Effects Pepper Plugin and MediaStream Glue.

content/renderer/media/video_destination_handler.cc

+// 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/video_destination_handler.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "content/renderer/media/media_stream_dependency_factory.h"
+#include "content/renderer/media/media_stream_registry_interface.h"
+#include "content/renderer/render_thread_impl.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebMediaStreamRegistry.h"
+
+using cricket::CaptureState;
+using cricket::VideoFormat;
+
+static const cricket::FourCC kEffectColorFormat = cricket::FOURCC_BGRA;
+
+namespace content {
+
+PpFrameWriter::PpFrameWriter()
+    : started_(false) {}
+
+PpFrameWriter::~PpFrameWriter() {}
+
+CaptureState PpFrameWriter::Start(const VideoFormat& capture_format) {
+  if (started_) {
+    LOG(ERROR) << "PpFrameWriter::Start - "
+               << "Got a StartCapture when already started!";
+    return cricket::CS_FAILED;
+  }
+  started_ = true;
+  return cricket::CS_STARTING;
+}
+
+void PpFrameWriter::Stop() {
+  started_ = false;
+  SignalStateChange(this, cricket::CS_STOPPED);
+}
+
+bool PpFrameWriter::IsRunning() {
+  return started_;
+}
+
+bool PpFrameWriter::GetPreferredFourccs(std::vector<uint32>* fourccs) {
+  if (!fourccs) {
+    LOG(ERROR) << "PpFrameWriter::GetPreferredFourccs - "
+               << "fourccs is NULL.";
+    return false;
+  }
+  // The effects plugin output BGRA.
+  fourccs->push_back(kEffectColorFormat);
+  return true;
+}
+
+bool PpFrameWriter::GetBestCaptureFormat(const VideoFormat& desired,
+                                         VideoFormat* best_format) {
+  if (!best_format) {
+    LOG(ERROR) << "PpFrameWriter::GetBestCaptureFormat - "
+               << "best_format is NULL.";
+    return false;
+    return false;
+  }
+
+  // Use the desired format as the best format.
+  // TODO(ronghuawu): How to handle this better?
+  best_format->width = desired.width;
+  best_format->height = desired.height;
+  best_format->fourcc = kEffectColorFormat;
+  best_format->interval = desired.interval;
+  return true;
+}
+
+bool PpFrameWriter::IsScreencast() const {
+  return false;
+}
+
+void PpFrameWriter::PutFrame(cricket::CapturedFrame* frame) {
+  if (!started_) {

[wjia(left Chromium), 2013/04/30 18:32:11]

Is there race condition to access |started_|? AFAIK, PutFrame will be called on
render thread since it comes from Pepper. On which thread Stop() will be called?

[Ronghua Wu (Left Chromium), 2013/04/30 22:42:17]

Stop will be called from a libjingle worker thread. So there's a race condition.
What about just remove the check?

+    LOG(ERROR) << "Got a PutFrame when the capturer is not started!";
+    return;
+  }
+
+  // This signals to libJingle that a new VideoFrame is available.
+  // libJingle have no assumptions on what thread this signal come from.
+  SignalFrameCaptured(this, frame);
+}
+
+VideoDestinationHandler::VideoDestinationHandler(
+    MediaStreamDependencyFactory* factory,
+    MediaStreamRegistryInterface* registry)

[wjia(left Chromium), 2013/04/30 18:32:11]

What's the life time of factory and registry? How to prevent use-after-free?

[Ronghua Wu (Left Chromium), 2013/04/30 22:42:17]

VideoDestinationHandler, the factory and the registry are all owned by the user
of VideoDestinationHandler - in our case the pepper plugin host. So I expect the
pepper plugin host will take care of the life time.

+    : factory_(factory),
+      registry_(registry) {
+  ASSERT(factory_ != NULL);
+}
+
+bool VideoDestinationHandler::Open(
+    const std::string& url, FrameWriterInterface** frame_writer) {
+  WebKit::WebMediaStream stream;
+  if (registry_) {
+    stream = registry_->GetMediaStream(url);
+  } else {
+    stream =
+        WebKit::WebMediaStreamRegistry::lookupMediaStreamDescriptor(GURL(url));
+  }
+  if (stream.isNull() || !stream.extraData()) {
+    LOG(ERROR) << "VideoDestinationHandler::Open - invalid url: " << url;
+    return false;
+  }
+
+  // Create a new native video track and add it to |stream|.
+  std::string track_id = talk_base::ToString(talk_base::CreateRandomId64());
+  PpFrameWriter* capturer = new PpFrameWriter();

[wjia(left Chromium), 2013/04/30 18:32:11]

Does it make sense to make PpFrameWriter class internal to this file if it won't
be accessed directly from outside?

[Ronghua Wu (Left Chromium), 2013/04/30 22:42:17]

It makes sense. But also what to have unit tests for it. It won't be possible if
I put it inside the cc file.

+  if (!factory_->AddNativeVideoMediaTrack(track_id, &stream, capturer)) {
+    delete capturer;
+    return false;
+  }
+
+  *frame_writer = capturer;
+  return true;
+}
+
+VideoDestinationHandler::~VideoDestinationHandler() {
+}
+
+}  // namespace content
+