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   /// Constructs a <code>MediaStreamVideoTrack</code> that outputs given frames
  45   /// to a new video track, which will be consumed by Javascript.
  46   explicit MediaStreamVideoTrack(const InstanceHandle& instance);
  47
  48   /// A constructor used when you have received a <code>PP_Resource</code> as a
  49   /// return value that has had 1 ref added for you.
  50   ///
  51   /// @param[in] resource A <code>PPB_MediaStreamVideoTrack</code> resource.
  52   MediaStreamVideoTrack(PassRef, PP_Resource resource);
  53
  54   ~MediaStreamVideoTrack();
  55
  56   /// Configures underlying frame buffers for incoming frames.
  57   /// If the application doesn't want to drop frames, then the
  58   /// <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES</code> should be
  59   /// chosen such that inter-frame processing time variability won't overrun the
  60   /// input buffer. If the buffer is overfilled, then frames will be dropped.
  61   /// The application can detect this by examining the timestamp on returned
  62   /// frames. If some attributes are not specified, default values will be used
  63   /// for those unspecified attributes. If <code>Configure()</code> is not
  64   /// called, default settings will be used.
  65   /// Example usage from plugin code:
  66   /// @code
  67   /// int32_t attribs[] = {
  68   ///     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES, 4,
  69   ///     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE};
  70   /// track.Configure(attribs, callback);
  71   /// @endcode
  72   ///
  73   /// @param[in] attrib_list A list of attribute name-value pairs in which each
  74   /// attribute is immediately followed by the corresponding desired value.
  75   /// The list is terminated by
  76   /// <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE</code>.
  77   /// @param[in] callback A <code>CompletionCallback</code> to be called upon
  78   /// completion of <code>Configure()</code>.
  79   ///
  80   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
  81   /// Returns <code>PP_ERROR_INPROGRESS</code> if there is a pending call of
  82   /// <code>Configure()</code> or <code>GetFrame()</code>, or the plugin
  83   /// holds some frames which are not recycled with <code>RecycleFrame()</code>.
  84   /// If an error is returned, all attributes and the underlying buffer will not
  85   /// be changed.
  86   int32_t Configure(const int32_t attributes[],
  87                     const CompletionCallback& callback);
  88
  89   /// Gets attribute value for a given attribute name.
  90   ///
  91   /// @param[in] attrib A <code>PP_MediaStreamVideoTrack_Attrib</code> for
  92   /// querying.
  93   /// @param[out] value A int32_t for storing the attribute value.
  94   ///
  95   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
  96   int32_t GetAttrib(PP_MediaStreamVideoTrack_Attrib attrib,
  97                     int32_t* value);
  98
  99   /// Returns the track ID of the underlying MediaStream video track.
 100   std::string GetId() const;
 101
 102   /// Checks whether the underlying MediaStream track has ended.
 103   /// Calls to GetFrame while the track has ended are safe to make and will
 104   /// complete, but will fail.
 105   bool HasEnded() const;
 106
 107   /// Gets the next video frame from the MediaStream track.
 108   /// If internal processing is slower than the incoming frame rate, new frames
 109   /// will be dropped from the incoming stream. Once the input buffer is full,
 110   /// frames will be dropped until <code>RecycleFrame()</code> is called to free
 111   /// a spot for another frame to be buffered.
 112   /// If there are no frames in the input buffer,
 113   /// <code>PP_OK_COMPLETIONPENDING</code> will be returned immediately and the
 114   /// <code>callback</code> will be called when a new frame is received or some
 115   /// error happens.
 116   ///
 117   /// @param[in] callback A <code>CompletionCallbackWithOutput</code> to be
 118   /// called upon completion of <code>GetFrame()</code>. If success,
 119   /// a VideoFrame will be passed into the completion callback function.
 120   ///
 121   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
 122   /// Returns PP_ERROR_NOMEMORY if <code>max_buffered_frames</code> frames
 123   /// buffer was not allocated successfully.
 124   int32_t GetFrame(
 125       const CompletionCallbackWithOutput<VideoFrame>& callback);
 126
 127   /// Recycles a frame returned by <code>GetFrame()</code>, so the track can
 128   /// reuse the underlying buffer of this frame. And the frame will become
 129   /// invalid. The caller should release all references it holds to
 130   /// <code>frame</code> and not use it anymore.
 131   ///
 132   /// @param[in] frame A VideoFrame returned by <code>GetFrame()</code>.
 133   ///
 134   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
 135   int32_t RecycleFrame(const VideoFrame& frame);
 136
 137   /// Closes the MediaStream video track, and disconnects it from video source.
 138   /// After calling <code>Close()</code>, no new frames will be received.
 139   void Close();
 140
 141   // Gets a free frame for output. The frame is allocated by
 142   // <code>Configure()</code>. The caller should fill it with frame data, and
 143   // then use |PutFrame()| to send the frame back.
 144   int32_t GetEmptyFrame(
 145       const CompletionCallbackWithOutput<VideoFrame>& callback);
 146
 147   // Sends a frame returned by |GetEmptyFrame()| to the output track.
 148   // After this function, the |frame| should not be used anymore and the
 149   // caller should release the reference that it holds.
 150   int32_t PutFrame(const VideoFrame& frame);
 151
 152   /// Checks whether a <code>Resource</code> is a MediaStream video track,
 153   /// to test whether it is appropriate for use with the
 154   /// <code>MediaStreamVideoTrack</code> constructor.
 155   ///
 156   /// @param[in] resource A <code>Resource</code> to test.
 157   ///
 158   /// @return True if <code>resource</code> is a MediaStream video track.
 159   static bool IsMediaStreamVideoTrack(const Resource& resource);
 160 };
 161
 162 }  // namespace pp
 163
 164 #endif  // PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_