1/*
2 *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11#ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
12#define WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
13
14#include "webrtc/modules/desktop_capture/shared_desktop_frame.h"
15#include "webrtc/system_wrappers/interface/scoped_ptr.h"
16#include "webrtc/typedefs.h"
17
18namespace webrtc {
19class DesktopFrame;
20}  // namespace webrtc
21
22namespace webrtc {
23
24// Represents a queue of reusable video frames. Provides access to the 'current'
25// frame - the frame that the caller is working with at the moment, and to the
26// 'previous' frame - the predecessor of the current frame swapped by
27// MoveToNextFrame() call, if any.
28//
29// The caller is expected to (re)allocate frames if current_frame() returns
30// NULL. The caller can mark all frames in the queue for reallocation (when,
31// say, frame dimensions change). The queue records which frames need updating
32// which the caller can query.
33//
34// Frame consumer is expected to never hold more than kQueueLength frames
35// created by this function and it should release the earliest one before trying
36// to capture a new frame (i.e. before MoveToNextFrame() is called).
37class ScreenCaptureFrameQueue {
38 public:
39  ScreenCaptureFrameQueue();
40  ~ScreenCaptureFrameQueue();
41
42  // Moves to the next frame in the queue, moving the 'current' frame to become
43  // the 'previous' one.
44  void MoveToNextFrame();
45
46  // Replaces the current frame with a new one allocated by the caller. The
47  // existing frame (if any) is destroyed. Takes ownership of |frame|.
48  void ReplaceCurrentFrame(DesktopFrame* frame);
49
50  // Marks all frames obsolete and resets the previous frame pointer. No
51  // frames are freed though as the caller can still access them.
52  void Reset();
53
54  SharedDesktopFrame* current_frame() const {
55    return frames_[current_].get();
56  }
57
58  SharedDesktopFrame* previous_frame() const {
59    return frames_[(current_ + kQueueLength - 1) % kQueueLength].get();
60  }
61
62 private:
63  // Index of the current frame.
64  int current_;
65
66  static const int kQueueLength = 2;
67  scoped_ptr<SharedDesktopFrame> frames_[kQueueLength];
68
69  DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
70};
71
72}  // namespace webrtc
73
74#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
75