media/base/renderer.h

// 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_BASE_RENDERER_H_
#define MEDIA_BASE_RENDERER_H_

#include <vector>

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "media/base/buffering_state.h"
#include "media/base/cdm_context.h"
#include "media/base/media_export.h"
#include "media/base/pipeline_status.h"

namespace media {

class DemuxerStream;
class DemuxerStreamProvider;
class VideoFrame;

class MEDIA_EXPORT Renderer {
 public:
  Renderer();

  // Stops rendering and fires any pending callbacks.
  virtual ~Renderer();

  // Initializes the Renderer with |demuxer_stream_provider|, executing
  // |init_cb| upon completion.  If initialization fails, only |init_cb| (not
  // |error_cb|) should be called.  |demuxer_stream_provider| must be valid for
  // the lifetime of the Renderer object.  |init_cb| must only be run after this
  // method has returned.  Firing |init_cb| may result in the immediate
  // destruction of the caller, so it must be run only prior to returning.
  //
  // Permanent callbacks:
  // - |statistics_cb|: Executed periodically with rendering statistics.
  // - |buffering_state_cb|: Executed when buffering state is changed.
  // - |ended_cb|: Executed when rendering has reached the end of stream.
  // - |error_cb|: Executed if any error was encountered after initialization.
  // - |waiting_for_decryption_key_cb|: Executed whenever the key needed to
  //                                    decrypt the stream is not available.
  virtual void Initialize(
      DemuxerStreamProvider* demuxer_stream_provider,
      const PipelineStatusCB& init_cb,
      const StatisticsCB& statistics_cb,
      const BufferingStateCB& buffering_state_cb,
      const base::Closure& ended_cb,
      const PipelineStatusCB& error_cb,
      const base::Closure& waiting_for_decryption_key_cb) = 0;

  // Associates the |cdm_context| with this Renderer for decryption (and
  // decoding) of media data, then fires |cdm_attached_cb| with the result.
  virtual void SetCdm(CdmContext* cdm_context,
                      const CdmAttachedCB& cdm_attached_cb) = 0;

  // The following functions must be called after Initialize().

  // Discards any buffered data, executing |flush_cb| when completed.
  virtual void Flush(const base::Closure& flush_cb) = 0;

  // Starts rendering from |time|.
  virtual void StartPlayingFrom(base::TimeDelta time) = 0;

  // Updates the current playback rate. The default playback rate should be 1.
  virtual void SetPlaybackRate(double playback_rate) = 0;

  // Sets the output volume. The default volume should be 1.
  virtual void SetVolume(float volume) = 0;

  // Returns the current media time.
  virtual base::TimeDelta GetMediaTime() = 0;

  // Returns whether |this| renders audio.
  virtual bool HasAudio() = 0;

  // Returns whether |this| renders video.
  virtual bool HasVideo() = 0;

  // TODO(servolk,wolenetz): Enable media track handling in mojo, then make sure
  // OnEnabledAudioStreamsChanged and OnSelectedVideoStreamChanged are
  // implemented by all media renderers and make them pure virtual here.
  // crbug.com/604083

  // Notifies renderer that the set of enabled audio streams/tracks has changed.
  // The input parameter |enabledAudioStreams| might be empty, which means that
  // all audio tracks should be disabled/muted.
  virtual void OnEnabledAudioStreamsChanged(
      const std::vector<const DemuxerStream*>& enabledAudioStreams) {}

  // Notifies renderer that the selected video stream has changed. The input
  // parameter |selectedVideoStream| can be null, which means video is disabled.
  virtual void OnSelectedVideoStreamChanged(
      const DemuxerStream* selectedVideoStream) {}

 private:
  DISALLOW_COPY_AND_ASSIGN(Renderer);
};

}  // namespace media

#endif  // MEDIA_BASE_RENDERER_H_