2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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.
11 #ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
12 #define WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
14 #include "webrtc/modules/desktop_capture/shared_desktop_frame.h"
15 #include "webrtc/system_wrappers/interface/scoped_ptr.h"
16 #include "webrtc/typedefs.h"
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.
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.
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).
37 class ScreenCaptureFrameQueue {
39 ScreenCaptureFrameQueue();
40 ~ScreenCaptureFrameQueue();
42 // Moves to the next frame in the queue, moving the 'current' frame to become
43 // the 'previous' one.
44 void MoveToNextFrame();
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);
50 // Marks all frames obsolete and resets the previous frame pointer. No
51 // frames are freed though as the caller can still access them.
54 SharedDesktopFrame* current_frame() const {
55 return frames_[current_].get();
58 SharedDesktopFrame* previous_frame() const {
59 return frames_[(current_ + kQueueLength - 1) % kQueueLength].get();
63 // Index of the current frame.
66 static const int kQueueLength = 2;
67 scoped_ptr<SharedDesktopFrame> frames_[kQueueLength];
69 DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
74 #endif // WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_