss or rtt so just return.
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int H264VideoToolboxEncoder::SetRates(uint32_t new_bitrate_kbit,
+                                      uint32_t frame_rate) {
+  target_bitrate_bps_ = 1000 * new_bitrate_kbit;
+  bitrate_adjuster_.SetTargetBitrateBps(target_bitrate_bps_);
+  SetBitrateBps(bitrate_adjuster_.GetAdjustedBitrateBps());
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int H264VideoToolboxEncoder::Release() {
+  // Need to reset so that the session is invalidated and won't use the
+  // callback anymore. Do not remove callback until the session is invalidated
+  // since async encoder callbacks can occur until invalidation.
+  int ret = ResetCompressionSession();
+  callback_ = nullptr;
+  return ret;
+}
+
+int H264VideoToolboxEncoder::ResetCompressionSession() {
+  DestroyCompressionSession();
+
+  // Set source image buffer attributes. These attributes will be present on
+  // buffers retrieved from the encoder's pixel buffer pool.
+  const size_t attributes_size = 3;
+  CFTypeRef keys[attributes_size] = {
+#if defined(WEBRTC_IOS)
+    kCVPixelBufferOpenGLESCompatibilityKey,
+#elif defined(WEBRTC_MAC)
+    kCVPixelBufferOpenGLCompatibilityKey,
+#endif
+    kCVPixelBufferIOSurfacePropertiesKey,
+    kCVPixelBufferPixelFormatTypeKey
+  };
+  CFDictionaryRef io_surface_value =
+      internal::CreateCFDictionary(nullptr, nullptr, 0);
+  int64_t nv12type = kCVPixelFormatType_420YpCbCr8BiPlanarFullRange;
+  CFNumberRef pixel_format =
+      CFNumberCreate(nullptr, kCFNumberLongType, &nv12type);
+  CFTypeRef values[attributes_size] = {kCFBooleanTrue, io_surface_value,
+                                       pixel_format};
+  CFDictionaryRef source_attributes =
+      internal::CreateCFDictionary(keys, values, attributes_size);
+  if (io_surface_value) {
+    CFRelease(io_surface_value);
+    io_surface_value = nullptr;
+  }
+  if (pixel_format) {
+    CFRelease(pixel_format);
+    pixel_format = nullptr;
+  }
+  OSStatus status = VTCompressionSessionCreate(
+      nullptr,  // use default allocator
+      width_, height_, kCMVideoCodecType_H264,
+      nullptr,  // use default encoder
+      source_attributes,
+      nullptr,  // use default compressed data allocator
+      internal::VTCompressionOutputCallback, this, &compression_session_);
+  if (source_attributes) {
+    CFRelease(source_attributes);
+    source_attributes = nullptr;
+  }
+  if (status != noErr) {
+    LOG(LS_ERROR) << "Failed to create compression session: " << status;
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  ConfigureCompressionSession();
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+void H264VideoToolboxEncoder::ConfigureCompressionSession() {
+  RTC_DCHECK(compression_session_);
+  internal::SetVTSessionProperty(compression_session_,
+                                 kVTCompressionPropertyKey_RealTime, true);
+  internal::SetVTSessionProperty(compression_session_,
+                                 kVTCompressionPropertyKey_ProfileLevel,
+                                 profile_);
+  internal::SetVTSessionProperty(compression_session_,
+                                 kVTCompressionPropertyKey_AllowFrameReordering,
+                                 false);
+  SetEncoderBitrateBps(target_bitrate_bps_);
+  // TODO(tkchin): Look at entropy mode and colorspace matrices.
+  // TODO(tkchin): Investigate to see if there's any way to make this work.
+  // May need it to interop with Android. Currently this call just fails.
+  // On inspecting encoder output on iOS8, this value is set to 6.
+  // internal::SetVTSessionProperty(compression_session_,
+  //     kVTCompressionPropertyKey_MaxFrameDelayCount,
+  //     1);
+
+  // Set a relatively large value for keyframe emission (7200 frames or
+  // 4 minutes).
+  internal::SetVTSessionProperty(
+      compression_session_,
+      kVTCompressionPropertyKey_MaxKeyFrameInterval, 7200);
+  internal::SetVTSessionProperty(
+      compression_session_,
+      kVTCompressionPropertyKey_MaxKeyFrameIntervalDuration, 240);
+}
+
+void H264VideoToolboxEncoder::DestroyCompressionSession() {
+  if (compression_session_) {
+    VTCompressionSessionInvalidate(compression_session_);
+    CFRelease(compression_session_);
+    compression_session_ = nullptr;
+  }
+}
+
+const char* H264VideoToolboxEncoder::ImplementationName() const {
+  return "VideoToolbox";
+}
+
+bool H264VideoToolboxEncoder::SupportsNativeHandle() const {
+  return true;
+}
+
+void H264VideoToolboxEncoder::SetBitrateBps(uint32_t bitrate_bps) {
+  if (encoder_bitrate_bps_ != bitrate_bps) {
+    SetEncoderBitrateBps(bitrate_bps);
+  }
+}
+
+void H264VideoToolboxEncoder::SetEncoderBitrateBps(uint32_t bitrate_bps) {
+  if (compression_session_) {
+    internal::SetVTSessionProperty(compression_session_,
+                                   kVTCompressionPropertyKey_AverageBitRate,
+                                   bitrate_bps);
+
+    // TODO(tkchin): Add a helper method to set array value.
+    int64_t data_limit_bytes_per_second_value = static_cast<int64_t>(
+        bitrate_bps * internal::kLimitToAverageBitRateFactor / 8);
+    CFNumberRef bytes_per_second =
+        CFNumberCreate(kCFAllocatorDefault,
+                       kCFNumberSInt64Type,
+                       &data_limit_bytes_per_second_value);
+    int64_t one_second_value = 1;
+    CFNumberRef one_second =
+        CFNumberCreate(kCFAllocatorDefault,
+                       kCFNumberSInt64Type,
+                       &one_second_value);
+    const void* nums[2] = { bytes_per_second, one_second };
+    CFArrayRef data_rate_limits =
+        CFArrayCreate(nullptr, nums, 2, &kCFTypeArrayCallBacks);
+    OSStatus status =
+        VTSessionSetProperty(compression_session_,
+                             kVTCompressionPropertyKey_DataRateLimits,
+                             data_rate_limits);
+    if (bytes_per_second) {
+      CFRelease(bytes_per_second);
+    }
+    if (one_second) {
+      CFRelease(one_second);
+    }
+    if (data_rate_limits) {
+      CFRelease(data_rate_limits);
+    }
+    if (status != noErr) {
+      LOG(LS_ERROR) << "Failed to set data rate limit";
+    }
+
+    encoder_bitrate_bps_ = bitrate_bps;
+  }
+}
+
+void H264VideoToolboxEncoder::OnEncodedFrame(
+    OSStatus status,
+    VTEncodeInfoFlags info_flags,
+    CMSampleBufferRef sample_buffer,
+    CodecSpecificInfo codec_specific_info,
+    int32_t width,
+    int32_t height,
+    int64_t render_time_ms,
+    uint32_t timestamp,
+    VideoRotation rotation) {
+  if (status != noErr) {
+    LOG(LS_ERROR) << "H264 encode failed.";
+    return;
+  }
+  if (info_flags & kVTEncodeInfo_FrameDropped) {
+    LOG(LS_INFO) << "H264 encode dropped frame.";
+    return;
+  }
+
+  bool is_keyframe = false;
+  CFArrayRef attachments =
+      CMSampleBufferGetSampleAttachmentsArray(sample_buffer, 0);
+  if (attachments != nullptr && CFArrayGetCount(attachments)) {
+    CFDictionaryRef attachment =
+        static_cast<CFDictionaryRef>(CFArrayGetValueAtIndex(attachments, 0));
+    is_keyframe =
+        !CFDictionaryContainsKey(attachment, kCMSampleAttachmentKey_NotSync);
+  }
+
+  if (is_keyframe) {
+    LOG(LS_INFO) << "Generated keyframe";
+  }
+
+  // Convert the sample buffer into a buffer suitable for RTP packetization.
+  // TODO(tkchin): Allocate buffers through a pool.
+  std::unique_ptr<rtc::Buffer> buffer(new rtc::Buffer());
+  std::unique_ptr<webrtc::RTPFragmentationHeader> header;
+  {
+    webrtc::RTPFragmentationHeader* header_raw;
+    bool result = H264CMSampleBufferToAnnexBBuffer(sample_buffer, is_keyframe,
+                                                   buffer.get(), &header_raw);
+    header.reset(header_raw);
+    if (!result) {
+      return;
+    }
+  }
+  webrtc::EncodedImage frame(buffer->data(), buffer->size(), buffer->size());
+  frame._encodedWidth = width;
+  frame._encodedHeight = height;
+  frame._completeFrame = true;
+  frame._frameType =
+      is_keyframe ? webrtc::kVideoFrameKey : webrtc::kVideoFrameDelta;
+  frame.capture_time_ms_ = render_time_ms;
+  frame._timeStamp = timestamp;
+  frame.rotation_ = rotation;
+
+  frame.content_type_ =
+      (mode_ == kScreensharing) ? VideoContentType::SCREENSHARE : VideoContentType::UNSPECIFIED;
+
+  h264_bitstream_parser_.ParseBitstream(buffer->data(), buffer->size());
+  h264_bitstream_parser_.GetLastSliceQp(&frame.qp_);
+
+  EncodedImageCallback::Result res =
+      callback_->OnEncodedImage(frame, &codec_specific_info, header.get());
+  if (res.error != EncodedImageCallback::Result::OK) {
+    LOG(LS_ERROR) << "Encode callback failed: " << res.error;
+    return;
+  }
+  bitrate_adjuster_.Update(frame._length);
+}
+
+VideoEncoder::ScalingSettings H264VideoToolboxEncoder::GetScalingSettings()
+    const {
+  return VideoEncoder::ScalingSettings(true, internal::kLowH264QpThreshold,
+                                       internal::kHighH264QpThreshold);
+}
+}  // namespace webrtc