Integrate VDA with WebRTC.

content/renderer/media/rtc_video_decoder.cc

Index: content/renderer/media/rtc_video_decoder.cc
diff --git a/content/renderer/media/rtc_video_decoder.cc b/content/renderer/media/rtc_video_decoder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9af61690dc11ec7d9526ada78eb50d7b2c139f83
--- /dev/null
+++ b/content/renderer/media/rtc_video_decoder.cc
@@ -0,0 +1,736 @@
+// Copyright (c) 2013 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 "content/renderer/media/rtc_video_decoder.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/safe_numerics.h"
+#include "base/stl_util.h"
+#include "base/task_runner_util.h"
+#include "content/child/child_thread.h"
+#include "media/base/bind_to_loop.h"
+#include "third_party/webrtc/system_wrappers/interface/ref_count.h"
+
+namespace content {
+
+const int32 RTCVideoDecoder::ID_LAST = 0x3FFFFFFF;
+const int32 RTCVideoDecoder::ID_HALF = 0x20000000;
+const int32 RTCVideoDecoder::ID_INVALID = -1;
+
+// Maximum number of concurrent VDA::Decode() operations RVD will maintain.
+// Higher values allow better pipelining in the GPU, but also require more
+// resources.
+static const size_t kMaxInFlightDecodes = 8;
+
+// Size of shared-memory segments we allocate.  Since we reuse them we let them
+// be on the beefy side.
+static const size_t kSharedMemorySegmentBytes = 100 << 10;
+
+// Maximum number of allocated shared-memory segments.
+static const int kMaxNumSharedMemorySegments = 16;
+
+// Maximum number of pending WebRTC buffers that are waiting for the shared
+// memory. 10 seconds for 30 fps.
+static const size_t kMaxNumOfPendingBuffers = 300;
+
+// A shared memory segment and its allocated size. This class has the ownership
+// of |shm|.
+class RTCVideoDecoder::SHMBuffer {
+ public:
+  SHMBuffer(base::SharedMemory* shm, size_t size);
+  ~SHMBuffer();
+  base::SharedMemory* const shm;
+  const size_t size;
+};
+
+RTCVideoDecoder::SHMBuffer::SHMBuffer(base::SharedMemory* shm, size_t size)
+    : shm(shm), size(size) {}
+
+RTCVideoDecoder::SHMBuffer::~SHMBuffer() { shm->Close(); }
+
+RTCVideoDecoder::BufferData::BufferData(int32 bitstream_buffer_id,
+                                        uint32_t timestamp,
+                                        int width,
+                                        int height,
+                                        size_t size)
+    : bitstream_buffer_id(bitstream_buffer_id),
+      timestamp(timestamp),
+      width(width),
+      height(height),
+      size(size) {}
+
+RTCVideoDecoder::BufferData::BufferData() {}
+
+RTCVideoDecoder::BufferData::~BufferData() {}
+
+RTCVideoDecoder::RTCVideoDecoder(
+    const scoped_refptr<media::GpuVideoDecoder::Factories>& factories)
+    : weak_factory_(this),
+      weak_this_(weak_factory_.GetWeakPtr()),
+      factories_(factories),
+      vda_loop_proxy_(factories_->GetMessageLoop()),
+      create_shm_thread_("CreateSHMThread"),
+      decoder_texture_target_(0),
+      next_picture_buffer_id_(0),
+      state_(UNINITIALIZED),
+      decode_complete_callback_(NULL),
+      num_shm_buffers_(0),
+      next_bitstream_buffer_id_(0),
+      reset_bitstream_buffer_id_(ID_INVALID) {
+  create_shm_thread_.Start();
+  // Initialize directly if |vda_loop_proxy_| is the renderer thread.
+  base::WaitableEvent compositor_loop_async_waiter(false, false);
+  if (vda_loop_proxy_->BelongsToCurrentThread()) {
+    Initialize(&compositor_loop_async_waiter);
+    return;
+  }
+  // Post the task if |vda_loop_proxy_| is the compositor thread. Waiting here
+  // is safe because the compositor thread will not be stopped until the
+  // renderer thread shuts down.
+  vda_loop_proxy_->PostTask(FROM_HERE,
+                            base::Bind(&RTCVideoDecoder::Initialize,
+                                       base::Unretained(this),
+                                       &compositor_loop_async_waiter));
+  compositor_loop_async_waiter.Wait();
+}
+
+RTCVideoDecoder::~RTCVideoDecoder() {
+  DVLOG(2) << "~RTCVideoDecoder";
+  factories_->Abort();
+  create_shm_thread_.Stop();
+  // Delete vda and remove |this| from the observer if vda thread is alive.
+  if (vda_loop_proxy_->BelongsToCurrentThread()) {
+    base::MessageLoop::current()->RemoveDestructionObserver(this);
+    DestroyVDA();
+  } else {
+    // VDA should have been destroyed in WillDestroyCurrentMessageLoop.
+    DCHECK(!vda_);
+  }
+
+  // Delete all shared memories.
+  STLDeleteElements(&available_shm_segments_);
+  STLDeleteValues(&bitstream_buffers_in_decoder_);
+  STLDeleteContainerPairFirstPointers(decode_buffers_.begin(),
+                                      decode_buffers_.end());
+  decode_buffers_.clear();
+
+  // Delete WebRTC input buffers.
+  for (std::deque<std::pair<webrtc::EncodedImage, BufferData> >::iterator it =
+           pending_buffers_.begin();
+       it != pending_buffers_.end();
+       ++it) {
+    delete[] it->first._buffer;
+  }
+}
+
+scoped_ptr<RTCVideoDecoder> RTCVideoDecoder::Create(
+    const scoped_refptr<media::GpuVideoDecoder::Factories>& factories) {
+  scoped_ptr<RTCVideoDecoder> decoder(new RTCVideoDecoder(factories));
+  decoder->vda_.reset(factories->CreateVideoDecodeAccelerator(
+      media::VP8PROFILE_MAIN, decoder.get()));
+  // vda can be NULL if VP8 is not supported.
+  if (decoder->vda_ != NULL) {
+    decoder->state_ = INITIALIZED;
+  } else {
+    factories->GetMessageLoop()->DeleteSoon(FROM_HERE, decoder.release());
+  }
+  return decoder.Pass();
+}
+
+int32_t RTCVideoDecoder::InitDecode(const webrtc::VideoCodec* codecSettings,
+                                    int32_t /*numberOfCores*/) {
+  DVLOG(2) << "InitDecode";
+  DCHECK_EQ(codecSettings->codecType, webrtc::kVideoCodecVP8);
+  if (codecSettings->codecSpecific.VP8.feedbackModeOn) {
+    LOG(ERROR) << "Feedback mode not supported";
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+
+  base::AutoLock auto_lock(lock_);
+  if (state_ == UNINITIALIZED || state_ == DECODE_ERROR) {
+    LOG(ERROR) << "VDA is not initialized. state=" << state_;
+    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
+  }
+  // Create some shared memory if the queue is empty.
+  if (available_shm_segments_.size() == 0) {
+    // Unretained is safe because the destructor will wait until
+    // |create_shm_thread_| stops.
+    create_shm_thread_.message_loop_proxy()
+        ->PostTask(FROM_HERE,
+                   base::Bind(&RTCVideoDecoder::CreateSHM,
+                              base::Unretained(this),
+                              kMaxInFlightDecodes,
+                              kSharedMemorySegmentBytes));
+  }
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t RTCVideoDecoder::Decode(
+    const webrtc::EncodedImage& inputImage,
+    bool missingFrames,
+    const webrtc::RTPFragmentationHeader* /*fragmentation*/,
+    const webrtc::CodecSpecificInfo* /*codecSpecificInfo*/,
+    int64_t /*renderTimeMs*/) {
+  DVLOG(3) << "Decode";
+
+  base::AutoLock auto_lock(lock_);
+  if (state_ == UNINITIALIZED || decode_complete_callback_ == NULL) {
+    LOG(ERROR) << "The decoder has not initialized.";
+    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
+  }
+  if (state_ == DECODE_ERROR) {
+    LOG(ERROR) << "Decoding error occurred.";
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  if (missingFrames || !inputImage._completeFrame) {
+    DLOG(ERROR) << "Missing or incomplete frames.";
+    // Unlike the SW decoder in libvpx, hw decoder cannot handle broken frames.
+    // Return an error to request a key frame.
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  if (inputImage._frameType == webrtc::kKeyFrame)
+    frame_size_.SetSize(inputImage._encodedWidth, inputImage._encodedHeight);
+
+  // Create buffer metadata.
+  BufferData buffer_data(next_bitstream_buffer_id_,
+                         inputImage._timeStamp,
+                         frame_size_.width(),
+                         frame_size_.height(),
+                         inputImage._length);
+  // Mask against 30 bits, to avoid (undefined) wraparound on signed integer.
+  next_bitstream_buffer_id_ = (next_bitstream_buffer_id_ + 1) & ID_LAST;
+
+  // If the shared memory is available and there are no pending buffers, send
+  // the buffer for decode. If not, save the buffer in the queue for decode
+  // later.
+  scoped_ptr<SHMBuffer> shm_buffer;
+  if (pending_buffers_.size() == 0)
+    shm_buffer = GetSHM_Locked(inputImage._length);
+  if (!shm_buffer) {
+    int32_t result = SaveToPendingBuffers_Locked(inputImage, buffer_data);
+    return result ? WEBRTC_VIDEO_CODEC_OK : WEBRTC_VIDEO_CODEC_ERROR;
+  }
+
+  SaveToDecodeBuffers_Locked(inputImage, shm_buffer.Pass(), buffer_data);
+  vda_loop_proxy_->PostTask(
+      FROM_HERE, base::Bind(&RTCVideoDecoder::RequestBufferDecode, weak_this_));
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t RTCVideoDecoder::RegisterDecodeCompleteCallback(
+    webrtc::DecodedImageCallback* callback) {
+  DVLOG(2) << "RegisterDecodeCompleteCallback";
+  base::AutoLock auto_lock(lock_);
+  decode_complete_callback_ = callback;
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t RTCVideoDecoder::Release() {
+  DVLOG(2) << "Release";
+  // Do not destroy VDA because the decoder will be recycled by
+  // RTCVideoDecoderFactory. Just reset VDA.
+  return Reset();
+}
+
+int32_t RTCVideoDecoder::Reset() {
+  DVLOG(2) << "Reset";
+  base::AutoLock auto_lock(lock_);
+  if (state_ == UNINITIALIZED) {
+    LOG(ERROR) << "Decoder not initialized.";
+    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
+  }
+  if (next_bitstream_buffer_id_ != 0)
+    reset_bitstream_buffer_id_ = next_bitstream_buffer_id_ - 1;
+  else
+    reset_bitstream_buffer_id_ = ID_LAST;
+  // If VDA is already resetting, no need to request the reset again.
+  if (state_ != RESETTING) {
+    state_ = RESETTING;
+    vda_loop_proxy_->PostTask(
+        FROM_HERE, base::Bind(&RTCVideoDecoder::ResetInternal, weak_this_));
+  }
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+void RTCVideoDecoder::NotifyInitializeDone() {
+  DVLOG(2) << "NotifyInitializeDone";
+  NOTREACHED();
+}
+
+void RTCVideoDecoder::ProvidePictureBuffers(uint32 count,
+                                            const gfx::Size& size,
+                                            uint32 texture_target) {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  DVLOG(3) << "ProvidePictureBuffers. texture_target=" << texture_target;
+
+  if (!vda_)
+    return;
+
+  std::vector<uint32> texture_ids;
+  std::vector<gpu::Mailbox> texture_mailboxes;
+  decoder_texture_target_ = texture_target;
+  // Discards the sync point returned here since PictureReady will imply that
+  // the produce has already happened, and the texture is ready for use.
+  if (!factories_->CreateTextures(count,
+                                  size,
+                                  &texture_ids,
+                                  &texture_mailboxes,
+                                  decoder_texture_target_)) {
+    NotifyError(media::VideoDecodeAccelerator::PLATFORM_FAILURE);
+    return;
+  }
+  DCHECK_EQ(count, texture_ids.size());
+  DCHECK_EQ(count, texture_mailboxes.size());
+
+  std::vector<media::PictureBuffer> picture_buffers;
+  for (size_t i = 0; i < texture_ids.size(); ++i) {
+    picture_buffers.push_back(media::PictureBuffer(
+        next_picture_buffer_id_++, size, texture_ids[i], texture_mailboxes[i]));
+    bool inserted = assigned_picture_buffers_.insert(std::make_pair(
+        picture_buffers.back().id(), picture_buffers.back())).second;
+    DCHECK(inserted);
+  }
+  vda_->AssignPictureBuffers(picture_buffers);
+}
+
+void RTCVideoDecoder::DismissPictureBuffer(int32 id) {
+  DVLOG(3) << "DismissPictureBuffer. id=" << id;
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+
+  std::map<int32, media::PictureBuffer>::iterator it =
+      assigned_picture_buffers_.find(id);
+  if (it == assigned_picture_buffers_.end()) {
+    NOTREACHED() << "Missing picture buffer: " << id;
+    return;
+  }
+
+  media::PictureBuffer buffer_to_dismiss = it->second;
+  assigned_picture_buffers_.erase(it);
+
+  std::set<int32>::iterator at_display_it =
+      picture_buffers_at_display_.find(id);
+
+  if (at_display_it == picture_buffers_at_display_.end()) {
+    // We can delete the texture immediately as it's not being displayed.
+    factories_->DeleteTexture(buffer_to_dismiss.texture_id());
+  } else {
+    // Texture in display. Postpone deletion until after it's returned to us.
+    bool inserted = dismissed_picture_buffers_
+        .insert(std::make_pair(id, buffer_to_dismiss)).second;
+    DCHECK(inserted);
+  }
+}
+
+void RTCVideoDecoder::PictureReady(const media::Picture& picture) {
+  DVLOG(3) << "PictureReady";
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+
+  std::map<int32, media::PictureBuffer>::iterator it =
+      assigned_picture_buffers_.find(picture.picture_buffer_id());
+  if (it == assigned_picture_buffers_.end()) {
+    NOTREACHED() << "Missing picture buffer: " << picture.picture_buffer_id();
+    NotifyError(media::VideoDecodeAccelerator::PLATFORM_FAILURE);
+    return;
+  }
+  const media::PictureBuffer& pb = it->second;
+
+  // Create a media::VideoFrame.
+  uint32_t timestamp = 0, width = 0, height = 0;
+  size_t size = 0;
+  GetBufferData(
+      picture.bitstream_buffer_id(), &timestamp, &width, &height, &size);
+  scoped_refptr<media::VideoFrame> frame =
+      CreateVideoFrame(picture, pb, timestamp, width, height, size);
+  bool inserted =
+      picture_buffers_at_display_.insert(picture.picture_buffer_id()).second;
+  DCHECK(inserted);
+
+  // Create a WebRTC video frame.
+  // TODO(wuchengli): make media::VideoFrame an opaque native handle and put it
+  // into WebRTC frame.
+  webrtc::I420VideoFrame decoded_image;
+  decoded_image.CreateEmptyFrame(
+      width, height, width, (width + 1) / 2, (width + 1) / 2);
+  decoded_image.set_timestamp(timestamp);
+
+  // Invoke decode callback. WebRTC expects no frame callback after Release.
+  {
+    base::AutoLock auto_lock(lock_);
+    DCHECK(decode_complete_callback_ != NULL);
+    if (IsBufferAfterReset(picture.bitstream_buffer_id(),
+                           reset_bitstream_buffer_id_)) {
+      decode_complete_callback_->Decoded(decoded_image);
+    }
+  }
+}
+
+scoped_refptr<media::VideoFrame> RTCVideoDecoder::CreateVideoFrame(
+    const media::Picture& picture,
+    const media::PictureBuffer& pb,
+    uint32_t timestamp,
+    uint32_t width,
+    uint32_t height,
+    size_t size) {
+  gfx::Rect visible_rect(width, height);
+  gfx::Size natural_size(width, height);
+  DCHECK(decoder_texture_target_);
+  // Convert timestamp from 90KHz to ms.
+  base::TimeDelta timestamp_ms = base::TimeDelta::FromInternalValue(
+      base::checked_numeric_cast<uint64_t>(timestamp) * 1000 / 90);
+  return media::VideoFrame::WrapNativeTexture(
+      new media::VideoFrame::MailboxHolder(
+          pb.texture_mailbox(),
+          0,  // sync_point
+          media::BindToCurrentLoop(
+              base::Bind(&RTCVideoDecoder::ReusePictureBuffer,
+                         weak_this_,
+                         picture.picture_buffer_id()))),
+      decoder_texture_target_,
+      pb.size(),
+      visible_rect,
+      natural_size,
+      timestamp_ms,
+      base::Bind(&media::GpuVideoDecoder::Factories::ReadPixels,
+                 factories_,
+                 pb.texture_id(),
+                 decoder_texture_target_,
+                 natural_size),
+      base::Closure());
+}
+
+void RTCVideoDecoder::NotifyEndOfBitstreamBuffer(int32 id) {
+  DVLOG(3) << "NotifyEndOfBitstreamBuffer. id=" << id;
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+
+  std::map<int32, SHMBuffer*>::iterator it =
+      bitstream_buffers_in_decoder_.find(id);
+  if (it == bitstream_buffers_in_decoder_.end()) {
+    NotifyError(media::VideoDecodeAccelerator::PLATFORM_FAILURE);
+    NOTREACHED() << "Missing bitstream buffer: " << id;
+    return;
+  }
+
+  {
+    base::AutoLock auto_lock(lock_);
+    PutSHM_Locked(scoped_ptr<SHMBuffer>(it->second));
+  }
+  bitstream_buffers_in_decoder_.erase(it);
+
+  RequestBufferDecode();
+}
+
+void RTCVideoDecoder::NotifyFlushDone() {
+  DVLOG(3) << "NotifyFlushDone";
+  NOTREACHED() << "Unexpected flush done notification.";
+}
+
+void RTCVideoDecoder::NotifyResetDone() {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  DVLOG(3) << "NotifyResetDone";
+
+  if (!vda_)
+    return;
+
+  input_buffer_data_.clear();
+  {
+    base::AutoLock auto_lock(lock_);
+    state_ = INITIALIZED;
+  }
+  // Send the pending buffers for decoding.
+  RequestBufferDecode();
+}
+
+void RTCVideoDecoder::NotifyError(media::VideoDecodeAccelerator::Error error) {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  if (!vda_)
+    return;
+
+  LOG(ERROR) << "VDA Error:" << error;
+  DestroyVDA();
+
+  base::AutoLock auto_lock(lock_);
+  state_ = DECODE_ERROR;
+}
+
+void RTCVideoDecoder::WillDestroyCurrentMessageLoop() {
+  DVLOG(2) << "WillDestroyCurrentMessageLoop";
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  factories_->Abort();
+  weak_factory_.InvalidateWeakPtrs();
+  DestroyVDA();
+}
+
+void RTCVideoDecoder::Initialize(base::WaitableEvent* waiter) {
+  DVLOG(2) << "Initialize";
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  base::MessageLoop::current()->AddDestructionObserver(this);
+  waiter->Signal();
+}
+
+void RTCVideoDecoder::RequestBufferDecode() {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  if (!vda_)
+    return;
+
+  MovePendingBuffersToDecodeBuffers();
+
+  while (CanMoreDecodeWorkBeDone()) {
+    // Get a buffer and data from the queue.
+    SHMBuffer* shm_buffer = NULL;
+    BufferData buffer_data;
+    {
+      base::AutoLock auto_lock(lock_);
+      // Do not request decode if VDA is resetting.
+      if (decode_buffers_.size() == 0 || state_ == RESETTING)
+        return;
+      shm_buffer = decode_buffers_.front().first;
+      buffer_data = decode_buffers_.front().second;
+      decode_buffers_.pop_front();
+      // Drop the buffers before Reset or Release is called.
+      if (!IsBufferAfterReset(buffer_data.bitstream_buffer_id,
+                              reset_bitstream_buffer_id_)) {
+        PutSHM_Locked(scoped_ptr<SHMBuffer>(shm_buffer));
+        continue;
+      }
+    }
+
+    // Create a BitstreamBuffer and send to VDA to decode.
+    media::BitstreamBuffer bitstream_buffer(buffer_data.bitstream_buffer_id,
+                                            shm_buffer->shm->handle(),
+                                            buffer_data.size);
+    bool inserted = bitstream_buffers_in_decoder_
+        .insert(std::make_pair(bitstream_buffer.id(), shm_buffer)).second;
+    DCHECK(inserted);
+    RecordBufferData(buffer_data);
+    vda_->Decode(bitstream_buffer);
+  }
+}
+
+bool RTCVideoDecoder::CanMoreDecodeWorkBeDone() {
+  return bitstream_buffers_in_decoder_.size() < kMaxInFlightDecodes;
+}
+
+bool RTCVideoDecoder::IsBufferAfterReset(int32 id_buffer, int32 id_reset) {
+  if (id_reset == ID_INVALID)
+    return true;
+  int32 diff = id_buffer - id_reset;
+  if (diff <= 0)
+    diff += ID_LAST + 1;
+  return diff < ID_HALF;
+}
+
+void RTCVideoDecoder::SaveToDecodeBuffers_Locked(
+    const webrtc::EncodedImage& input_image,
+    scoped_ptr<SHMBuffer> shm_buffer,
+    const BufferData& buffer_data) {
+  memcpy(shm_buffer->shm->memory(), input_image._buffer, input_image._length);
+  std::pair<SHMBuffer*, BufferData> buffer_pair =
+      std::make_pair(shm_buffer.release(), buffer_data);
+
+  // Store the buffer and the metadata to the queue.
+  decode_buffers_.push_back(buffer_pair);
+}
+
+bool RTCVideoDecoder::SaveToPendingBuffers_Locked(
+    const webrtc::EncodedImage& input_image,
+    const BufferData& buffer_data) {
+  DVLOG(2) << "SaveToPendingBuffers_Locked"
+           << ". pending_buffers size=" << pending_buffers_.size()
+           << ". decode_buffers_ size=" << decode_buffers_.size()
+           << ". available_shm size=" << available_shm_segments_.size();
+  // Queued too many buffers. Something goes wrong.
+  if (pending_buffers_.size() >= kMaxNumOfPendingBuffers) {
+    LOG(WARNING) << "Too many pending buffers!";
+    return false;
+  }
+
+  // Clone the input image and save it to the queue.
+  uint8_t* buffer = new uint8_t[input_image._length];
+  // TODO(wuchengli): avoid memcpy. Extend webrtc::VideoDecoder::Decode()
+  // interface to take a non-const ptr to the frame and add a method to the
+  // frame that will swap buffers with another.
+  memcpy(buffer, input_image._buffer, input_image._length);
+  webrtc::EncodedImage encoded_image(
+      buffer, input_image._length, input_image._length);
+  std::pair<webrtc::EncodedImage, BufferData> buffer_pair =
+      std::make_pair(encoded_image, buffer_data);
+
+  pending_buffers_.push_back(buffer_pair);
+  return true;
+}
+
+void RTCVideoDecoder::MovePendingBuffersToDecodeBuffers() {
+  base::AutoLock auto_lock(lock_);
+  while (pending_buffers_.size() > 0) {
+    // Get a pending buffer from the queue.
+    const webrtc::EncodedImage& input_image = pending_buffers_.front().first;
+    const BufferData& buffer_data = pending_buffers_.front().second;
+
+    // Drop the frame if it comes before Reset or Release.
+    if (!IsBufferAfterReset(buffer_data.bitstream_buffer_id,
+                            reset_bitstream_buffer_id_)) {
+      delete[] input_image._buffer;
+      pending_buffers_.pop_front();
+      continue;
+    }
+    // Get shared memory and save it to decode buffers.
+    scoped_ptr<SHMBuffer> shm_buffer = GetSHM_Locked(input_image._length);
+    if (!shm_buffer)
+      return;
+    SaveToDecodeBuffers_Locked(input_image, shm_buffer.Pass(), buffer_data);
+    delete[] input_image._buffer;
+    pending_buffers_.pop_front();
+  }
+}
+
+void RTCVideoDecoder::ResetInternal() {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  DVLOG(2) << "ResetInternal";
+  if (vda_)
+    vda_->Reset();
+}
+
+void RTCVideoDecoder::ReusePictureBuffer(int64 picture_buffer_id,
+                                         uint32 sync_point) {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  DVLOG(3) << "ReusePictureBuffer. id=" << picture_buffer_id;
+
+  if (!vda_)
+    return;
+
+  CHECK(!picture_buffers_at_display_.empty());
+
+  size_t num_erased = picture_buffers_at_display_.erase(picture_buffer_id);
+  DCHECK(num_erased);
+
+  std::map<int32, media::PictureBuffer>::iterator it =
+      assigned_picture_buffers_.find(picture_buffer_id);
+
+  if (it == assigned_picture_buffers_.end()) {
+    // This picture was dismissed while in display, so we postponed deletion.
+    it = dismissed_picture_buffers_.find(picture_buffer_id);
+    DCHECK(it != dismissed_picture_buffers_.end());
+    factories_->DeleteTexture(it->second.texture_id());
+    dismissed_picture_buffers_.erase(it);
+    return;
+  }
+
+  factories_->WaitSyncPoint(sync_point);
+
+  vda_->ReusePictureBuffer(picture_buffer_id);
+}
+
+void RTCVideoDecoder::DestroyTextures() {
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  std::map<int32, media::PictureBuffer>::iterator it;
+
+  for (it = assigned_picture_buffers_.begin();
+       it != assigned_picture_buffers_.end();
+       ++it) {
+    factories_->DeleteTexture(it->second.texture_id());
+  }
+  assigned_picture_buffers_.clear();
+
+  for (it = dismissed_picture_buffers_.begin();
+       it != dismissed_picture_buffers_.end();
+       ++it) {
+    factories_->DeleteTexture(it->second.texture_id());
+  }
+  dismissed_picture_buffers_.clear();
+}
+
+void RTCVideoDecoder::DestroyVDA() {
+  DVLOG(2) << "DestroyVDA";
+  DCHECK(vda_loop_proxy_->BelongsToCurrentThread());
+  if (vda_)
+    vda_.release()->Destroy();
+  DestroyTextures();
+}
+
+scoped_ptr<RTCVideoDecoder::SHMBuffer> RTCVideoDecoder::GetSHM_Locked(
+    size_t min_size) {
+  // Reuse a SHM if possible.
+  SHMBuffer* ret = NULL;
+  if (!available_shm_segments_.empty() &&
+      available_shm_segments_.back()->size >= min_size) {
+    ret = available_shm_segments_.back();
+    available_shm_segments_.pop_back();
+  }
+  // Post to the child thread to create shared memory if SHM cannot be reused
+  // or the queue is almost empty.
+  if (num_shm_buffers_ < kMaxNumSharedMemorySegments &&
+      (ret == NULL || available_shm_segments_.size() <= 1)) {
+    create_shm_thread_.message_loop_proxy()->PostTask(
+        FROM_HERE,
+        // Unretained is safe because the destructor will wait until
+        // |create_shm_thread_| stops.
+        base::Bind(
+            &RTCVideoDecoder::CreateSHM, base::Unretained(this), 1, min_size));
+  }
+  return scoped_ptr<SHMBuffer>(ret);
+}
+
+void RTCVideoDecoder::PutSHM_Locked(scoped_ptr<SHMBuffer> shm_buffer) {
+  available_shm_segments_.push_back(shm_buffer.release());
+}
+
+void RTCVideoDecoder::CreateSHM(int number, size_t min_size) {
+  DCHECK(create_shm_thread_.message_loop_proxy()->BelongsToCurrentThread());
+  DVLOG(2) << "CreateSHM. size=" << min_size;
+  int number_to_allocate;
+  {
+    base::AutoLock auto_lock(lock_);
+    number_to_allocate =
+        std::min(kMaxNumSharedMemorySegments - num_shm_buffers_, number);
+  }
+  size_t size_to_allocate = std::max(min_size, kSharedMemorySegmentBytes);
+  for (int i = 0; i < number_to_allocate; i++) {
+    base::SharedMemory* shm = factories_->CreateSharedMemory(size_to_allocate);
+    if (shm != NULL) {
+      base::AutoLock auto_lock(lock_);
+      num_shm_buffers_++;
+      PutSHM_Locked(
+          scoped_ptr<SHMBuffer>(new SHMBuffer(shm, size_to_allocate)));
+      // Kick off the decoding.
+      vda_loop_proxy_->PostTask(
+          FROM_HERE,
+          base::Bind(&RTCVideoDecoder::RequestBufferDecode, weak_this_));
+    }
+  }
+}
+
+void RTCVideoDecoder::RecordBufferData(const BufferData& buffer_data) {
+  input_buffer_data_.push_front(buffer_data);
+  // Why this value?  Because why not.  avformat.h:MAX_REORDER_DELAY is 16, but
+  // that's too small for some pathological B-frame test videos.  The cost of
+  // using too-high a value is low (192 bits per extra slot).
+  static const size_t kMaxInputBufferDataSize = 128;
+  // Pop from the back of the list, because that's the oldest and least likely
+  // to be useful in the future data.
+  if (input_buffer_data_.size() > kMaxInputBufferDataSize)
+    input_buffer_data_.pop_back();
+}
+
+void RTCVideoDecoder::GetBufferData(int32 bitstream_buffer_id,
+                                    uint32_t* timestamp,
+                                    uint32_t* width,
+                                    uint32_t* height,
+                                    size_t* size) {
+  for (std::list<BufferData>::iterator it = input_buffer_data_.begin();
+       it != input_buffer_data_.end();
+       ++it) {
+    if (it->bitstream_buffer_id != bitstream_buffer_id)
+      continue;
+    *timestamp = it->timestamp;
+    *width = it->width;
+    *height = it->height;
+    return;
+  }
+  NOTREACHED() << "Missing bitstream buffer id: " << bitstream_buffer_id;
+}
+
+}  // namespace content