Video Capture Pepper API

ppapi/c/dev/ppp_video_capture_dev.h

+/* Copyright (c) 2011 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_C_DEV_PPP_VIDEO_CAPTURE_DEV_H_
+#define PPAPI_C_DEV_PPP_VIDEO_CAPTURE_DEV_H_
+
+#include "ppapi/c/dev/pp_video_capture_dev.h"
+#include "ppapi/c/pp_instance.h"
+#include "ppapi/c/pp_resource.h"
+#include "ppapi/c/pp_stdint.h"
+
+#define PPP_VIDEO_CAPTURE_DEV_INTERFACE_0_1 "PPP_VideoCapture(Dev);0.1"
+#define PPP_VIDEO_CAPTURE_DEV_INTERFACE PPP_VIDEO_CAPTURE_DEV_INTERFACE_0_1
+
+/**
+ * Video Capture client interface. See |PPB_VideoCapture_Dev| for general theory
+ * of operation.
+ */
+struct PPP_VideoCapture_Dev {

[darin (slow to review), 2011/08/02 18:02:59]

it is necessary to have PPP_VideoCapture_Dev?  Can you instead make
PPB_VideoCapture_Dev provide getters for "device-info", "status", "error" and
"buffer-ready" state?  Then, it seems like you just need a way to get a
notification when state changes occur.  That's what PP_CompletionCallback is
for.

[piman, 2011/08/03 21:45:38]

After discussion with Darin, we decided to go ahead with this now, and revisit a
callback-based approach before considering the API for stabilization.

+  /**
+   * Signals the capture device information, such as resolution and frame rate,
+   * and the array of buffers that the browser will use to send pixel data.
+   *
+   * |info| is a pointer to the PP_VideoCaptureDeviceInfo_Dev structure
+   * containing resolution and frame rate.
+   * |buffer_count| is the number of buffers, and |buffers| is the array of
+   * PPB_Buffer_Dev buffers.
+   *
+   * Note: the buffers are passed without an extra reference. The plugin is
+   * expected to add its own references to the buffers.
+   */
+  void (*OnDeviceInfo)(PP_Instance instance,

[brettw, 2011/08/02 17:17:44]

Do these functions really need the instance? Normally I would expect just to be
given the resource.

[piman, 2011/08/03 00:44:41]

All functions in other PPP interfaces that apply to a resource work this way, so
the first argument is consistency.
In theory, it doesn't have to be, because one could keep resource->instance
maps. However, that pattern needs to be replicated in both proxies as well as
the plugins. Map look-ups add a bit of complexity (code complexity as well as
run-time complexity), but we get this instance parameter for free (including in
the proxies). Lastly, we don't currently have a way to associate PPP
implementations to resources in the module, only to instances. Again could be
fixed, but since this comes for free, I tend to like it that way. If you feel
strongly about it, let me know.

+                       PP_Resource video_capture,
+                       const struct PP_VideoCaptureDeviceInfo_Dev* info,
+                       uint32_t buffer_count,
+                       const PP_Resource* buffers);
+
+  /**
+   * Signals status changes on the VideoCapture. |status| is a
+   * one of the values from PP_VideoCaptureDeviceInfo_Dev;

[wjia(left Chromium), 2011/08/02 16:22:28]

PP_VideoCaptureStatus_Dev?

[piman, 2011/08/03 00:44:41]

Done.

+   */
+  void (*OnStatus)(PP_Instance instance,
+                   PP_Resource video_capture,
+                   uint32_t status);
+
+  /**
+   * Signals an error from the video capture system.
+   *
+   * Errors that can be generated:
+   * - PP_ERROR_NOMEMORY: not enough memory was available to allocate buffers.
+   * - PP_ERROR_FAILED: video capture could not start.
+   */
+  void (*OnError)(PP_Instance instance,
+                  PP_Resource video_capture,
+                  uint32_t error_code);
+
+  /**
+   * Signals that a buffer is available for consumption by the plugin.
+   *
+   * |buffer| is the index of the buffer, in the array returned by OnDeviceInfo.
+   */
+  void (*OnBufferReady)(PP_Instance,
+                        PP_Resource video_capture,
+                        uint32_t buffer);
+};
+
+#endif  /* PPAPI_C_DEV_PPP_VIDEO_CAPTURE_DEV_H_ */
+