[PPAPI] API definition for video media stream artifacts

ppapi/cpp/media_stream_video_track.h

+// Copyright (c) 2013 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 PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
+#define PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
+
+#include <string>
+
+#include "ppapi/c/pp_stdint.h"
+#include "ppapi/cpp/resource.h"
+
+/// @file
+/// This file defines the <code>MediaStreamVideoTrack</code> interface for a
+/// video source resource, which receives video frames from a MediaStream video
+/// track in the browser.
+
+namespace pp {
+
+class VideoFrame;
+template <typename T> class CompletionCallbackWithOutput;
+
+/// The <code>MediaStreamVideoTrack</code> class contains methods for
+/// receiving video frames from a MediaStream video track in the browser.
+class MediaStreamVideoTrack : public Resource {
+ public:
+  /// Default constructor for creating an is_null()
+  /// <code>MediaStreamVideoTrack</code> object.
+  MediaStreamVideoTrack();
+
+  /// A constructor used when you have received a <code>PP_Resource</code> as a
+  /// return value that has had 1 ref added for you.
+  ///
+  /// @param[in] resource A <code>PPB_MediaStreamVideoTrack</code> resource.
+  MediaStreamVideoTrack(PassRef, PP_Resource resource);
+
+  ~MediaStreamVideoTrack();
+
+  /// Configures underlaying frame buffers for incoming frames.
+  /// If the application doesn't want to drop frames, then the
+  /// |max_buffered_frames| should be chosen such that inter-frame
+  /// processing time variability won't overrun the input buffer. If the buffer
+  /// is overfilled, then frames will be dropped. The application can detect
+  /// this by examining the timestamp on returned frames. If |Configure()| is
+  /// not used, default settings will be used.
+  ///
+  /// @param[in] max_buffered_frames The maximum number of video frames to
+  /// hold in input buffer.
+  ///
+  /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
+  int32_t Configure(uint32_t max_buffered_frames);
+
+  /// Returns the track ID of the underlying MediaStream video track.
+  std::string GetId() const;
+
+  /// Checks whether the underlying MediaStream track has ended.
+  /// Calls to GetFrame while the track has ended are safe to make and will
+  /// complete, but will fail.
+  bool HasEnded() const;
+
+  /// Gets the next video frame from the MediaStream track.
+  /// If internal processing is slower than the incoming frame rate, new frames
+  /// will be dropped from the incoming stream. Once the input buffer is full,
+  /// frames will be dropped until |RecycleFrame()| is called to free a spot for
+  /// another frame to be buffered. If the caller holds a frame returned by
+  /// the previous call of |GetFrame()|, <code>PP_ERROR_INGROGRESS</code> will
+  /// be returned. The caller should recycle the previous frame, before getting
+  /// the next frame.
+  ///
+  /// @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
+  /// completion of |GetFrame()|. If success, a VideoFrame will be passed into
+  /// the completion callback function.
+  ///
+  /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
+  /// Returns PP_ERROR_NOMEMORY if |frame_buffer_size| frames buffer was not
+  /// allocated successfully.
+  int32_t GetFrame(
+      const CompletionCallbackWithOutput<VideoFrame>& cc);
+
+  /// Recycles a frame returned by |GetFrame()|, so the track can reuse
+  /// the underlaying buffer of this frame. And the frame will become invalid.
+  /// The caller should release all references it holds to |frame|, and not use
+  /// it anymore.
+  ///
+  /// @param[in] frame A VideoFrame returned by |GetFrame()|.
+  ///
+  /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
+  int32_t RecycleFrame(const VideoFrame& frame);
+
+  /// Closes the MediaStream video track, and disconnects it from video source.
+  /// After calling |Close()|, no new frames will be received.
+  void Close();
+
+};
+
+}  // namespace pp
+
+#endif  // PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_