Implement software fallback for PPB_VideoDecoder.

content/renderer/pepper/pepper_video_decoder_host.cc

Index: content/renderer/pepper/pepper_video_decoder_host.cc
diff --git a/content/renderer/pepper/pepper_video_decoder_host.cc b/content/renderer/pepper/pepper_video_decoder_host.cc
index 16019f720b29e4e6be4a8e1d236043dfecd3802e..db3c114889121b90e178cdf9c4540235f3ddbd9e 100644
--- a/content/renderer/pepper/pepper_video_decoder_host.cc
+++ b/content/renderer/pepper/pepper_video_decoder_host.cc
@@ -2,6 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <GLES2/gl2extchromium.h>
+
 #include "content/renderer/pepper/pepper_video_decoder_host.h"
 
 #include "base/bind.h"
@@ -12,6 +16,9 @@
 #include "content/renderer/pepper/ppb_graphics_3d_impl.h"
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/render_view_impl.h"
+#include "gpu/command_buffer/client/gles2_implementation.h"
+#include "media/base/decoder_buffer.h"
+#include "media/filters/ffmpeg_video_decoder.h"
 #include "media/video/picture.h"
 #include "media/video/video_decode_accelerator.h"
 #include "ppapi/c/pp_completion_callback.h"
@@ -22,6 +29,8 @@
 #include "ppapi/proxy/video_decoder_constants.h"
 #include "ppapi/thunk/enter.h"
 #include "ppapi/thunk/ppb_graphics_3d_api.h"
+#include "third_party/libyuv/include/libyuv.h"
+#include "webkit/common/gpu/context_provider_web_context.h"
 
 using ppapi::proxy::SerializedHandle;
 using ppapi::thunk::EnterResourceNoLock;
@@ -65,6 +74,534 @@ media::VideoCodecProfile PepperToMediaVideoProfile(PP_VideoProfile profile) {
 
 }  // namespace
 
+// This wrapper class calls methods on a media::VideoDecoder on the media thread
+// and relays results back to the host on the main thread. It should be created,
+// used, and destroyed on the main (render) thread.
+class SoftwareDecoder {
+ public:
+  explicit SoftwareDecoder(PepperVideoDecoderHost* host);
+
+  void Initialize(media::VideoCodecProfile profile);
+  void Decode(uint32_t decode_id,
+              const scoped_refptr<media::DecoderBuffer>& buffer);
+  void AssignTextures(const std::vector<uint32_t>& texture_ids);
+  void RecycleTexture(uint32_t texture_id);
+  void Flush();
+  void Reset();
+  void Destroy();
+
+ protected:
+  // Do not delete directly; use Destroy() or own it with a scoped_ptr, which
+  // will Destroy() it properly by default.
+  ~SoftwareDecoder();
+
+ private:
+  struct PendingDecode {
+    PendingDecode(uint32_t decode_id,
+                  const scoped_refptr<media::DecoderBuffer>& buffer);
+    ~PendingDecode();
+
+    uint32_t decode_id;
+    scoped_refptr<media::DecoderBuffer> buffer;
+  };
+
+  struct PendingFrame {
+    PendingFrame(uint32_t decode_id, const gfx::Size& size);
+    ~PendingFrame();
+
+    uint32_t decode_id;
+    gfx::Size size;
+    std::vector<uint8_t> pixels;
+  };
+
+  void InitializeOnMediaThread(media::VideoDecoderConfig config);
+  void PipelineStatusOnMediaThread(media::PipelineStatus status);
+  void PipelineStatusOnMainThread(media::PipelineStatus status);
+
+  void ReceiveBufferOnMediaThread(uint32_t decode_id,
+                                  scoped_refptr<media::DecoderBuffer> buffer);
+  void DecodeOnMediaThread();
+  void ConvertFrameOnMediaThread(uint32_t decode_id,
+                                 media::VideoDecoder::Status status,
+                                 const scoped_refptr<media::VideoFrame>& frame);
+  void ReceiveFrameOnMainThread(media::VideoDecoder::Status status,
+                                scoped_ptr<PendingFrame> frame);
+  void SendPicturesOnMainThread();
+
+  void DoResetOnMediaThread();
+  void ResetCompleteOnMediaThread();
+  void ResetCompleteOnMainThread();
+
+  void DestroyOnMediaThread();
+  void DestroyOnMainThread();
+
+  void DismissTexture(uint32_t texture_id);
+  void DeleteTexture(uint32_t texture_id);
+  void FlushCommandBuffer();
+
+  // These members are accessed only on the main thread.
+
+  PepperVideoDecoderHost* host_;
+  scoped_refptr<base::MessageLoopProxy> media_message_loop_;
+  scoped_refptr<webkit::gpu::ContextProviderWebContext> context_provider_;
+  // The current decoded frame size.
+  gfx::Size texture_size_;
+  // Map that takes the plugin's GL texture id to the renderer's GL texture id.
+  typedef base::hash_map<uint32_t, uint32_t> TextureIdMap;
+  TextureIdMap texture_id_map_;
+  // Available textures (these are plugin ids.)
+  std::vector<uint32_t> available_textures_;
+  // Track textures that are no longer needed (these are plugin ids.)
+  typedef base::hash_set<uint32_t> TextureIdSet;
+  TextureIdSet textures_to_dismiss_;
+  // Mailboxes for pending texture requests, to write to plugin's textures.
+  std::vector<gpu::Mailbox> pending_texture_mailboxes_;
+  // Queue of pending decoded frames. These have been converted to RGB, and
+  // await upload to a GL texture.
+  typedef std::queue<PendingFrame*> PendingFrameQueue;
+  PendingFrameQueue pending_frames_;
+  uint32_t num_pending_decodes_;
+  bool flushing_;
+  bool resetting_;

[dmichael (off chromium), 2014/06/03 22:27:47]

suggestion: Might be clearer to use a 3-state enum. (something like normal,
resetting, flushing)

[bbudge, 2014/06/04 14:10:12]

UNITIALIZED, DECODING, FLUSHING, RESETTING.
Done.

+
+  // These members are accessed only on the media thread.
+
+  scoped_ptr<media::VideoDecoder> decoder_;
+  scoped_refptr<base::MessageLoopProxy> main_message_loop_;
+  // Queue of decodes waiting for the decoder.
+  typedef std::queue<PendingDecode> PendingDecodeQueue;
+  PendingDecodeQueue pending_decodes_;

[dmichael (off chromium), 2014/06/03 22:27:47]

This is a bit hard to follow with the mix of operations and data members on the
two threads. Without thinking too hard about it, I wonder if it would be any
cleaner to split in to two classes? The outer SoftwareDecoder would live on the
main thread. There could be an inner Delegate (or whatever) that handles all the
work on the Media thread.

SoftwareDecoder could provide SoftwareDecoder::Delegate with a WeakPtr. When
Delegate needs to PostTask to SoftwareDecoder, it could just use the WeakPtr. So
long as the WeakPtr is always dereferenced on the main thread, it's safe to use
this way. That might allow you to do away with the "if (!host_)" stuff.

I also think the destruction semantics could be simpler this way. The
SoftwareDecode can just let itself be deleted, and use something like DeleteSoon
to shutdown the Delegate part on the media thread.

WDYT?

[bbudge, 2014/06/04 14:10:12]

I moved SoftwareDecoder to its own files (video_decoder_proxy.*) and split the
media thread stuff into a child Delegate class. This helps keep the thread
separation clearer.

I don't think it's necessary to make Delegate heap allocated. I can just embed
it in its parent VideoDecoderProxy class.

As for the 'host_' pointer, I'm trying to avoid the need for making
PepperVideoDecoderHost support weak pointers. If you'd like, I can try to make
the destruction process clearer with more comments. The process is:
1) the host scoped_ptr causes Destroy to be called in VDP.
2) VDP sets its host_ ptr to NULL, and calls the delegate Destroy (media
thread).
3) The Delegate calls Destroy, calling all callbacks on media thread to
complete, potentially posting tasks to the main thread.
4) Delegate posts the final task on main thread, to call VDP OnDestroyComplete.
5) VDP delete this.

[dmichael (off chromium), 2014/06/04 15:47:29]

Do you mean you don't want to inherit SupportsWeakPtr? I'd agree with that. But
you can just pass a WeakPtr to the Delegate when you create it, and it can
always use that when posting a task back to the SoftwareDecoder on the main
thread. That, or you can use base::Callback<>s instead, and the Delegate
wouldn't even need to have knowledge of the class it's calling. The
SoftwareDecoder would be responsible for binding them to the right methods with
WeakPtrs. This has the additional advantage that all those methods can be
private, and you don't need friendship.

The downside with using Callback<> is that it adds more indirection, so might
make things harder to follow. So I'm not hard over on that. But I suspect at
least using WeakPtr would be a little cleaner than checking host_ and making
SoftwareDecoder live beyond its useful life.

WDYT?

[bbudge, 2014/06/04 20:52:46]

Delegate now references VideoDecoderProxy (formerly SoftwareDecoder) via
WeakPtr.

We can't use callbacks since 'replies' don't correspond 1:1 with calls (e.g.
PictureReady).

[dmichael (off chromium), 2014/06/04 21:03:07]

FYI, base::Callbacks have no restriction on the number of times they're called.
You could map them to the same methods you already have defined and pass
base::Callback<>s instead of a WeakPtr. Only advantage being the Delegate
doesn't need to directly refer to the class. Can be better for unit testing, for
example. But it would increase indirection so might make the code slightly
harder to follow.

I haven't looked at the current patchset yet; it's likely it's good this way.
But if you think base::Callback would be better, it's probably feasible to do it
that way.

+
+  DISALLOW_COPY_AND_ASSIGN(SoftwareDecoder);
+};
+
+SoftwareDecoder::PendingDecode::PendingDecode(
+    uint32_t decode_id,
+    const scoped_refptr<media::DecoderBuffer>& buffer)
+    : decode_id(decode_id), buffer(buffer) {
+}
+
+SoftwareDecoder::PendingDecode::~PendingDecode() {
+}
+
+SoftwareDecoder::PendingFrame::PendingFrame(uint32_t decode_id,
+                                            const gfx::Size& size)
+    : decode_id(decode_id),
+      size(size),
+      pixels(size.width() * size.height() * 4) {
+}
+
+SoftwareDecoder::PendingFrame::~PendingFrame() {
+}
+
+SoftwareDecoder::SoftwareDecoder(PepperVideoDecoderHost* host)
+    : host_(host),
+      media_message_loop_(
+          RenderThreadImpl::current()->GetMediaThreadMessageLoopProxy()),
+      context_provider_(
+          RenderThreadImpl::current()->SharedMainThreadContextProvider()),
+      num_pending_decodes_(0),
+      flushing_(false),
+      resetting_(false),
+      main_message_loop_(base::MessageLoopProxy::current()) {
+  DCHECK(host_);
+  DCHECK(main_message_loop_);
+  DCHECK(media_message_loop_);
+  DCHECK(context_provider_);
+}
+
+SoftwareDecoder::~SoftwareDecoder() {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(!host_);
+  // Delete any remaining video frames.
+  while (!pending_frames_.empty()) {
+    delete pending_frames_.front();
+    pending_frames_.pop();
+  }
+  // Delete any remaining textures.
+  TextureIdMap::iterator it = texture_id_map_.begin();
+  for (; it != texture_id_map_.end(); ++it)
+    DeleteTexture(it->second);
+
+  FlushCommandBuffer();
+}
+
+void SoftwareDecoder::Initialize(media::VideoCodecProfile profile) {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(!decoder_);
+  media::VideoCodec codec = media::kUnknownVideoCodec;
+  if (profile <= media::H264PROFILE_MAX)
+    codec = media::kCodecH264;
+  else if (profile <= media::VP8PROFILE_MAX)
+    codec = media::kCodecVP8;
+  DCHECK_NE(codec, media::kUnknownVideoCodec);
+
+  media::VideoDecoderConfig config(
+      codec,
+      profile,
+      media::VideoFrame::YV12,
+      gfx::Size(32, 24),  // Small sizes that won't fail.
+      gfx::Rect(32, 24),
+      gfx::Size(32, 24),
+      NULL /* extra_data */,
+      0 /* extra_data_size */,
+      false /* decryption */);
+
+  decoder_.reset(new media::FFmpegVideoDecoder(media_message_loop_));
+
+  media_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::InitializeOnMediaThread,
+                 base::Unretained(this),
+                 config));
+}
+
+void SoftwareDecoder::Decode(
+    uint32_t decode_id,
+    const scoped_refptr<media::DecoderBuffer>& buffer) {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  DCHECK(!resetting_ && !flushing_);
+
+  num_pending_decodes_++;
+
+  media_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::ReceiveBufferOnMediaThread,
+                 base::Unretained(this),
+                 decode_id,
+                 buffer));
+}
+
+void SoftwareDecoder::AssignTextures(const std::vector<uint32_t>& texture_ids) {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  DCHECK(texture_ids.size());
+  DCHECK_EQ(texture_ids.size(), pending_texture_mailboxes_.size());
+  uint32_t num_textures = static_cast<GLuint>(texture_ids.size());
+  std::vector<uint32_t> local_texture_ids(num_textures);
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  gles2->GenTextures(num_textures, &local_texture_ids.front());
+  for (uint32_t i = 0; i < num_textures; i++) {
+    gles2->ActiveTexture(GL_TEXTURE0);
+    gles2->BindTexture(GL_TEXTURE_2D, local_texture_ids[i]);
+    gles2->ConsumeTextureCHROMIUM(GL_TEXTURE_2D,
+                                  pending_texture_mailboxes_[i].name);
+    // Map the plugin texture id to the local texture id.
+    texture_id_map_.insert(
+        std::make_pair(texture_ids[i], local_texture_ids[i]));
+  }
+  pending_texture_mailboxes_.clear();
+  available_textures_.insert(
+      available_textures_.end(), texture_ids.begin(), texture_ids.end());
+  SendPicturesOnMainThread();
+}
+
+void SoftwareDecoder::RecycleTexture(uint32_t texture_id) {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  if (textures_to_dismiss_.find(texture_id) != textures_to_dismiss_.end()) {
+    DismissTexture(texture_id);
+  } else if (texture_id_map_.find(texture_id) != texture_id_map_.end()) {
+    available_textures_.push_back(texture_id);
+    SendPicturesOnMainThread();
+  } else {
+    NOTREACHED();
+  }
+}
+
+void SoftwareDecoder::Flush() {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  DCHECK(!resetting_ && !flushing_);
+  flushing_ = true;
+}
+
+void SoftwareDecoder::Reset() {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  DCHECK(!resetting_ && !flushing_);
+  resetting_ = true;
+  media_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::DoResetOnMediaThread,
+                 base::Unretained(this)));
+}
+
+void SoftwareDecoder::Destroy() {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(decoder_);
+  DCHECK(host_);
+  host_ = NULL;
+  media_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::DestroyOnMediaThread,
+                 base::Unretained(this)));
+}
+
+void SoftwareDecoder::InitializeOnMediaThread(
+    media::VideoDecoderConfig config) {
+  DCHECK(decoder_);
+  decoder_->Initialize(config,
+                       true /* low_delay */,
+                       base::Bind(&SoftwareDecoder::PipelineStatusOnMediaThread,
+                                  base::Unretained(this)));
+}
+
+void SoftwareDecoder::PipelineStatusOnMediaThread(
+    media::PipelineStatus status) {
+  if (!host_)
+    return;
+  main_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::PipelineStatusOnMainThread,
+                 base::Unretained(this),
+                 status));
+}
+
+void SoftwareDecoder::PipelineStatusOnMainThread(media::PipelineStatus status) {
+  if (!host_)
+    return;
+  int32_t result;
+  switch (status) {
+    case media::PIPELINE_OK:
+      result = PP_OK;
+      break;
+    case media::DECODER_ERROR_NOT_SUPPORTED:
+      result = PP_ERROR_NOTSUPPORTED;
+      break;
+    default:
+      result = PP_ERROR_FAILED;
+      break;
+  }
+  host_->OnInitializeComplete(result);
+}
+
+void SoftwareDecoder::ReceiveBufferOnMediaThread(
+    uint32_t decode_id,
+    scoped_refptr<media::DecoderBuffer> buffer) {
+  bool decoder_busy = !pending_decodes_.empty();
+  pending_decodes_.push(PendingDecode(decode_id, buffer));
+  if (!decoder_busy)
+    DecodeOnMediaThread();
+}
+
+void SoftwareDecoder::DecodeOnMediaThread() {
+  DCHECK(!pending_decodes_.empty());
+  PendingDecode& next_decode = pending_decodes_.front();
+  decoder_->Decode(next_decode.buffer,
+                   base::Bind(&SoftwareDecoder::ConvertFrameOnMediaThread,
+                              base::Unretained(this),
+                              next_decode.decode_id));
+  pending_decodes_.pop();
+}
+
+void SoftwareDecoder::ConvertFrameOnMediaThread(
+    uint32_t decode_id,
+    media::VideoDecoder::Status status,
+    const scoped_refptr<media::VideoFrame>& frame) {
+  if (!host_)
+    return;
+  scoped_ptr<PendingFrame> pending_frame(
+      new PendingFrame(decode_id, gfx::Size()));
+  if (frame) {
+    pending_frame->size = frame->coded_size();
+    pending_frame->pixels.resize(frame->coded_size().width() *
+                                 frame->coded_size().height() * 4);
+    // Convert the decoded frame to ARGB pixels.
+    libyuv::I420ToARGB(frame->data(media::VideoFrame::kYPlane),
+                       frame->stride(media::VideoFrame::kYPlane),
+                       frame->data(media::VideoFrame::kUPlane),
+                       frame->stride(media::VideoFrame::kUPlane),
+                       frame->data(media::VideoFrame::kVPlane),
+                       frame->stride(media::VideoFrame::kVPlane),
+                       &pending_frame->pixels.front(),
+                       frame->coded_size().width() * 4,
+                       frame->coded_size().width(),
+                       frame->coded_size().height());
+  }
+
+  main_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::ReceiveFrameOnMainThread,
+                 base::Unretained(this),
+                 status,
+                 base::Passed(&pending_frame)));
+
+  if (!pending_decodes_.empty())
+    DecodeOnMediaThread();
+}
+
+void SoftwareDecoder::ReceiveFrameOnMainThread(
+    media::VideoDecoder::Status status,
+    scoped_ptr<PendingFrame> frame) {
+  DCHECK(RenderThreadImpl::current());
+  if (!host_)
+    return;
+
+  num_pending_decodes_--;
+
+  if (frame->pixels.size()) {
+    if (texture_size_ != frame->size) {
+      // If the size has changed, all current textures must be dismissed. Add
+      // all textures to |textures_to_dismiss_| and dismiss any that aren't in
+      // use by the plugin. We dismiss the rest as they are recycled.
+      for (TextureIdMap::const_iterator it = texture_id_map_.begin();
+           it != texture_id_map_.end();
+           ++it) {
+        textures_to_dismiss_.insert(it->second);
+      }
+      for (std::vector<uint32_t>::const_iterator it =
+               available_textures_.begin();
+           it != available_textures_.end();
+           ++it) {
+        DismissTexture(*it);
+      }
+      available_textures_.clear();
+      FlushCommandBuffer();
+
+      DCHECK(pending_texture_mailboxes_.empty());
+      const uint32_t num_textures = 8;
+      for (uint32_t i = 0; i < num_textures; i++)
+        pending_texture_mailboxes_.push_back(gpu::Mailbox::Generate());
+
+      host_->RequestTextures(
+          num_textures, frame->size, GL_TEXTURE_2D, pending_texture_mailboxes_);
+      texture_size_ = frame->size;
+    }
+
+    pending_frames_.push(frame.release());
+    SendPicturesOnMainThread();
+  } else {
+    host_->NotifyEndOfBitstreamBuffer(frame->decode_id);
+  }
+
+  switch (status) {
+    case media::VideoDecoder::kOk:
+    case media::VideoDecoder::kAborted:
+      break;
+    case media::VideoDecoder::kNotEnoughData:

[igorc, 2014/06/03 20:26:32]

This is not an error in H264 case when we feed individual NALU's. Together with
not requiring entire frames, this fixes H264 example.

[bbudge, 2014/06/03 20:59:20]

Do you mean that we should silently ignore this error?

[bbudge, 2014/06/04 14:10:12]

Changed to not call NotifyError on kNotEnoughData.

+      host_->NotifyError(PP_ERROR_MALFORMED_INPUT);
+      break;
+    case media::VideoDecoder::kDecodeError:
+    case media::VideoDecoder::kDecryptError:
+      host_->NotifyError(PP_ERROR_RESOURCE_FAILED);
+      break;
+      // No default case, to catch unhandled status values.
+  }
+}
+
+void SoftwareDecoder::SendPicturesOnMainThread() {
+  DCHECK(RenderThreadImpl::current());
+  if (!host_)
+    return;
+  while (!pending_frames_.empty() && !available_textures_.empty()) {
+    scoped_ptr<PendingFrame> frame(pending_frames_.front());
+    pending_frames_.pop();
+
+    uint32_t texture_id = available_textures_.back();
+    available_textures_.pop_back();
+
+    uint32_t local_texture_id = texture_id_map_[texture_id];
+    gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+    gles2->ActiveTexture(GL_TEXTURE0);
+    gles2->BindTexture(GL_TEXTURE_2D, local_texture_id);
+    gles2->TexImage2D(GL_TEXTURE_2D,
+                      0,
+                      GL_RGBA,
+                      texture_size_.width(),
+                      texture_size_.height(),
+                      0,
+                      GL_RGBA,
+                      GL_UNSIGNED_BYTE,
+                      &frame->pixels.front());
+
+    host_->NotifyEndOfBitstreamBuffer(frame->decode_id);
+    host_->PictureReady(media::Picture(texture_id, frame->decode_id));
+  }
+
+  FlushCommandBuffer();
+
+  if (flushing_ && !num_pending_decodes_ && pending_frames_.empty()) {
+    flushing_ = false;
+    host_->NotifyFlushDone();
+  }
+}
+
+void SoftwareDecoder::DoResetOnMediaThread() {
+  decoder_->Reset(base::Bind(&SoftwareDecoder::ResetCompleteOnMediaThread,
+                             base::Unretained(this)));
+}
+
+void SoftwareDecoder::ResetCompleteOnMediaThread() {
+  // Cancel all remaining decodes, and notify the host so it can free the shm
+  // buffers. We'll clear pending frames on the main thread.
+  while (!pending_decodes_.empty()) {
+    PendingDecode& next_decode = pending_decodes_.front();
+    scoped_ptr<PendingFrame> pending_frame(
+        new PendingFrame(next_decode.decode_id, gfx::Size()));
+    main_message_loop_->PostTask(
+        FROM_HERE,
+        base::Bind(&SoftwareDecoder::ReceiveFrameOnMainThread,
+                   base::Unretained(this),
+                   media::VideoDecoder::kAborted,
+                   base::Passed(&pending_frame)));
+    pending_decodes_.pop();
+  }
+  main_message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&SoftwareDecoder::ResetCompleteOnMainThread,
+                 base::Unretained(this)));
+}
+
+void SoftwareDecoder::ResetCompleteOnMainThread() {
+  if (!host_)
+    return;
+  while (!pending_frames_.empty()) {
+    scoped_ptr<PendingFrame> frame(pending_frames_.front());
+    host_->NotifyEndOfBitstreamBuffer(frame->decode_id);
+    pending_frames_.pop();
+  }
+
+  resetting_ = false;
+  host_->NotifyResetDone();
+}
+
+void SoftwareDecoder::DestroyOnMediaThread() {
+  DCHECK(decoder_);
+  decoder_->Stop();
+  // All callbacks have been called on the media thread, and thus all tasks
+  // posted for the main thread. This is our last task for the main thread.
+  main_message_loop_->PostTask(FROM_HERE,
+                               base::Bind(&SoftwareDecoder::DestroyOnMainThread,
+                                          base::Unretained(this)));
+}
+
+void SoftwareDecoder::DestroyOnMainThread() {
+  DCHECK(RenderThreadImpl::current());
+  DCHECK(!host_);
+  delete this;
+}
+
+void SoftwareDecoder::DismissTexture(uint32_t texture_id) {
+  DCHECK(host_);
+  textures_to_dismiss_.erase(texture_id);
+  DCHECK(texture_id_map_.find(texture_id) != texture_id_map_.end());
+  DeleteTexture(texture_id_map_[texture_id]);
+  texture_id_map_.erase(texture_id);
+  host_->DismissPictureBuffer(texture_id);
+}
+
+void SoftwareDecoder::DeleteTexture(uint32_t texture_id) {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  gles2->DeleteTextures(1, &texture_id);
+}
+
+void SoftwareDecoder::FlushCommandBuffer() {
+  DCHECK(RenderThreadImpl::current());
+  context_provider_->ContextGL()->Flush();
+}
+

[dmichael (off chromium), 2014/06/03 22:27:46]

I think this class should be in its own file.

[bbudge, 2014/06/04 14:10:12]

Done.

 PepperVideoDecoderHost::PendingDecode::PendingDecode(
     uint32_t shm_id,
     const ppapi::host::ReplyMessageContext& reply_context)
@@ -119,9 +656,10 @@ int32_t PepperVideoDecoderHost::OnHostMsgInitialize(
       graphics_context.host_resource(), true);
   if (enter_graphics.failed())
     return PP_ERROR_FAILED;
-  graphics3d_ = static_cast<PPB_Graphics3D_Impl*>(enter_graphics.object());
+  PPB_Graphics3D_Impl* graphics3d =
+      static_cast<PPB_Graphics3D_Impl*>(enter_graphics.object());
 
-  int command_buffer_route_id = graphics3d_->GetCommandBufferRouteId();
+  int command_buffer_route_id = graphics3d->GetCommandBufferRouteId();
   if (!command_buffer_route_id)
     return PP_ERROR_FAILED;
 
@@ -129,7 +667,7 @@ int32_t PepperVideoDecoderHost::OnHostMsgInitialize(
 
   // This is not synchronous, but subsequent IPC messages will be buffered, so
   // it is okay to immediately send IPC messages through the returned channel.
-  GpuChannelHost* channel = graphics3d_->channel();
+  GpuChannelHost* channel = graphics3d->channel();
   DCHECK(channel);
   decoder_ = channel->CreateVideoDecoder(command_buffer_route_id);
   if (decoder_ && decoder_->Initialize(media_profile, this)) {
@@ -138,8 +676,14 @@ int32_t PepperVideoDecoderHost::OnHostMsgInitialize(
   }
   decoder_.reset();
 
-  // TODO(bbudge) Implement software fallback.
-  return PP_ERROR_NOTSUPPORTED;
+  if (!allow_software_fallback)
+    return PP_ERROR_NOTSUPPORTED;
+
+  software_decoder_.reset(new SoftwareDecoder(this));
+  initialize_reply_context_ = context->MakeReplyMessageContext();
+  software_decoder_->Initialize(media_profile);
+
+  return PP_OK_COMPLETIONPENDING;
 }
 
 int32_t PepperVideoDecoderHost::OnHostMsgGetShm(
@@ -208,7 +752,7 @@ int32_t PepperVideoDecoderHost::OnHostMsgDecode(
     int32_t decode_id) {
   if (!initialized_)
     return PP_ERROR_FAILED;
-  DCHECK(decoder_);
+  DCHECK(decoder_ || software_decoder_);
   // |shm_id| is just an index into shm_buffers_. Make sure it's in range.
   if (static_cast<size_t>(shm_id) >= shm_buffers_.size())
     return PP_ERROR_FAILED;
@@ -226,8 +770,14 @@ int32_t PepperVideoDecoderHost::OnHostMsgDecode(
       decode_id, PendingDecode(shm_id, context->MakeReplyMessageContext())));
 
   shm_buffer_busy_[shm_id] = true;
-  decoder_->Decode(
-      media::BitstreamBuffer(decode_id, shm_buffers_[shm_id]->handle(), size));
+  base::SharedMemory* shm = shm_buffers_[shm_id];
+  if (decoder_) {
+    decoder_->Decode(media::BitstreamBuffer(decode_id, shm->handle(), size));
+  } else {
+    software_decoder_->Decode(decode_id,
+                              media::DecoderBuffer::CopyFrom(
+                                  static_cast<uint8_t*>(shm->memory()), size));
+  }
 
   return PP_OK_COMPLETIONPENDING;
 }
@@ -238,17 +788,21 @@ int32_t PepperVideoDecoderHost::OnHostMsgAssignTextures(
     const std::vector<uint32_t>& texture_ids) {
   if (!initialized_)
     return PP_ERROR_FAILED;
-  DCHECK(decoder_);
-
-  std::vector<media::PictureBuffer> picture_buffers;
-  for (uint32 i = 0; i < texture_ids.size(); i++) {
-    media::PictureBuffer buffer(
-        texture_ids[i],  // Use the texture_id to identify the buffer.
-        gfx::Size(size.width, size.height),
-        texture_ids[i]);
-    picture_buffers.push_back(buffer);
+  DCHECK(decoder_ || software_decoder_);
+
+  if (decoder_) {
+    std::vector<media::PictureBuffer> picture_buffers;
+    for (uint32 i = 0; i < texture_ids.size(); i++) {
+      media::PictureBuffer buffer(
+          texture_ids[i],  // Use the texture_id to identify the buffer.
+          gfx::Size(size.width, size.height),
+          texture_ids[i]);
+      picture_buffers.push_back(buffer);
+    }
+    decoder_->AssignPictureBuffers(picture_buffers);
+  } else {
+    software_decoder_->AssignTextures(texture_ids);
   }
-  decoder_->AssignPictureBuffers(picture_buffers);
   return PP_OK;
 }
 
@@ -257,11 +811,14 @@ int32_t PepperVideoDecoderHost::OnHostMsgRecyclePicture(
     uint32_t texture_id) {
   if (!initialized_)
     return PP_ERROR_FAILED;
-  DCHECK(decoder_);
+  DCHECK(decoder_ || software_decoder_);
   if (reset_reply_context_.is_valid())
     return PP_ERROR_FAILED;
-
-  decoder_->ReusePictureBuffer(texture_id);
+  if (decoder_) {
+    decoder_->ReusePictureBuffer(texture_id);
+  } else {
+    software_decoder_->RecycleTexture(texture_id);
+  }
 
   return PP_OK;
 }
@@ -270,12 +827,15 @@ int32_t PepperVideoDecoderHost::OnHostMsgFlush(
     ppapi::host::HostMessageContext* context) {
   if (!initialized_)
     return PP_ERROR_FAILED;
-  DCHECK(decoder_);
+  DCHECK(decoder_ || software_decoder_);
   if (flush_reply_context_.is_valid() || reset_reply_context_.is_valid())
     return PP_ERROR_FAILED;
 
   flush_reply_context_ = context->MakeReplyMessageContext();
-  decoder_->Flush();
+  if (decoder_)
+    decoder_->Flush();
+  else
+    software_decoder_->Flush();
 
   return PP_OK_COMPLETIONPENDING;
 }
@@ -284,12 +844,15 @@ int32_t PepperVideoDecoderHost::OnHostMsgReset(
     ppapi::host::HostMessageContext* context) {
   if (!initialized_)
     return PP_ERROR_FAILED;
-  DCHECK(decoder_);
+  DCHECK(decoder_ || software_decoder_);
   if (flush_reply_context_.is_valid() || reset_reply_context_.is_valid())
     return PP_ERROR_FAILED;
 
   reset_reply_context_ = context->MakeReplyMessageContext();
-  decoder_->Reset();
+  if (decoder_)
+    decoder_->Reset();
+  else
+    software_decoder_->Reset();
 
   return PP_OK_COMPLETIONPENDING;
 }
@@ -298,17 +861,13 @@ void PepperVideoDecoderHost::ProvidePictureBuffers(
     uint32 requested_num_of_buffers,
     const gfx::Size& dimensions,
     uint32 texture_target) {
-  DCHECK(RenderThreadImpl::current());
-  host()->SendUnsolicitedReply(
-      pp_resource(),
-      PpapiPluginMsg_VideoDecoder_RequestTextures(
-          requested_num_of_buffers,
-          PP_MakeSize(dimensions.width(), dimensions.height()),
-          texture_target));
+  RequestTextures(requested_num_of_buffers,
+                  dimensions,
+                  texture_target,
+                  std::vector<gpu::Mailbox>());
 }
 
 void PepperVideoDecoderHost::PictureReady(const media::Picture& picture) {
-  DCHECK(RenderThreadImpl::current());
   host()->SendUnsolicitedReply(
       pp_resource(),
       PpapiPluginMsg_VideoDecoder_PictureReady(picture.bitstream_buffer_id(),
@@ -316,15 +875,40 @@ void PepperVideoDecoderHost::PictureReady(const media::Picture& picture) {
 }
 
 void PepperVideoDecoderHost::DismissPictureBuffer(int32 picture_buffer_id) {
-  DCHECK(RenderThreadImpl::current());
   host()->SendUnsolicitedReply(
       pp_resource(),
       PpapiPluginMsg_VideoDecoder_DismissPicture(picture_buffer_id));
 }
 
+void PepperVideoDecoderHost::NotifyEndOfBitstreamBuffer(
+    int32 bitstream_buffer_id) {
+  PendingDecodeMap::iterator it = pending_decodes_.find(bitstream_buffer_id);
+  if (it == pending_decodes_.end()) {
+    NOTREACHED();
+    return;
+  }
+  const PendingDecode& pending_decode = it->second;
+  host()->SendReply(
+      pending_decode.reply_context,
+      PpapiPluginMsg_VideoDecoder_DecodeReply(pending_decode.shm_id));
+  shm_buffer_busy_[pending_decode.shm_id] = false;
+  pending_decodes_.erase(it);
+}
+
+void PepperVideoDecoderHost::NotifyFlushDone() {
+  host()->SendReply(flush_reply_context_,
+                    PpapiPluginMsg_VideoDecoder_FlushReply());
+  flush_reply_context_ = ppapi::host::ReplyMessageContext();
+}
+
+void PepperVideoDecoderHost::NotifyResetDone() {
+  host()->SendReply(reset_reply_context_,
+                    PpapiPluginMsg_VideoDecoder_ResetReply());
+  reset_reply_context_ = ppapi::host::ReplyMessageContext();
+}
+
 void PepperVideoDecoderHost::NotifyError(
     media::VideoDecodeAccelerator::Error error) {
-  DCHECK(RenderThreadImpl::current());
   int32_t pp_error = PP_ERROR_FAILED;
   switch (error) {
     case media::VideoDecodeAccelerator::UNREADABLE_INPUT:
@@ -338,38 +922,45 @@ void PepperVideoDecoderHost::NotifyError(
       break;
     // No default case, to catch unhandled enum values.
   }
-  host()->SendUnsolicitedReply(
-      pp_resource(), PpapiPluginMsg_VideoDecoder_NotifyError(pp_error));
+  NotifyError(pp_error);
 }
 
-void PepperVideoDecoderHost::NotifyResetDone() {
-  DCHECK(RenderThreadImpl::current());
-  host()->SendReply(reset_reply_context_,
-                    PpapiPluginMsg_VideoDecoder_ResetReply());
-  reset_reply_context_ = ppapi::host::ReplyMessageContext();
+void PepperVideoDecoderHost::OnInitializeComplete(int32_t result) {
+  if (!initialized_) {
+    initialized_ = true;
+    initialize_reply_context_.params.set_result(result);
+    host()->SendReply(initialize_reply_context_,
+                      PpapiPluginMsg_VideoDecoder_InitializeReply());
+  }
 }
 
-void PepperVideoDecoderHost::NotifyEndOfBitstreamBuffer(
-    int32 bitstream_buffer_id) {
+void PepperVideoDecoderHost::RequestTextures(
+    uint32 requested_num_of_buffers,
+    const gfx::Size& dimensions,
+    uint32 texture_target,
+    const std::vector<gpu::Mailbox>& mailboxes) {
   DCHECK(RenderThreadImpl::current());
-  PendingDecodeMap::iterator it = pending_decodes_.find(bitstream_buffer_id);
-  if (it == pending_decodes_.end()) {
-    NOTREACHED();
-    return;
-  }
-  const PendingDecode& pending_decode = it->second;
-  host()->SendReply(
-      pending_decode.reply_context,
-      PpapiPluginMsg_VideoDecoder_DecodeReply(pending_decode.shm_id));
-  shm_buffer_busy_[pending_decode.shm_id] = false;
-  pending_decodes_.erase(it);
+  host()->SendUnsolicitedReply(
+      pp_resource(),
+      PpapiPluginMsg_VideoDecoder_RequestTextures(
+          requested_num_of_buffers,
+          PP_MakeSize(dimensions.width(), dimensions.height()),
+          texture_target,
+          mailboxes));
 }
 
-void PepperVideoDecoderHost::NotifyFlushDone() {
-  DCHECK(RenderThreadImpl::current());
-  host()->SendReply(flush_reply_context_,
-                    PpapiPluginMsg_VideoDecoder_FlushReply());
-  flush_reply_context_ = ppapi::host::ReplyMessageContext();
+void PepperVideoDecoderHost::NotifyError(int32_t pp_error) {
+  host()->SendUnsolicitedReply(
+      pp_resource(), PpapiPluginMsg_VideoDecoder_NotifyError(pp_error));
 }
 
 }  // namespace content
+
+namespace base {
+
+void DefaultDeleter<content::SoftwareDecoder>::operator()(
+    void* software_decoder) const {
+  static_cast<content::SoftwareDecoder*>(software_decoder)->Destroy();
+}
+
+}  // namespace base