[PPAPI] API definition for video media stream artifacts

ppapi/api/ppb_media_stream_video_track.idl

+/* 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.
+ */
+
+/**
+ * Defines the <code>PPB_MediaStreamVideoTrack</code> interface. Used for
+ * receiving video frames from a MediaStream video track in the browser.
+ * This interface is still in development (Dev API status) and may change.
+ */
+label Chrome {
+  [channel=dev] M34 = 0.1
+};
+
+/**
+ */
+interface PPB_MediaStreamVideoTrack {
+  /**
+   * Determines if a resource is a MediaStream video track resource.
+   *
+   * @param[in] resource The <code>PP_Resource</code> to test.
+   *
+   * @return A <code>PP_Bool</code> with <code>PP_TRUE</code> if the given
+   * resource is a Mediastream video track resource or <code>PP_FALSE</code>
+   * otherwise.
+   */
+  PP_Bool IsMediaStreamVideoTrack([in] PP_Resource resource);
+
+  /**
+   * 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

[yzshen1, 2013/12/26 18:52:38]

nit: it seems you use both || and <code></code>, it is better to be consistent
and change || to <code></code>. What do you think?

[Peng, 2013/12/27 01:37:52]

Sure. Done

+   * 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] video_track A <code>PP_Resource</code> corresponding to a video
+   * resource.
+   * @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([in] PP_Resource video_track,
+                    [in] uint32_t max_buffered_frames);
+
+  /**
+   * Returns the track ID of the underlying MediaStream video track.
+   *
+   * @param[in] video_track The <code>PP_Resource</code> to check.
+   *
+   * @return A <code>PP_Var</code> containing the MediaStream track ID as
+   * a string.
+   */
+  PP_Var GetId([in] PP_Resource video_track);
+
+  /**
+   * 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.
+   *
+   * @param[in] video_track The <code>PP_Resource</code> to check.
+   *
+   * @return A <code>PP_Bool</code> with <code>PP_TRUE</code> if the given
+   * MediaStream track has ended or <code>PP_FALSE</code> otherwise.
+   */
+  PP_Bool HasEnded([in] PP_Resource video_track);
+
+  /**
+   * 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.

[yzshen1, 2013/12/26 18:52:38]

(I have commented about this twice but you might not notice. You probably
haven't read the comments on older patchsets.)

I think you should also comment what would happen if the producer side is too
slow and currently there is no contents in the buffer, I think the completion
callback won't return until a frame arrives, right?

[Peng, 2013/12/27 01:37:52]

Sorry. I just used hotkey to navigate comments in very files. So I didn't see
the comment in only patchset.

Added comment about it. Done
Done

+   *
+   * @param[in] video_track A <code>PP_Resource</code> corresponding to a video
+   * resource.
+   * @param[out] frame A <code>PP_Resource</code> corresponding to a VideoFrame
+   * resource.
+   * @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
+   * completion of GetFrame().
+   *
+   * @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([in] PP_Resource video_track,
+                   [out] PP_Resource frame,
+                   [in] PP_CompletionCallback callback);
+
+  /**
+   * 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] video_track A <code>PP_Resource</code> corresponding to a video
+   * resource.
+   * @param[in] frame A <code>PP_Resource</code> corresponding to a VideoFrame
+   * resource returned by |GetFrame()|.
+   *
+   * @return An int32_t containing a result code from <code>pp_errors.h</code>.
+   */
+  int32_t RecycleFrame([in] PP_Resource video_track,
+                       [in] PP_Resource frame);
+
+  /**
+   * Closes the MediaStream video track, and disconnects it from video source.
+   * After calling |Close()|, no new frames will be received.
+   *
+   * @param[in] video_track A <code>PP_Resource</code> corresponding to a
+   * MediaStream video track resource.
+   */
+  void Close([in] PP_Resource video_track);
+};
+