path: root/media/base/filters.h

// Copyright (c) 2006-2009 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.

// Filters are connected in a strongly typed manner, with downstream filters
// always reading data from upstream filters.  Upstream filters have no clue
// who is actually reading from them, and return the results via callbacks.
//
//                         DemuxerStream(Video) <- VideoDecoder <- VideoRenderer
// DataSource <- Demuxer <
//                         DemuxerStream(Audio) <- AudioDecoder <- AudioRenderer
//
// Upstream -------------------------------------------------------> Downstream
//                         <- Reads flow this way
//                    Buffer assignments flow this way ->
//
// Every filter maintains a reference to the scheduler, who maintains data
// shared between filters (i.e., reference clock value, playback state).  The
// scheduler is also responsible for scheduling filter tasks (i.e., a read on
// a VideoDecoder would result in scheduling a Decode task).  Filters can also
// use the scheduler to signal errors and shutdown playback.

#ifndef MEDIA_BASE_FILTERS_H_
#define MEDIA_BASE_FILTERS_H_

#include <limits>
#include <string>

#include "base/logging.h"
#include "base/message_loop.h"
#include "base/ref_counted.h"
#include "base/time.h"
#include "media/base/media_format.h"

namespace media {

class Buffer;
class Decoder;
class DemuxerStream;
class FilterHost;
class VideoFrame;
class WritableBuffer;

// Identifies the type of filter implementation.  Used in conjunction with some
// template wizardry to enforce strongly typed operations.  More or less a
// knock off of MSVC's __uuidof() operator.
enum FilterType {
  FILTER_DATA_SOURCE,
  FILTER_DEMUXER,
  FILTER_AUDIO_DECODER,
  FILTER_VIDEO_DECODER,
  FILTER_AUDIO_RENDERER,
  FILTER_VIDEO_RENDERER
};


class MediaFilter : public base::RefCountedThreadSafe<MediaFilter> {
 public:
  MediaFilter() : host_(NULL), message_loop_(NULL) {}

  // Sets the protected member |host_|. This is the first method called by
  // the FilterHost after a filter is created.  The host holds a strong
  // reference to the filter.  The reference held by the host is guaranteed
  // to be released before the host object is destroyed by the pipeline.
  virtual void SetFilterHost(FilterHost* host) {
    DCHECK(host);
    DCHECK(!host_);
    host_ = host;
  }

  // Sets the protected member |message_loop_|, which is used by filters for
  // processing asynchronous tasks and maintaining synchronized access to
  // internal data members.  The message loop should be running and exceed the
  // lifetime of the filter.
  virtual void SetMessageLoop(MessageLoop* message_loop) {
    DCHECK(message_loop);
    DCHECK(!message_loop_);
    message_loop_ = message_loop;
  }

  // The pipeline is being stopped either as a result of an error or because
  // the client called Stop().
  virtual void Stop() = 0;

  // The pipeline playback rate has been changed.  Filters may implement this
  // method if they need to respond to this call.
  virtual void SetPlaybackRate(float playback_rate) {}

  // The pipeline is seeking to the specified time.  Filters may implement
  // this method if they need to respond to this call.
  virtual void Seek(base::TimeDelta time) {}

 protected:
  // Only allow scoped_refptr<> to delete filters.
  friend class base::RefCountedThreadSafe<MediaFilter>;
  virtual ~MediaFilter() {}

  // TODO(scherkus): make these private with public/protected accessors.
  FilterHost* host_;
  MessageLoop* message_loop_;

 private:
  DISALLOW_COPY_AND_ASSIGN(MediaFilter);
};


class DataSource : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_DATA_SOURCE;
  }

  static bool IsMediaFormatSupported(const MediaFormat& media_format) {
    std::string mime_type;
    return (media_format.GetAsString(MediaFormat::kMimeType, &mime_type) &&
            mime_type == mime_type::kURL);
  }

  static const size_t kReadError = static_cast<size_t>(-1);

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(const std::string& url) = 0;

  // Returns the MediaFormat for this filter.
  virtual const MediaFormat& media_format() = 0;

  // Read the given amount of bytes into data, returns the number of bytes read
  // if successful, kReadError otherwise.
  virtual size_t Read(uint8* data, size_t size) = 0;

  // Returns true and the current file position for this file, false if the
  // file position could not be retrieved.
  virtual bool GetPosition(int64* position_out) = 0;

  // Returns true if the file position could be set, false otherwise.
  virtual bool SetPosition(int64 position) = 0;

  // Returns true and the file size, false if the file size could not be
  // retrieved.
  virtual bool GetSize(int64* size_out) = 0;

  // Returns true if this data source supports random seeking.
  virtual bool IsSeekable() = 0;
};


class Demuxer : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_DEMUXER;
  }

  static bool IsMediaFormatSupported(const MediaFormat& media_format) {
    std::string mime_type;
    return (media_format.GetAsString(MediaFormat::kMimeType, &mime_type) &&
            mime_type == mime_type::kApplicationOctetStream);
  }

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(DataSource* data_source) = 0;

  // Returns the number of streams available
  virtual size_t GetNumberOfStreams() = 0;

  // Returns the stream for the given index, NULL otherwise
  virtual scoped_refptr<DemuxerStream> GetStream(int stream_id) = 0;
};


class DemuxerStream : public base::RefCountedThreadSafe<DemuxerStream> {
 public:
  // Returns the MediaFormat for this filter.
  virtual const MediaFormat& media_format() = 0;

  // Schedules a read.  When the |read_callback| is called, the downstream
  // filter takes ownership of the buffer by AddRef()'ing the buffer.
  //
  // TODO(scherkus): switch Read() callback to scoped_refptr<>.
  virtual void Read(Callback1<Buffer*>::Type* read_callback) = 0;

  // Given a class that supports the |Interface| and a related static method
  // interface_id(), which returns a const char*, this method returns true if
  // the class returns an interface pointer and assigns the pointer to
  // |interface_out|.  Otherwise this method returns false.
  template <class Interface>
  bool QueryInterface(Interface** interface_out) {
    void* i = QueryInterface(Interface::interface_id());
    *interface_out = reinterpret_cast<Interface*>(i);
    return (NULL != i);
  };

 protected:
  // Optional method that is implemented by filters that support extended
  // interfaces.  The filter should return a pointer to the interface
  // associated with the |interface_id| string if they support it, otherwise
  // return NULL to indicate the interface is unknown.  The derived filter
  // should NOT AddRef() the interface.  The DemuxerStream::QueryInterface()
  // public template function will assign the interface to a scoped_refptr<>.
  virtual void* QueryInterface(const char* interface_id) { return NULL; }

  friend class base::RefCountedThreadSafe<DemuxerStream>;
  virtual ~DemuxerStream() {}
};


class VideoDecoder : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_VIDEO_DECODER;
  }

  static const char* major_mime_type() {
    return mime_type::kMajorTypeVideo;
  }

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(DemuxerStream* demuxer_stream) = 0;

  // Returns the MediaFormat for this filter.
  virtual const MediaFormat& media_format() = 0;

  // Schedules a read.  Decoder takes ownership of the callback.
  //
  // TODO(scherkus): switch Read() callback to scoped_refptr<>.
  virtual void Read(Callback1<VideoFrame*>::Type* read_callback) = 0;
};


class AudioDecoder : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_AUDIO_DECODER;
  }

  static const char* major_mime_type() {
    return mime_type::kMajorTypeAudio;
  }

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(DemuxerStream* demuxer_stream) = 0;

  // Returns the MediaFormat for this filter.
  virtual const MediaFormat& media_format() = 0;

  // Schedules a read.  Decoder takes ownership of the callback.
  //
  // TODO(scherkus): switch Read() callback to scoped_refptr<>.
  virtual void Read(Callback1<Buffer*>::Type* read_callback) = 0;
};


class VideoRenderer : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_VIDEO_RENDERER;
  }

  static const char* major_mime_type() {
    return mime_type::kMajorTypeVideo;
  }

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(VideoDecoder* decoder) = 0;
};


class AudioRenderer : public MediaFilter {
 public:
  static const FilterType filter_type() {
    return FILTER_AUDIO_RENDERER;
  }

  static const char* major_mime_type() {
    return mime_type::kMajorTypeAudio;
  }

  // Initializes this filter, returns true if successful, false otherwise.
  virtual bool Initialize(AudioDecoder* decoder) = 0;

  // Sets the output volume.
  virtual void SetVolume(float volume) = 0;
};

}  // namespace media

#endif  // MEDIA_BASE_FILTERS_H_