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// Copyright 2018 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 <memory>
#include "chromecast/public/media/media_pipeline_backend.h"
#include "chromecast/public/media/media_pipeline_device_params.h"
namespace chromecast {
namespace media {
// This class represents a video decoder that exposes additional functionality
// that allows a caller to control the rate and state of the video playback
// with enough granularity to be able to sync it to the audio.
// The default implementation of this is in VideoDecoderNull. On no-video
// platforms, that implementation is used.
// On video platforms that need to use the mixer, you may override this class
// and link in an implementation of VideoDecoderForMixer::Create.
class VideoDecoderForMixer : public MediaPipelineBackend::VideoDecoder {
class Observer {
// Notifies the observer that the video playback is ready to start. After
// this is called, SetPts may be reliably called to start playback at the
// desired time.
virtual void VideoReadyToPlay() = 0;
virtual ~Observer() {}
static std::unique_ptr<VideoDecoderForMixer> Create(
const MediaPipelineDeviceParams& params);
// On some platforms, graphics needs to be initialized before this component
// will function appropriately in tests. Add the initialization here if
// necessary.
static void InitializeGraphicsForTesting();
~VideoDecoderForMixer() override {}
// Initializes the VideoDecoderForMixer. Called after allocation and before
// Start is called. Gives the implementation a chance to initialize any
// resources.
virtual bool Initialize() = 0;
// Sets the observer to be notified when the video is ready to play.
virtual void SetObserver(Observer* observer) = 0;
// When called, playback is expected to start from |start_pts|.
// start_pts: the pts to start playing at.
// need_avsync: deprecated. Don't use or implement.
// TODO(almasrymina): remove deprecated.
virtual bool Start(int64_t start_pts, bool need_avsync) = 0;
// Stop playback.
virtual void Stop() = 0;
// Pause playback. The video decoder must retain its playback rate after
// resume.
virtual bool Pause() = 0;
// Resume playback. The video decoder must resume playback at the same
// playback rate prior to pausing.
virtual bool Resume() = 0;
// Returns the current video PTS. This will typically be the pts of the last
// video frame displayed.
virtual bool GetCurrentPts(int64_t* timestamp, int64_t* pts) const = 0;
// Set the playback rate. This is used to sync the audio to the video. This
// call will change the rate of play of video in the following manner:
// rate = 1.0 -> 1 second of video pts is played for each 1 second of
// wallclock time.
// rate = 1.5 -> 1.5 seconds of video pts is played for each 1 second of
// wallclock time.
// etc.
virtual bool SetPlaybackRate(float rate) = 0;
// Sets the current pts to the provided value. If |pts| is greater than the
// current pts, all video frames in between will be dropped. If |pts| is less
// than the current pts, all video frames in this pts range will be repeated.
// Implementation is encouraged to smooth out this transition, such that
// minimal jitter in the video is shown, but that is not necessary.
virtual bool SetPts(int64_t timestamp, int64_t pts) = 0;
// Returns number of frames dropped since the last call to Start(). This is
// used to estimate video playback smoothness.
// This is different from VideoDecoder::Statistics::dropped_frames. That
// value is the number of *decoded* dropped frames. The value returned here
// must be the total number of dropped frames, whether the frames have been
// decoded or not.
virtual int64_t GetDroppedFrames() = 0;
// Returns number of frames repeated since the last call to Start(). This is
// used to estimate video playback smoothness. Note that repeated frames could
// be due to changes in the rate of playback, setting the PTS, or simply due
// to frame rate conversion. This number should be the sum of all of these
// factors.
// For example, if the current OutputRefreshRate is 60hz, and the current
// content frame rate is 24fps, it is expected to repeat 36fps.
virtual int64_t GetRepeatedFrames() = 0;
// Returns the output refresh rate on this platform, in mHz (millihertz). On
// display devices, this will be the display refresh rate. On HDMI devices,
// this will be the refresh rate of the HDMI connection.
virtual int64_t GetOutputRefreshRate() = 0;
// Returns the current content refresh rate in mHz (millihertz).
virtual int64_t GetCurrentContentRefreshRate() = 0;
} // namespace media
} // namespace chromecast