src/media/base/shell_media_platform.h

/*
 * Copyright 2012 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef MEDIA_BASE_SHELL_MEDIA_PLATFORM_H_
#define MEDIA_BASE_SHELL_MEDIA_PLATFORM_H_

#include "base/basictypes.h"
#include "base/logging.h"
#include "base/memory/ref_counted.h"
#include "media/base/decoder_buffer.h"
#include "media/base/limits.h"
#include "media/base/media_export.h"
#include "media/base/shell_buffer_factory.h"
#include "media/base/shell_video_data_allocator.h"
#include "media/base/shell_video_frame_provider.h"

namespace media {

// This class is meant to be the single point to attach platform specific media
// classes and settings. Each platform should implement its own implementation
// and provide it through ShellMediaPlatform::Instance.
class MEDIA_EXPORT ShellMediaPlatform {
 public:
  ShellMediaPlatform() {}
  virtual ~ShellMediaPlatform() {}

  // Individual platforms should implement the following two functions to
  // ensure that a valid ShellMediaPlatform instance is available during the
  // life time of media stack
  static void Initialize();
  static void Terminate();

  static ShellMediaPlatform* Instance();

  // Media stack buffer allocate/free functions currently only used by
  // ShellBufferFactory.
  virtual void* AllocateBuffer(size_t size) = 0;
  virtual void FreeBuffer(void* ptr) = 0;

  // The maximum audio and video buffer size used by SourceBufferStream.
  // See implementation of SourceBufferStream for more details.
  virtual size_t GetSourceBufferStreamAudioMemoryLimit() const = 0;
  virtual size_t GetSourceBufferStreamVideoMemoryLimit() const = 0;

  virtual scoped_refptr<ShellVideoFrameProvider> GetVideoFrameProvider() {
    return NULL;
  }

  // Total number of video frames which are populating in the pipeline when
  // prerolling.
  // You can expect more start delay by increasing this.
  virtual int GetMaxVideoPrerollFrames() const {
    return limits::kMaxVideoFrames;
  }
  // When the video frame backlog contains less frames than this value, the
  // video renderer will send out underflow notification to the video decoder.
  virtual int GetVideoUnderflowFrames() const {
    return GetMaxVideoPrerollFrames();
  }
  // Total number of video frames which are populating in the pipeline.
  // You can expect more memory usage and less jitter by increasing this.
  virtual int GetMaxVideoFrames() const { return limits::kMaxVideoFrames; }

  // This function is called before the decoder buffer leaves the demuxer and
  // is being sent to the media pipeline for decrypting and decoding. The
  // default implementation simply returns the buffer indicateing that there is
  // no processing necessary.
  virtual scoped_refptr<DecoderBuffer> ProcessBeforeLeavingDemuxer(
      const scoped_refptr<DecoderBuffer>& buffer) {
    return buffer;
  }

  // Returns true if output is protected (i.e. HDCP is present).
  virtual bool IsOutputProtected() = 0;

 protected:
  static void SetInstance(ShellMediaPlatform* shell_media_platform);

 private:
  // Platform specific media Init and Tear down.
  virtual void InternalInitialize() {}
  virtual void InternalTerminate() {}

  DISALLOW_COPY_AND_ASSIGN(ShellMediaPlatform);
};

}  // namespace media

#define REGISTER_SHELL_MEDIA_PLATFORM(ClassName) \
  namespace media {                              \
  void ShellMediaPlatform::Initialize() {        \
    DCHECK(!Instance());                         \
    SetInstance(new ClassName);                  \
    ShellBufferFactory::Initialize();            \
    Instance()->InternalInitialize();            \
  }                                              \
  void ShellMediaPlatform::Terminate() {         \
    DCHECK(Instance());                          \
    Instance()->InternalTerminate();             \
    ShellBufferFactory::Terminate();             \
    delete Instance();                           \
    SetInstance(NULL);                           \
  }                                              \
  }  // namespace media

#endif  // MEDIA_BASE_SHELL_MEDIA_PLATFORM_H_