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// Copyright 2014 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.
#ifndef MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
#define MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
#include <utility>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
#include "base/synchronization/lock.h"
#include "base/time/tick_clock.h"
#include "base/timer/timer.h"
#include "cc/layers/video_frame_provider.h"
#include "media/base/video_renderer_sink.h"
#include "media/blink/media_blink_export.h"
#include "ui/gfx/geometry/size.h"
namespace media {
class VideoFrame;
// VideoFrameCompositor acts as a bridge between the media and cc layers for
// rendering video frames. I.e. a media::VideoRenderer will talk to this class
// from the media side, while a cc::VideoFrameProvider::Client will talk to it
// from the cc side.
//
// This class is responsible for requesting new frames from a video renderer in
// response to requests from the VFP::Client. Since the VFP::Client may stop
// issuing requests in response to visibility changes it is also responsible for
// ensuring the "freshness" of the current frame for programmatic frame
// requests; e.g., Canvas.drawImage() requests
//
// This class is also responsible for detecting frames dropped by the compositor
// after rendering and signaling that information to a RenderCallback. It
// detects frames not dropped by verifying each GetCurrentFrame() is followed
// by a PutCurrentFrame() before the next UpdateCurrentFrame() call.
//
// VideoRenderSink::RenderCallback implementations must call Start() and Stop()
// once new frames are expected or are no longer expected to be ready; this data
// is relayed to the compositor to avoid extraneous callbacks.
//
// VideoFrameCompositor is also responsible for pumping UpdateCurrentFrame()
// callbacks in the background when |client_| has decided to suspend them.
//
// VideoFrameCompositor must live on the same thread as the compositor, though
// it may be constructed on any thread.
class MEDIA_BLINK_EXPORT VideoFrameCompositor
: public VideoRendererSink,
NON_EXPORTED_BASE(public cc::VideoFrameProvider) {
public:
// |compositor_task_runner| is the task runner on which this class will live,
// though it may be constructed on any thread.
//
// |natural_size_changed_cb| is run with the new natural size of the video
// frame whenever a change in natural size is detected. Run on the same
// thread as the caller of UpdateCurrentFrame().
//
// |opacity_changed_cb| is run when a change in opacity is detected. It *is*
// called the first time UpdateCurrentFrame() is called. Run on the same
// thread as the caller of UpdateCurrentFrame().
VideoFrameCompositor(
const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner,
const base::Callback<void(gfx::Size)>& natural_size_changed_cb,
const base::Callback<void(bool)>& opacity_changed_cb);
// Destruction must happen on the compositor thread; Stop() must have been
// called before destruction starts.
~VideoFrameCompositor() override;
// cc::VideoFrameProvider implementation. These methods must be called on the
// |compositor_task_runner_|.
void SetVideoFrameProviderClient(
cc::VideoFrameProvider::Client* client) override;
bool UpdateCurrentFrame(base::TimeTicks deadline_min,
base::TimeTicks deadline_max) override;
bool HasCurrentFrame() override;
scoped_refptr<VideoFrame> GetCurrentFrame() override;
void PutCurrentFrame() override;
// VideoRendererSink implementation. These methods must be called from the
// same thread (typically the media thread).
void Start(RenderCallback* callback) override;
void Stop() override;
void PaintFrameUsingOldRenderingPath(
const scoped_refptr<VideoFrame>& frame) override;
// Returns |current_frame_| if |client_| is set. If no |client_| is set,
// |is_background_rendering_| is true, and |callback_| is set, it requests a
// new frame from |callback_|, using the elapsed time between calls to this
// function as the render interval; defaulting to 16.6ms if no prior calls
// have been made. A cap of 250Hz (4ms) is in place to prevent clients from
// accidentally (or intentionally) spamming the rendering pipeline.
//
// This method is primarily to facilitate canvas and WebGL based applications
// where the <video> tag is invisible (possibly not even in the DOM) and thus
// does not receive a |client_|. In this case, frame acquisition is driven by
// the frequency of canvas or WebGL paints requested via JavaScript.
scoped_refptr<VideoFrame> GetCurrentFrameAndUpdateIfStale();
// Returns the timestamp of the current (possibly stale) frame, or
// base::TimeDelta() if there is no current frame. This method may be called
// from the media thread as long as the VFC is stopped. (Assuming that
// PaintFrameUsingOldRenderingPath() is not also called while stopped.)
base::TimeDelta GetCurrentFrameTimestamp() const;
void set_tick_clock_for_testing(std::unique_ptr<base::TickClock> tick_clock) {
tick_clock_ = std::move(tick_clock);
}
void clear_current_frame_for_testing() { current_frame_ = nullptr; }
// Enables or disables background rendering. If |enabled|, |timeout| is the
// amount of time to wait after the last Render() call before starting the
// background rendering mode. Note, this can not disable the background
// rendering call issues when a sink is started.
void set_background_rendering_for_testing(bool enabled) {
background_rendering_enabled_ = enabled;
}
private:
// Called on the compositor thread in response to Start() or Stop() calls;
// must be used to change |rendering_| state.
void OnRendererStateUpdate(bool new_state);
// Handles setting of |current_frame_| and fires |natural_size_changed_cb_|
// and |opacity_changed_cb_| when the frame properties changes.
bool ProcessNewFrame(const scoped_refptr<VideoFrame>& frame);
// Called by |background_rendering_timer_| when enough time elapses where we
// haven't seen a Render() call.
void BackgroundRender();
// If |callback_| is available, calls Render() with the provided properties.
// Updates |is_background_rendering_|, |last_interval_|, and resets
// |background_rendering_timer_|. Ensures that natural size and opacity
// changes are correctly fired. Returns true if there's a new frame available
// via GetCurrentFrame().
bool CallRender(base::TimeTicks deadline_min,
base::TimeTicks deadline_max,
bool background_rendering);
scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
std::unique_ptr<base::TickClock> tick_clock_;
// These callbacks are executed on the compositor thread.
const base::Callback<void(gfx::Size)> natural_size_changed_cb_;
const base::Callback<void(bool)> opacity_changed_cb_;
// Allows tests to disable the background rendering task.
bool background_rendering_enabled_;
// Manages UpdateCurrentFrame() callbacks if |client_| has stopped sending
// them for various reasons. Runs on |compositor_task_runner_| and is reset
// after each successful UpdateCurrentFrame() call.
base::Timer background_rendering_timer_;
// These values are only set and read on the compositor thread.
cc::VideoFrameProvider::Client* client_;
bool rendering_;
bool rendered_last_frame_;
bool is_background_rendering_;
bool new_background_frame_;
base::TimeDelta last_interval_;
base::TimeTicks last_background_render_;
// These values are set on the compositor thread, but also read on the media
// thread when the VFC is stopped.
scoped_refptr<VideoFrame> current_frame_;
// These values are updated and read from the media and compositor threads.
base::Lock callback_lock_;
VideoRendererSink::RenderCallback* callback_;
DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
};
} // namespace media
#endif // MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_