H264 HW encode using VideoToolbox

media/base/mac/videotoolbox_helpers.cc

Index: media/base/mac/videotoolbox_helpers.cc
diff --git a/media/cast/sender/h264_vt_encoder.cc b/media/base/mac/videotoolbox_helpers.cc
similarity index 20%
copy from media/cast/sender/h264_vt_encoder.cc
copy to media/base/mac/videotoolbox_helpers.cc
index 33e7366d80a3e534653e8b7cfd94c530fac3f28d..a823ced03dcad7646f1f0fec1f38f404588ffe10 100644
--- a/media/cast/sender/h264_vt_encoder.cc
+++ b/media/base/mac/videotoolbox_helpers.cc
@@ -1,47 +1,17 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "media/cast/sender/h264_vt_encoder.h"
+#include "media/base/mac/videotoolbox_helpers.h"
 
-#include <stddef.h>
-
-#include <string>
 #include <vector>
 
 #include "base/big_endian.h"
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/location.h"
-#include "base/logging.h"
-#include "base/macros.h"
-#include "base/power_monitor/power_monitor.h"
-#include "base/synchronization/lock.h"
-#include "build/build_config.h"
-#include "media/base/mac/corevideo_glue.h"
-#include "media/base/mac/video_frame_mac.h"
-#include "media/cast/common/rtp_time.h"
-#include "media/cast/constants.h"
-#include "media/cast/sender/video_frame_factory.h"
+#include "base/memory/scoped_ptr.h"
 
 namespace media {
-namespace cast {
-
-namespace {
-
-// Container for the associated data of a video frame being processed.
-struct InProgressFrameEncode {
-  const RtpTimeTicks rtp_timestamp;
-  const base::TimeTicks reference_time;
-  const VideoEncoder::FrameEncodedCallback frame_encoded_callback;
-
-  InProgressFrameEncode(RtpTimeTicks rtp,
-                        base::TimeTicks r_time,
-                        VideoEncoder::FrameEncodedCallback callback)
-      : rtp_timestamp(rtp),
-        reference_time(r_time),
-        frame_encoded_callback(callback) {}
-};
+
+namespace video_toolbox {
 
 base::ScopedCFTypeRef<CFDictionaryRef>
 DictionaryWithKeysAndValues(CFTypeRef* keys, CFTypeRef* values, size_t size) {
@@ -71,10 +41,64 @@ base::ScopedCFTypeRef<CFArrayRef> ArrayWithIntegers(const int* v, size_t size) {
   return array;
 }
 
+// Wrapper class for writing AnnexBBuffer output into.
+class AnnexBBuffer {
+ public:
+  explicit AnnexBBuffer(std::string* str_annexb_buffer)
+      : type_(STRING_ANNEXB_BUFFER),
+        str_annexb_buffer_(str_annexb_buffer),
+        annexb_buffer_(nullptr) {}
+
+  AnnexBBuffer(uint8_t* annexb_buffer, size_t annexb_buffer_size)
+      : type_(BUFFER_ANNEXB_BUFFER),
+        str_annexb_buffer_(nullptr),
+        annexb_buffer_(annexb_buffer),
+        annexb_buffer_size_(annexb_buffer_size),
+        annexb_buffer_offset_(0) {}
+
+  bool Reserve(size_t size) {
+    reserved_size_ = size;
+    switch (type_) {
+      case STRING_ANNEXB_BUFFER:
+        str_annexb_buffer_->reserve(size);
+        return true;
+      case BUFFER_ANNEXB_BUFFER:
+        return size <= annexb_buffer_size_;
+    }
+  }
+
+  void Append(const char* s, size_t n) {
+    switch (type_) {
+      case STRING_ANNEXB_BUFFER:
+        str_annexb_buffer_->append(s, n);
+        return;
+      case BUFFER_ANNEXB_BUFFER:
+        memcpy(annexb_buffer_ + annexb_buffer_offset_, s, n);
+        annexb_buffer_offset_ += n;
+        DCHECK_GE(reserved_size_, annexb_buffer_offset_);
+        return;
+    }
+  }
+
+  size_t reserved_size() { return reserved_size_; }
+
+ private:
+  enum AnnexBBufferType { STRING_ANNEXB_BUFFER, BUFFER_ANNEXB_BUFFER };
+
+  AnnexBBufferType type_;
+  std::string* str_annexb_buffer_;
+  uint8_t* annexb_buffer_;
+  size_t annexb_buffer_size_;
+  size_t annexb_buffer_offset_;
+  size_t reserved_size_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(AnnexBBuffer);
+};
+
 template <typename NalSizeType>
 void CopyNalsToAnnexB(char* avcc_buffer,
                       const size_t avcc_size,
-                      std::string* annexb_buffer) {
+                      AnnexBBuffer* annexb_buffer) {
   static_assert(sizeof(NalSizeType) == 1 || sizeof(NalSizeType) == 2 ||
                     sizeof(NalSizeType) == 4,
                 "NAL size type has unsupported size");
@@ -90,17 +114,15 @@ void CopyNalsToAnnexB(char* avcc_buffer,
     avcc_buffer += sizeof(NalSizeType);
 
     DCHECK_GE(bytes_left, nal_size);
-    annexb_buffer->append(startcode_3, sizeof(startcode_3));
-    annexb_buffer->append(avcc_buffer, nal_size);
+    annexb_buffer->Append(startcode_3, sizeof(startcode_3));
+    annexb_buffer->Append(avcc_buffer, nal_size);
     bytes_left -= nal_size;
     avcc_buffer += nal_size;
   }
 }
 
-// Copy a H.264 frame stored in a CM sample buffer to an Annex B buffer. Copies
-// parameter sets for keyframes before the frame data as well.
-void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
-                                    std::string* annexb_buffer,
+bool CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
+                                    AnnexBBuffer* annexb_buffer,
                                     bool keyframe) {
   // Perform two pass, one to figure out the total output size, and another to
   // copy the data after having performed a single output allocation. Note that
@@ -131,7 +153,7 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
     DLOG(ERROR)
         << " CMVideoFormatDescriptionGetH264ParameterSetAtIndex failed: "
         << status;
-    return;
+    return false;
   }
 
   if (keyframe) {
@@ -145,13 +167,16 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
         DLOG(ERROR)
             << " CMVideoFormatDescriptionGetH264ParameterSetAtIndex failed: "
             << status;
-        return;
+        return false;
       }
       total_bytes += pset_size + nal_size_field_bytes;
     }
   }
 
-  annexb_buffer->reserve(total_bytes);
+  if (!annexb_buffer->Reserve(total_bytes)) {
+    DLOG(ERROR) << "Cannot fit encode output into bitstream buffer.";
+    return false;
+  }
 
   // Copy all parameter sets before keyframes.
   if (keyframe) {
@@ -165,11 +190,11 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
         DLOG(ERROR)
             << " CMVideoFormatDescriptionGetH264ParameterSetAtIndex failed: "
             << status;
-        return;
+        return false;
       }
       static const char startcode_4[4] = {0, 0, 0, 1};
-      annexb_buffer->append(startcode_4, sizeof(startcode_4));
-      annexb_buffer->append(reinterpret_cast<const char*>(pset), pset_size);
+      annexb_buffer->Append(startcode_4, sizeof(startcode_4));
+      annexb_buffer->Append(reinterpret_cast<const char*>(pset), pset_size);
     }
   }
 
@@ -184,7 +209,7 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
         contiguous_bb.InitializeInto());
     if (status != noErr) {
       DLOG(ERROR) << " CMBlockBufferCreateContiguous failed: " << status;
-      return;
+      return false;
     }
   }
 
@@ -195,7 +220,7 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
                                                       nullptr, &bb_data);
   if (status != noErr) {
     DLOG(ERROR) << " CMBlockBufferGetDataPointer failed: " << status;
-    return;
+    return false;
   }
 
   if (nal_size_field_bytes == 1) {
@@ -207,563 +232,52 @@ void CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
   } else {
     NOTREACHED();
   }
-}
-
-}  // namespace
-
-class H264VideoToolboxEncoder::VideoFrameFactoryImpl
-    : public base::RefCountedThreadSafe<VideoFrameFactoryImpl>,
-      public VideoFrameFactory {
- public:
-  // Type that proxies the VideoFrameFactory interface to this class.
-  class Proxy;
-
-  VideoFrameFactoryImpl(const base::WeakPtr<H264VideoToolboxEncoder>& encoder,
-                        const scoped_refptr<CastEnvironment>& cast_environment)
-      : encoder_(encoder), cast_environment_(cast_environment) {}
-
-  scoped_refptr<VideoFrame> MaybeCreateFrame(
-      const gfx::Size& frame_size,
-      base::TimeDelta timestamp) final {
-    if (frame_size.IsEmpty()) {
-      DVLOG(1) << "Rejecting empty video frame.";
-      return nullptr;
-    }
-
-    base::AutoLock auto_lock(lock_);
-
-    // If the pool size does not match, speculatively reset the encoder to use
-    // the new size and return null. Cache the new frame size right away and
-    // toss away the pixel buffer pool to avoid spurious tasks until the encoder
-    // is done resetting.
-    if (frame_size != pool_frame_size_) {
-      DVLOG(1) << "MaybeCreateFrame: Detected frame size change.";
-      cast_environment_->PostTask(
-          CastEnvironment::MAIN, FROM_HERE,
-          base::Bind(&H264VideoToolboxEncoder::UpdateFrameSize, encoder_,
-                     frame_size));
-      pool_frame_size_ = frame_size;
-      pool_.reset();
-      return nullptr;
-    }
-
-    if (!pool_) {
-      DVLOG(1) << "MaybeCreateFrame: No pixel buffer pool.";
-      return nullptr;
-    }
-
-    // Allocate a pixel buffer from the pool and return a wrapper VideoFrame.
-    base::ScopedCFTypeRef<CVPixelBufferRef> buffer;
-    auto status = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pool_,
-                                                     buffer.InitializeInto());
-    if (status != kCVReturnSuccess) {
-      DLOG(ERROR) << "CVPixelBufferPoolCreatePixelBuffer failed: " << status;
-      return nullptr;
-    }
-
-    DCHECK(buffer);
-    return VideoFrame::WrapCVPixelBuffer(buffer, timestamp);
-  }
-
-  void Update(const base::ScopedCFTypeRef<CVPixelBufferPoolRef>& pool,
-              const gfx::Size& frame_size) {
-    base::AutoLock auto_lock(lock_);
-    pool_ = pool;
-    pool_frame_size_ = frame_size;
-  }
-
- private:
-  friend class base::RefCountedThreadSafe<VideoFrameFactoryImpl>;
-  ~VideoFrameFactoryImpl() final {}
-
-  base::Lock lock_;
-  base::ScopedCFTypeRef<CVPixelBufferPoolRef> pool_;
-  gfx::Size pool_frame_size_;
-
-  // Weak back reference to the encoder and the cast envrionment so we can
-  // message the encoder when the frame size changes.
-  const base::WeakPtr<H264VideoToolboxEncoder> encoder_;
-  const scoped_refptr<CastEnvironment> cast_environment_;
-
-  DISALLOW_COPY_AND_ASSIGN(VideoFrameFactoryImpl);
-};
-
-class H264VideoToolboxEncoder::VideoFrameFactoryImpl::Proxy
-    : public VideoFrameFactory {
- public:
-  explicit Proxy(
-      const scoped_refptr<VideoFrameFactoryImpl>& video_frame_factory)
-      : video_frame_factory_(video_frame_factory) {
-    DCHECK(video_frame_factory_);
-  }
-
-  scoped_refptr<VideoFrame> MaybeCreateFrame(
-      const gfx::Size& frame_size,
-      base::TimeDelta timestamp) final {
-    return video_frame_factory_->MaybeCreateFrame(frame_size, timestamp);
-  }
-
- private:
-  ~Proxy() final {}
-
-  const scoped_refptr<VideoFrameFactoryImpl> video_frame_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(Proxy);
-};
-
-// static
-bool H264VideoToolboxEncoder::IsSupported(
-    const VideoSenderConfig& video_config) {
-  return video_config.codec == CODEC_VIDEO_H264 && VideoToolboxGlue::Get();
-}
-
-H264VideoToolboxEncoder::H264VideoToolboxEncoder(
-    const scoped_refptr<CastEnvironment>& cast_environment,
-    const VideoSenderConfig& video_config,
-    const StatusChangeCallback& status_change_cb)
-    : cast_environment_(cast_environment),
-      videotoolbox_glue_(VideoToolboxGlue::Get()),
-      video_config_(video_config),
-      status_change_cb_(status_change_cb),
-      last_frame_id_(kFirstFrameId - 1),
-      encode_next_frame_as_keyframe_(false),
-      power_suspended_(false),
-      weak_factory_(this) {
-  DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::MAIN));
-  DCHECK(!status_change_cb_.is_null());
-
-  OperationalStatus operational_status =
-      H264VideoToolboxEncoder::IsSupported(video_config)
-          ? STATUS_INITIALIZED
-          : STATUS_UNSUPPORTED_CODEC;
-  cast_environment_->PostTask(
-      CastEnvironment::MAIN, FROM_HERE,
-      base::Bind(status_change_cb_, operational_status));
-
-  if (operational_status == STATUS_INITIALIZED) {
-    // Create the shared video frame factory. It persists for the combined
-    // lifetime of the encoder and all video frame factory proxies created by
-    // |CreateVideoFrameFactory| that reference it.
-    video_frame_factory_ =
-        scoped_refptr<VideoFrameFactoryImpl>(new VideoFrameFactoryImpl(
-            weak_factory_.GetWeakPtr(), cast_environment_));
-
-    // Register for power state changes.
-    auto power_monitor = base::PowerMonitor::Get();
-    if (power_monitor) {
-      power_monitor->AddObserver(this);
-      VLOG(1) << "Registered for power state changes.";
-    } else {
-      DLOG(WARNING) << "No power monitor. Process suspension will invalidate "
-                       "the encoder.";
-    }
-  }
-}
-
-H264VideoToolboxEncoder::~H264VideoToolboxEncoder() {
-  DestroyCompressionSession();
-
-  // If video_frame_factory_ is not null, the encoder registered for power state
-  // changes in the ctor and it must now unregister.
-  if (video_frame_factory_) {
-    auto power_monitor = base::PowerMonitor::Get();
-    if (power_monitor)
-      power_monitor->RemoveObserver(this);
-  }
-}
-
-void H264VideoToolboxEncoder::ResetCompressionSession() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // Ignore reset requests while power suspended.
-  if (power_suspended_)
-    return;
-
-  // Notify that we're resetting the encoder.
-  cast_environment_->PostTask(
-      CastEnvironment::MAIN, FROM_HERE,
-      base::Bind(status_change_cb_, STATUS_CODEC_REINIT_PENDING));
-
-  // Destroy the current session, if any.
-  DestroyCompressionSession();
-
-  // On OS X, allow the hardware encoder. Don't require it, it does not support
-  // all configurations (some of which are used for testing).
-  base::ScopedCFTypeRef<CFDictionaryRef> encoder_spec;
-#if !defined(OS_IOS)
-  encoder_spec = DictionaryWithKeyValue(
-      videotoolbox_glue_
-          ->kVTVideoEncoderSpecification_EnableHardwareAcceleratedVideoEncoder(),
-      kCFBooleanTrue);
-#endif
-
-  // Force 420v so that clients can easily use these buffers as GPU textures.
-  const int format[] = {
-      CoreVideoGlue::kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange};
-
-  // Keep these attachment settings in-sync with those in ConfigureSession().
-  CFTypeRef attachments_keys[] = {kCVImageBufferColorPrimariesKey,
-                                  kCVImageBufferTransferFunctionKey,
-                                  kCVImageBufferYCbCrMatrixKey};
-  CFTypeRef attachments_values[] = {kCVImageBufferColorPrimaries_ITU_R_709_2,
-                                    kCVImageBufferTransferFunction_ITU_R_709_2,
-                                    kCVImageBufferYCbCrMatrix_ITU_R_709_2};
-  CFTypeRef buffer_attributes_keys[] = {kCVPixelBufferPixelFormatTypeKey,
-                                        kCVBufferPropagatedAttachmentsKey};
-  CFTypeRef buffer_attributes_values[] = {
-      ArrayWithIntegers(format, arraysize(format)).release(),
-      DictionaryWithKeysAndValues(attachments_keys, attachments_values,
-                                  arraysize(attachments_keys)).release()};
-  const base::ScopedCFTypeRef<CFDictionaryRef> buffer_attributes =
-      DictionaryWithKeysAndValues(buffer_attributes_keys,
-                                  buffer_attributes_values,
-                                  arraysize(buffer_attributes_keys));
-  for (auto& v : buffer_attributes_values)
-    CFRelease(v);
-
-  // Create the compression session.
-
-  // Note that the encoder object is given to the compression session as the
-  // callback context using a raw pointer. The C API does not allow us to use a
-  // smart pointer, nor is this encoder ref counted. However, this is still
-  // safe, because we 1) we own the compression session and 2) we tear it down
-  // safely. When destructing the encoder, the compression session is flushed
-  // and invalidated. Internally, VideoToolbox will join all of its threads
-  // before returning to the client. Therefore, when control returns to us, we
-  // are guaranteed that the output callback will not execute again.
-  OSStatus status = videotoolbox_glue_->VTCompressionSessionCreate(
-      kCFAllocatorDefault, frame_size_.width(), frame_size_.height(),
-      CoreMediaGlue::kCMVideoCodecType_H264, encoder_spec, buffer_attributes,
-      nullptr /* compressedDataAllocator */,
-      &H264VideoToolboxEncoder::CompressionCallback,
-      reinterpret_cast<void*>(this), compression_session_.InitializeInto());
-  if (status != noErr) {
-    DLOG(ERROR) << " VTCompressionSessionCreate failed: " << status;
-    // Notify that reinitialization has failed.
-    cast_environment_->PostTask(
-        CastEnvironment::MAIN, FROM_HERE,
-        base::Bind(status_change_cb_, STATUS_CODEC_INIT_FAILED));
-    return;
-  }
-
-  // Configure the session (apply session properties based on the current state
-  // of the encoder, experimental tuning and requirements).
-  ConfigureCompressionSession();
-
-  // Update the video frame factory.
-  base::ScopedCFTypeRef<CVPixelBufferPoolRef> pool(
-      videotoolbox_glue_->VTCompressionSessionGetPixelBufferPool(
-          compression_session_),
-      base::scoped_policy::RETAIN);
-  video_frame_factory_->Update(pool, frame_size_);
-
-  // Notify that reinitialization is done.
-  cast_environment_->PostTask(
-      CastEnvironment::MAIN, FROM_HERE,
-      base::Bind(status_change_cb_, STATUS_INITIALIZED));
-}
-
-void H264VideoToolboxEncoder::ConfigureCompressionSession() {
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_ProfileLevel(),
-      videotoolbox_glue_->kVTProfileLevel_H264_Main_AutoLevel());
-  SetSessionProperty(videotoolbox_glue_->kVTCompressionPropertyKey_RealTime(),
-                     true);
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_AllowFrameReordering(),
-      false);
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_MaxKeyFrameInterval(), 240);
-  SetSessionProperty(
-      videotoolbox_glue_
-          ->kVTCompressionPropertyKey_MaxKeyFrameIntervalDuration(),
-      240);
-  // TODO(jfroy): implement better bitrate control
-  //              https://crbug.com/425352
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_AverageBitRate(),
-      (video_config_.min_bitrate + video_config_.max_bitrate) / 2);
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_ExpectedFrameRate(),
-      video_config_.max_frame_rate);
-  // Keep these attachment settings in-sync with those in Initialize().
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_ColorPrimaries(),
-      kCVImageBufferColorPrimaries_ITU_R_709_2);
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_TransferFunction(),
-      kCVImageBufferTransferFunction_ITU_R_709_2);
-  SetSessionProperty(
-      videotoolbox_glue_->kVTCompressionPropertyKey_YCbCrMatrix(),
-      kCVImageBufferYCbCrMatrix_ITU_R_709_2);
-  if (video_config_.max_number_of_video_buffers_used > 0) {
-    SetSessionProperty(
-        videotoolbox_glue_->kVTCompressionPropertyKey_MaxFrameDelayCount(),
-        video_config_.max_number_of_video_buffers_used);
-  }
-}
-
-void H264VideoToolboxEncoder::DestroyCompressionSession() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // If the compression session exists, invalidate it. This blocks until all
-  // pending output callbacks have returned and any internal threads have
-  // joined, ensuring no output callback ever sees a dangling encoder pointer.
-  //
-  // Before destroying the compression session, the video frame factory's pool
-  // is updated to null so that no thread will produce new video frames via the
-  // factory until a new compression session is created. The current frame size
-  // is passed to prevent the video frame factory from posting |UpdateFrameSize|
-  // tasks. Indeed, |DestroyCompressionSession| is either called from
-  // |ResetCompressionSession|, in which case a new pool and frame size will be
-  // set, or from callsites that require that there be no compression session
-  // (ex: the dtor).
-  if (compression_session_) {
-    video_frame_factory_->Update(
-        base::ScopedCFTypeRef<CVPixelBufferPoolRef>(nullptr), frame_size_);
-    videotoolbox_glue_->VTCompressionSessionInvalidate(compression_session_);
-    compression_session_.reset();
-  }
-}
-
-bool H264VideoToolboxEncoder::EncodeVideoFrame(
-    const scoped_refptr<media::VideoFrame>& video_frame,
-    const base::TimeTicks& reference_time,
-    const FrameEncodedCallback& frame_encoded_callback) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!frame_encoded_callback.is_null());
-
-  // Reject empty video frames.
-  const gfx::Size frame_size = video_frame->visible_rect().size();
-  if (frame_size.IsEmpty()) {
-    DVLOG(1) << "Rejecting empty video frame.";
-    return false;
-  }
-
-  // Handle frame size changes. This will reset the compression session.
-  if (frame_size != frame_size_) {
-    DVLOG(1) << "EncodeVideoFrame: Detected frame size change.";
-    UpdateFrameSize(frame_size);
-  }
-
-  // Need a compression session to continue.
-  if (!compression_session_) {
-    DLOG(ERROR) << "No compression session.";
-    return false;
-  }
-
-  // Wrap the VideoFrame in a CVPixelBuffer. In all cases, no data will be
-  // copied. If the VideoFrame was created by this encoder's video frame
-  // factory, then the returned CVPixelBuffer will have been obtained from the
-  // compression session's pixel buffer pool. This will eliminate a copy of the
-  // frame into memory visible by the hardware encoder. The VideoFrame's
-  // lifetime is extended for the lifetime of the returned CVPixelBuffer.
-  auto pixel_buffer = media::WrapVideoFrameInCVPixelBuffer(*video_frame);
-  if (!pixel_buffer) {
-    DLOG(ERROR) << "WrapVideoFrameInCVPixelBuffer failed.";
-    return false;
-  }
-
-  // Convert the frame timestamp to CMTime.
-  auto timestamp_cm = CoreMediaGlue::CMTimeMake(
-      (reference_time - base::TimeTicks()).InMicroseconds(), USEC_PER_SEC);
-
-  // Wrap information we'll need after the frame is encoded in a heap object.
-  // We'll get the pointer back from the VideoToolbox completion callback.
-  scoped_ptr<InProgressFrameEncode> request(new InProgressFrameEncode(
-      RtpTimeTicks::FromTimeDelta(video_frame->timestamp(), kVideoFrequency),
-      reference_time, frame_encoded_callback));
-
-  // Build a suitable frame properties dictionary for keyframes.
-  base::ScopedCFTypeRef<CFDictionaryRef> frame_props;
-  if (encode_next_frame_as_keyframe_) {
-    frame_props = DictionaryWithKeyValue(
-        videotoolbox_glue_->kVTEncodeFrameOptionKey_ForceKeyFrame(),
-        kCFBooleanTrue);
-    encode_next_frame_as_keyframe_ = false;
-  }
-
-  // Submit the frame to the compression session. The function returns as soon
-  // as the frame has been enqueued.
-  OSStatus status = videotoolbox_glue_->VTCompressionSessionEncodeFrame(
-      compression_session_, pixel_buffer, timestamp_cm,
-      CoreMediaGlue::CMTime{0, 0, 0, 0}, frame_props,
-      reinterpret_cast<void*>(request.release()), nullptr);
-  if (status != noErr) {
-    DLOG(ERROR) << " VTCompressionSessionEncodeFrame failed: " << status;
-    return false;
-  }
-
   return true;
 }
 
-void H264VideoToolboxEncoder::UpdateFrameSize(const gfx::Size& size_needed) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // Our video frame factory posts a task to update the frame size when its
-  // cache of the frame size differs from what the client requested. To avoid
-  // spurious encoder resets, check again here.
-  if (size_needed == frame_size_) {
-    DCHECK(compression_session_);
-    return;
-  }
-
-  VLOG(1) << "Resetting compression session (for frame size change from "
-          << frame_size_.ToString() << " to " << size_needed.ToString() << ").";
-
-  // If there is an existing session, finish every pending frame.
-  if (compression_session_) {
-    EmitFrames();
-  }
-
-  // Store the new frame size.
-  frame_size_ = size_needed;
-
-  // Reset the compression session.
-  ResetCompressionSession();
-}
-
-void H264VideoToolboxEncoder::SetBitRate(int /*new_bit_rate*/) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  // VideoToolbox does not seem to support bitrate reconfiguration.
-}
-
-void H264VideoToolboxEncoder::GenerateKeyFrame() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  encode_next_frame_as_keyframe_ = true;
-}
-
-scoped_ptr<VideoFrameFactory>
-H264VideoToolboxEncoder::CreateVideoFrameFactory() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  return scoped_ptr<VideoFrameFactory>(
-      new VideoFrameFactoryImpl::Proxy(video_frame_factory_));
-}
-
-void H264VideoToolboxEncoder::EmitFrames() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  if (!compression_session_)
-    return;
-
-  OSStatus status = videotoolbox_glue_->VTCompressionSessionCompleteFrames(
-      compression_session_, CoreMediaGlue::CMTime{0, 0, 0, 0});
-  if (status != noErr) {
-    DLOG(ERROR) << " VTCompressionSessionCompleteFrames failed: " << status;
-  }
+bool CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
+                                    std::string* annexb_buffer,
+                                    bool keyframe) {
+  scoped_ptr<AnnexBBuffer> buffer(new AnnexBBuffer(annexb_buffer));
+  return CopySampleBufferToAnnexBBuffer(sbuf, buffer.get(), keyframe);
 }
 
-void H264VideoToolboxEncoder::OnSuspend() {
-  VLOG(1)
-      << "OnSuspend: Emitting all frames and destroying compression session.";
-  EmitFrames();
-  DestroyCompressionSession();
-  power_suspended_ = true;
+bool CopySampleBufferToAnnexBBuffer(CoreMediaGlue::CMSampleBufferRef sbuf,
+                                    uint8_t* annexb_buffer,
+                                    size_t annexb_buffer_size,
+                                    bool keyframe,
+                                    size_t* used_buffer_size) {
+  scoped_ptr<AnnexBBuffer> buffer(
+      new AnnexBBuffer(annexb_buffer, annexb_buffer_size));
+  const bool copy_rv =
+      CopySampleBufferToAnnexBBuffer(sbuf, buffer.get(), keyframe);
+  *used_buffer_size = buffer->reserved_size();
+  return copy_rv;
 }
 
-void H264VideoToolboxEncoder::OnResume() {
-  power_suspended_ = false;
+SessionPropertySetter::SessionPropertySetter(
+    base::ScopedCFTypeRef<VideoToolboxGlue::VTCompressionSessionRef> session,
+    const VideoToolboxGlue* const glue)
+    : session_(session), glue_(glue) {}
 
-  // Reset the compression session only if the frame size is not zero (which
-  // will obviously fail). It is possible for the frame size to be zero if no
-  // frame was submitted for encoding or requested from the video frame factory
-  // before suspension.
-  if (!frame_size_.IsEmpty()) {
-    VLOG(1) << "OnResume: Resetting compression session.";
-    ResetCompressionSession();
-  }
-}
+SessionPropertySetter::~SessionPropertySetter() {}
 
-bool H264VideoToolboxEncoder::SetSessionProperty(CFStringRef key,
-                                                 int32_t value) {
+bool SessionPropertySetter::SetSessionProperty(CFStringRef key, int32_t value) {
   base::ScopedCFTypeRef<CFNumberRef> cfvalue(
       CFNumberCreate(nullptr, kCFNumberSInt32Type, &value));
-  return videotoolbox_glue_->VTSessionSetProperty(compression_session_, key,
-                                                  cfvalue) == noErr;
+  return glue_->VTSessionSetProperty(session_, key, cfvalue) == noErr;
 }
 
-bool H264VideoToolboxEncoder::SetSessionProperty(CFStringRef key, bool value) {
+bool SessionPropertySetter::SetSessionProperty(CFStringRef key, bool value) {
   CFBooleanRef cfvalue = (value) ? kCFBooleanTrue : kCFBooleanFalse;
-  return videotoolbox_glue_->VTSessionSetProperty(compression_session_, key,
-                                                  cfvalue) == noErr;
+  return glue_->VTSessionSetProperty(session_, key, cfvalue) == noErr;
 }
 
-bool H264VideoToolboxEncoder::SetSessionProperty(CFStringRef key,
-                                                 CFStringRef value) {
-  return videotoolbox_glue_->VTSessionSetProperty(compression_session_, key,
-                                                  value) == noErr;
+bool SessionPropertySetter::SetSessionProperty(CFStringRef key,
+                                               CFStringRef value) {
+  return glue_->VTSessionSetProperty(session_, key, value) == noErr;
 }
 
-void H264VideoToolboxEncoder::CompressionCallback(void* encoder_opaque,
-                                                  void* request_opaque,
-                                                  OSStatus status,
-                                                  VTEncodeInfoFlags info,
-                                                  CMSampleBufferRef sbuf) {
-  auto encoder = reinterpret_cast<H264VideoToolboxEncoder*>(encoder_opaque);
-  const scoped_ptr<InProgressFrameEncode> request(
-      reinterpret_cast<InProgressFrameEncode*>(request_opaque));
-  bool keyframe = false;
-  bool has_frame_data = false;
-
-  if (status != noErr) {
-    DLOG(ERROR) << " encoding failed: " << status;
-    encoder->cast_environment_->PostTask(
-        CastEnvironment::MAIN, FROM_HERE,
-        base::Bind(encoder->status_change_cb_, STATUS_CODEC_RUNTIME_ERROR));
-  } else if ((info & VideoToolboxGlue::kVTEncodeInfo_FrameDropped)) {
-    DVLOG(2) << " frame dropped";
-  } else {
-    auto sample_attachments =
-        static_cast<CFDictionaryRef>(CFArrayGetValueAtIndex(
-            CoreMediaGlue::CMSampleBufferGetSampleAttachmentsArray(sbuf, true),
-            0));
-
-    // If the NotSync key is not present, it implies Sync, which indicates a
-    // keyframe (at least I think, VT documentation is, erm, sparse). Could
-    // alternatively use kCMSampleAttachmentKey_DependsOnOthers == false.
-    keyframe = !CFDictionaryContainsKey(
-                   sample_attachments,
-                   CoreMediaGlue::kCMSampleAttachmentKey_NotSync());
-    has_frame_data = true;
-  }
-
-  // Increment the encoder-scoped frame id and assign the new value to this
-  // frame. VideoToolbox calls the output callback serially, so this is safe.
-  const uint32_t frame_id = ++encoder->last_frame_id_;
-
-  scoped_ptr<SenderEncodedFrame> encoded_frame(new SenderEncodedFrame());
-  encoded_frame->frame_id = frame_id;
-  encoded_frame->reference_time = request->reference_time;
-  encoded_frame->rtp_timestamp = request->rtp_timestamp;
-  if (keyframe) {
-    encoded_frame->dependency = EncodedFrame::KEY;
-    encoded_frame->referenced_frame_id = frame_id;
-  } else {
-    encoded_frame->dependency = EncodedFrame::DEPENDENT;
-    // H.264 supports complex frame reference schemes (multiple reference
-    // frames, slice references, backward and forward references, etc). Cast
-    // doesn't support the concept of forward-referencing frame dependencies or
-    // multiple frame dependencies; so pretend that all frames are only
-    // decodable after their immediately preceding frame is decoded. This will
-    // ensure a Cast receiver only attempts to decode the frames sequentially
-    // and in order. Furthermore, the encoder is configured to never use forward
-    // references (see |kVTCompressionPropertyKey_AllowFrameReordering|). There
-    // is no way to prevent multiple reference frames.
-    encoded_frame->referenced_frame_id = frame_id - 1;
-  }
-
-  if (has_frame_data)
-    CopySampleBufferToAnnexBBuffer(sbuf, &encoded_frame->data, keyframe);
-
-  // TODO(miu): Compute and populate the |deadline_utilization| and
-  // |lossy_utilization| performance metrics in |encoded_frame|.
-
-  encoded_frame->encode_completion_time =
-      encoder->cast_environment_->Clock()->NowTicks();
-  encoder->cast_environment_->PostTask(
-      CastEnvironment::MAIN, FROM_HERE,
-      base::Bind(request->frame_encoded_callback,
-                 base::Passed(&encoded_frame)));
-}
+}  // namespace video_toolbox
 
-}  // namespace cast
 }  // namespace media