Video Capture Pepper API

webkit/plugins/ppapi/ppb_video_capture_impl.cc

+// Copyright (c) 2011 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 "webkit/plugins/ppapi/ppb_video_capture_impl.h"
+
+#include <algorithm>
+#include <string>
+
+#include "base/logging.h"
+#include "ppapi/c/dev/pp_video_capture_dev.h"
+#include "ppapi/c/dev/ppb_video_capture_dev.h"
+#include "ppapi/c/pp_completion_callback.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/thunk/enter.h"
+#include "webkit/plugins/ppapi/common.h"
+#include "webkit/plugins/ppapi/plugin_module.h"
+#include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
+#include "webkit/plugins/ppapi/ppb_buffer_impl.h"
+#include "webkit/plugins/ppapi/resource_tracker.h"
+
+using ppapi::thunk::EnterResourceNoLock;
+using ppapi::thunk::PPB_Buffer_API;
+using ppapi::thunk::PPB_VideoCapture_API;
+
+namespace webkit {
+namespace ppapi {
+
+PPB_VideoCapture_Impl::PPB_VideoCapture_Impl(PluginInstance* instance)
+    : Resource(instance),
+      buffer_count_hint_(0),
+      status_(PP_VIDEO_CAPTURE_STATUS_STOPPED) {
+  ppp_videocapture_ =

[brettw, 2011/08/02 17:17:44]

I'd initialize this to null in the initializer list and then move this code to
the Init function, because that's where you're actually checking that it was
successfully retrieved.

[piman, 2011/08/03 00:44:41]

Done.

+      static_cast<const PPP_VideoCapture_Dev*>(instance->module()->
+          GetPluginInterface(PPP_VIDEO_CAPTURE_DEV_INTERFACE));
+}
+
+PPB_VideoCapture_Impl::~PPB_VideoCapture_Impl() {
+  if (platform_video_capture_.get())
+    StopCapture();
+}
+
+bool PPB_VideoCapture_Impl::Init() {
+  platform_video_capture_.reset(
+      instance()->delegate()->CreateVideoCapture(this));
+  return ppp_videocapture_ && platform_video_capture_.get();
+}
+
+PPB_VideoCapture_API* PPB_VideoCapture_Impl::AsPPB_VideoCapture_API() {
+  return this;
+}
+
+int32_t PPB_VideoCapture_Impl::StartCapture(
+    const PP_VideoCaptureDeviceInfo_Dev& requested_info,
+    uint32_t buffer_count) {
+  switch (status_) {
+    case PP_VIDEO_CAPTURE_STATUS_STARTING:
+    case PP_VIDEO_CAPTURE_STATUS_STARTED:
+    case PP_VIDEO_CAPTURE_STATUS_PAUSED:
+    default:
+      return PP_ERROR_FAILED;
+    case PP_VIDEO_CAPTURE_STATUS_STOPPED:
+    case PP_VIDEO_CAPTURE_STATUS_STOPPING:
+      break;
+  }
+  DCHECK(buffers_.empty());
+
+  buffer_count_hint_ = std::min(buffer_count, 1U);
+  media::VideoCapture::VideoCaptureCapability capability = {
+    requested_info.width,
+    requested_info.height,
+    requested_info.frames_per_second,
+    0,  // ignored.
+    media::VideoFrame::I420,
+    false,  // ignored
+    false  // resolution_fixed
+  };
+  status_ = PP_VIDEO_CAPTURE_STATUS_STARTING;
+  platform_video_capture_->StartCapture(this, capability);
+  return PP_OK;
+}
+
+int32_t PPB_VideoCapture_Impl::ReuseBuffer(uint32_t buffer) {
+  if (buffer >= buffers_.size() || !buffers_[buffer].in_use)
+    return PP_ERROR_BADARGUMENT;
+  buffers_[buffer].in_use = false;
+  return PP_OK;
+}
+
+int32_t PPB_VideoCapture_Impl::StopCapture() {
+  switch (status_) {
+    case PP_VIDEO_CAPTURE_STATUS_STOPPED:
+    case PP_VIDEO_CAPTURE_STATUS_STOPPING:
+    default:
+      return PP_ERROR_FAILED;

[wjia(left Chromium), 2011/08/02 16:22:28]

Is this a fatal error, or just warning? It might be ok for plugin to call
StopCapture more than once. IMO, it does no real harm, just like pressing "Esc"
key more than once in vi.

[piman, 2011/08/03 00:44:41]

It's essentially silent, except if the plugin looks at the result. So it's a
mechanism for the plugin writer to know that it's doing something wrong, but
without any other side effect.

+    case PP_VIDEO_CAPTURE_STATUS_STARTING:
+    case PP_VIDEO_CAPTURE_STATUS_STARTED:
+    case PP_VIDEO_CAPTURE_STATUS_PAUSED:
+      break;
+  }
+  FreeBuffers();
+  status_ = PP_VIDEO_CAPTURE_STATUS_STOPPING;
+  platform_video_capture_->StopCapture(this);
+  return PP_OK;
+}
+
+void PPB_VideoCapture_Impl::OnStarted(media::VideoCapture* capture) {
+  switch (status_) {
+    case PP_VIDEO_CAPTURE_STATUS_STARTING:
+    case PP_VIDEO_CAPTURE_STATUS_PAUSED:
+      break;
+    case PP_VIDEO_CAPTURE_STATUS_STOPPED:
+    case PP_VIDEO_CAPTURE_STATUS_STOPPING:
+    case PP_VIDEO_CAPTURE_STATUS_STARTED:
+    default:
+      return;
+  }
+  status_ = PP_VIDEO_CAPTURE_STATUS_STARTED;
+  SendStatus();
+}
+
+void PPB_VideoCapture_Impl::OnStopped(media::VideoCapture* capture) {
+  switch (status_) {
+    case PP_VIDEO_CAPTURE_STATUS_STOPPING:
+      break;
+    case PP_VIDEO_CAPTURE_STATUS_STARTING:
+    case PP_VIDEO_CAPTURE_STATUS_PAUSED:
+    case PP_VIDEO_CAPTURE_STATUS_STOPPED:
+    case PP_VIDEO_CAPTURE_STATUS_STARTED:
+    default:
+      return;
+  }
+  status_ = PP_VIDEO_CAPTURE_STATUS_STOPPED;
+  SendStatus();
+}
+
+void PPB_VideoCapture_Impl::OnPaused(media::VideoCapture* capture) {
+  switch (status_) {
+    case PP_VIDEO_CAPTURE_STATUS_STARTING:
+    case PP_VIDEO_CAPTURE_STATUS_STARTED:
+      break;
+    case PP_VIDEO_CAPTURE_STATUS_STOPPED:
+    case PP_VIDEO_CAPTURE_STATUS_STOPPING:
+    case PP_VIDEO_CAPTURE_STATUS_PAUSED:
+    default:
+      return;
+  }
+  status_ = PP_VIDEO_CAPTURE_STATUS_PAUSED;
+  SendStatus();
+}
+
+void PPB_VideoCapture_Impl::OnError(media::VideoCapture* capture,
+                                    int error_code) {
+  // Today, the media layer only sends "1" as an error.
+  DCHECK(error_code == 1);
+  // It either comes because some error was detected while starting (e.g. 2
+  // conflicting "master" resolution), or because the browser failed to start
+  // the capture.
+  status_ = PP_VIDEO_CAPTURE_STATUS_STOPPED;
+  ppp_videocapture_->OnError(instance()->pp_instance(),
+                             ScopedResourceId(this).id,
+                             PP_ERROR_FAILED);
+}
+
+void PPB_VideoCapture_Impl::OnBufferReady(
+    media::VideoCapture* capture,

[wjia(left Chromium), 2011/08/02 16:22:28]

This |capture| looks like an alien since PPB_VideoCapture_Impl doesn't know
anything about it. would it be good to check something (capture and
platform_video_capture_) since the buffer comes from |capture| and is returned
to platform_video_capture_? One way is to use platform_video_capture_ as
proxied_ in VideoCaptureProxy. 

[piman, 2011/08/03 00:44:41]

So, I was kinda wondering about that, but decided not to do anything special.
I can add logic to pass in the PlatformVideoCapture here (and other calls), but
since |capture| is not used at all in practice, then I figured I'd skip the
extra ~200 lines or so.

+    scoped_refptr<media::VideoCapture::VideoFrameBuffer> buffer) {

[wjia(left Chromium), 2011/08/02 16:22:28]

it would be good to check buffer (not a NULL pointer).

[piman, 2011/08/03 00:44:41]

Is there a reason the VideoCaptureImpl would send NULL ? I don't see how that'd
possible from the code.
Or are you just asking for a DCHECK (I added one) ?

[wjia(left Chromium), 2011/08/03 02:40:00]

I meant DCHECK which has been added.

+  if (!buffers_.empty()) {
+    for (uint32_t i = 0; i < buffers_.size(); ++i) {
+      if (!buffers_[i].in_use) {
+        // TODO(piman): it looks like stride isn't actually used/filled.
+        DCHECK(buffer->stride == 0);
+        size_t size = std::min(buffers_[i].buffer->size(), buffer->buffer_size);
+        memcpy(buffers_[i].data, buffer->memory_pointer, size);

[wjia(left Chromium), 2011/08/02 16:22:28]

would it be good to call "platform_video_capture_->FeedBuffer(buffer);" here to
return buffer faster to media layer? I hope plugin won't do some lengthy
processing in OnBufferReady.

[piman, 2011/08/03 00:44:41]

Done.

+        ppp_videocapture_->OnBufferReady(instance()->pp_instance(),
+            ScopedResourceId(this).id,
+            i);
+        break;
+      }
+    }
+  }
+  // TODO(piman): signal dropped buffers ?
+  platform_video_capture_->FeedBuffer(buffer);
+}
+
+void PPB_VideoCapture_Impl::OnDeviceInfoReceived(
+    media::VideoCapture* capture,
+    const media::VideoCaptureParams& device_info) {
+  PP_VideoCaptureDeviceInfo_Dev info = {
+    device_info.width,
+    device_info.height,
+    device_info.frame_per_second
+  };
+  FreeBuffers();

[wjia(left Chromium), 2011/08/02 16:22:28]

is it guaranteed that no buffer is in use by plugin at this time?

[piman, 2011/08/03 00:44:41]

The plugin is responsible for keeping its own references to the buffers.
FreeBuffers will simply release the browser-side references, so if the plugin
still has buffers in flight, it can keep them as long as it needs them, the
browser won't free them nor reuse them. When the plugin finally releases
references to its buffers, they will go away.
I renamed FreeBuffers into ReleaseBuffers to better describe the behavior.

+
+  // Allocate buffers. We keep a reference to them, that is released in
+  // FreeBuffers.
+  // YUV 4:2:0
+  int uv_width = info.width / 2;
+  int uv_height = info.height / 2;
+  size_t size = info.width * info.height + 2 * uv_width * uv_height;
+  scoped_array<PP_Resource> resources(new PP_Resource[buffer_count_hint_]);
+
+  buffers_.reserve(buffer_count_hint_);
+  for (size_t i = 0; i < buffer_count_hint_; ++i) {
+    resources[i] = PPB_Buffer_Impl::Create(instance(), size);
+    if (!resources[i]) {
+      break;
+    }
+
+    EnterResourceNoLock<PPB_Buffer_API> enter(resources[i], true);
+    DCHECK(enter.succeeded());
+
+    BufferInfo info;
+    info.buffer = static_cast<PPB_Buffer_Impl*>(enter.object());
+    info.data = info.buffer->Map();
+    if (!info.data) {
+      ResourceTracker::Get()->UnrefResource(resources[i]);
+      break;
+    }
+    buffers_.push_back(info);
+  }
+
+  if (buffers_.empty()) {
+    // We couldn't allocate/map buffers at all. Send an error and stop the
+    // capture.
+    ppp_videocapture_->OnError(instance()->pp_instance(),
+                               ScopedResourceId(this).id,
+                               PP_ERROR_NOMEMORY);
+    status_ = PP_VIDEO_CAPTURE_STATUS_STOPPING;
+    platform_video_capture_->StopCapture(this);
+    return;
+  }
+
+  ppp_videocapture_->OnDeviceInfo(instance()->pp_instance(),
+                                  ScopedResourceId(this).id,
+                                  &info,
+                                  buffers_.size(),
+                                  resources.get());
+}
+
+void PPB_VideoCapture_Impl::FreeBuffers() {
+  ResourceTracker *tracker = ResourceTracker::Get();
+  for (size_t i = 0; i < buffers_.size(); ++i) {
+    buffers_[i].buffer->Unmap();
+    tracker->UnrefResource(buffers_[i].buffer->GetReferenceNoAddRef());
+  }
+  buffers_.clear();
+}
+
+void PPB_VideoCapture_Impl::SendStatus() {
+  ppp_videocapture_->OnStatus(instance()->pp_instance(),
+                              ScopedResourceId(this).id,
+                              status_);
+}
+
+}  // namespace ppapi
+}  // namespace webkit