ppapi/cpp/media_stream_video_track.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
   6 #define PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
   7
   8 #include <string>
   9
  10 #include "ppapi/c/ppb_media_stream_video_track.h"
  11 #include "ppapi/cpp/resource.h"
  12 #include "ppapi/cpp/var.h"
  13
  14 /// @file
  15 /// This file defines the <code>MediaStreamVideoTrack</code> interface for a
  16 /// video source resource, which receives video frames from a MediaStream video
  17 /// track in the browser.
  18
  19 namespace pp {
  20
  21 class VideoFrame;
  22 class CompletionCallback;
  23 template <typename T> class CompletionCallbackWithOutput;
  24
  25 /// The <code>MediaStreamVideoTrack</code> class contains methods for
  26 /// receiving video frames from a MediaStream video track in the browser.
  27 class MediaStreamVideoTrack : public Resource {
  28  public:
  29   /// Default constructor for creating an is_null()
  30   /// <code>MediaStreamVideoTrack</code> object.
  31   MediaStreamVideoTrack();
  32
  33   /// The copy constructor for <code>MediaStreamVideoTrack</code>.
  34   ///
  35   /// @param[in] other A reference to a <code>MediaStreamVideoTrack</code>.
  36   MediaStreamVideoTrack(const MediaStreamVideoTrack& other);
  37
  38   /// Constructs a <code>MediaStreamVideoTrack</code> from
  39   /// a <code>Resource</code>.
  40   ///
  41   /// @param[in] resource A <code>PPB_MediaStreamVideoTrack</code> resource.
  42   explicit MediaStreamVideoTrack(const Resource& resource);
  43
  44   /// A constructor used when you have received a <code>PP_Resource</code> as a
  45   /// return value that has had 1 ref added for you.
  46   ///
  47   /// @param[in] resource A <code>PPB_MediaStreamVideoTrack</code> resource.
  48   MediaStreamVideoTrack(PassRef, PP_Resource resource);
  49
  50   ~MediaStreamVideoTrack();
  51
  52   /// Configures underlying frame buffers for incoming frames.
  53   /// If the application doesn't want to drop frames, then the
  54   /// <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES</code> should be
  55   /// chosen such that inter-frame processing time variability won't overrun the
  56   /// input buffer. If the buffer is overfilled, then frames will be dropped.
  57   /// The application can detect this by examining the timestamp on returned
  58   /// frames. If some attributes are not specified, default values will be used
  59   /// for those unspecified attributes. If <code>Configure()</code> is not
  60   /// called, default settings will be used.
  61   /// Example usage from plugin code:
  62   /// @code
  63   /// int32_t attribs[] = {
  64   ///     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES, 4,
  65   ///     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE};
  66   /// track.Configure(attribs, callback);
  67   /// @endcode
  68   ///
  69   /// @param[in] attrib_list A list of attribute name-value pairs in which each
  70   /// attribute is immediately followed by the corresponding desired value.
  71   /// The list is terminated by
  72   /// <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE</code>.
  73   /// @param[in] callback A <code>CompletionCallback</code> to be called upon
  74   /// completion of <code>Configure()</code>.
  75   ///
  76   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
  77   /// Returns <code>PP_ERROR_INPROGRESS</code> if there is a pending call of
  78   /// <code>Configure()</code> or <code>GetFrame()</code>, or the plugin
  79   /// holds some frames which are not recycled with <code>RecycleFrame()</code>.
  80   /// If an error is returned, all attributes and the underlying buffer will not
  81   /// be changed.
  82   int32_t Configure(const int32_t attributes[],
  83                     const CompletionCallback& callback);
  84
  85   /// Gets attribute value for a given attribute name.
  86   ///
  87   /// @param[in] attrib A <code>PP_MediaStreamVideoTrack_Attrib</code> for
  88   /// querying.
  89   /// @param[out] value A int32_t for storing the attribute value.
  90   ///
  91   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
  92   int32_t GetAttrib(PP_MediaStreamVideoTrack_Attrib attrib,
  93                     int32_t* value);
  94
  95   /// Returns the track ID of the underlying MediaStream video track.
  96   std::string GetId() const;
  97
  98   /// Checks whether the underlying MediaStream track has ended.
  99   /// Calls to GetFrame while the track has ended are safe to make and will
 100   /// complete, but will fail.
 101   bool HasEnded() const;
 102
 103   /// Gets the next video frame from the MediaStream track.
 104   /// If internal processing is slower than the incoming frame rate, new frames
 105   /// will be dropped from the incoming stream. Once the input buffer is full,
 106   /// frames will be dropped until <code>RecycleFrame()</code> is called to free
 107   /// a spot for another frame to be buffered.
 108   /// If there are no frames in the input buffer,
 109   /// <code>PP_OK_COMPLETIONPENDING</code> will be returned immediately and the
 110   /// <code>callback</code> will be called when a new frame is received or some
 111   /// error happens.
 112   ///
 113   /// @param[in] callback A <code>CompletionCallbackWithOutput</code> to be
 114   /// called upon completion of <code>GetFrame()</code>. If success,
 115   /// a VideoFrame will be passed into the completion callback function.
 116   ///
 117   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
 118   /// Returns PP_ERROR_NOMEMORY if <code>max_buffered_frames</code> frames
 119   /// buffer was not allocated successfully.
 120   int32_t GetFrame(
 121       const CompletionCallbackWithOutput<VideoFrame>& callback);
 122
 123   /// Recycles a frame returned by <code>GetFrame()</code>, so the track can
 124   /// reuse the underlying buffer of this frame. And the frame will become
 125   /// invalid. The caller should release all references it holds to
 126   /// <code>frame</code> and not use it anymore.
 127   ///
 128   /// @param[in] frame A VideoFrame returned by <code>GetFrame()</code>.
 129   ///
 130   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
 131   int32_t RecycleFrame(const VideoFrame& frame);
 132
 133   /// Closes the MediaStream video track, and disconnects it from video source.
 134   /// After calling <code>Close()</code>, no new frames will be received.
 135   void Close();
 136
 137   /// Checks whether a <code>Resource</code> is a MediaStream video track,
 138   /// to test whether it is appropriate for use with the
 139   /// <code>MediaStreamVideoTrack</code> constructor.
 140   ///
 141   /// @param[in] resource A <code>Resource</code> to test.
 142   ///
 143   /// @return True if <code>resource</code> is a MediaStream video track.
 144   static bool IsMediaStreamVideoTrack(const Resource& resource);
 145 };
 146
 147 }  // namespace pp
 148
 149 #endif  // PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_