screen_capture_frame_queue.h (2758B)
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 MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_ 12 #define MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_ 13 14 #include <memory> 15 16 namespace webrtc { 17 18 // Represents a queue of reusable video frames. Provides access to the 'current' 19 // frame - the frame that the caller is working with at the moment, and to the 20 // 'previous' frame - the predecessor of the current frame swapped by 21 // MoveToNextFrame() call, if any. 22 // 23 // The caller is expected to (re)allocate frames if current_frame() returns 24 // NULL. The caller can mark all frames in the queue for reallocation (when, 25 // say, frame dimensions change). The queue records which frames need updating 26 // which the caller can query. 27 // 28 // Frame consumer is expected to never hold more than kQueueLength frames 29 // created by this function and it should release the earliest one before trying 30 // to capture a new frame (i.e. before MoveToNextFrame() is called). 31 template <typename FrameType> 32 class ScreenCaptureFrameQueue { 33 public: 34 ScreenCaptureFrameQueue() = default; 35 ~ScreenCaptureFrameQueue() = default; 36 37 ScreenCaptureFrameQueue(const ScreenCaptureFrameQueue&) = delete; 38 ScreenCaptureFrameQueue& operator=(const ScreenCaptureFrameQueue&) = delete; 39 40 // Moves to the next frame in the queue, moving the 'current' frame to become 41 // the 'previous' one. 42 void MoveToNextFrame() { current_ = (current_ + 1) % kQueueLength; } 43 44 // Replaces the current frame with a new one allocated by the caller. The 45 // existing frame (if any) is destroyed. Takes ownership of `frame`. 46 void ReplaceCurrentFrame(std::unique_ptr<FrameType> frame) { 47 frames_[current_] = std::move(frame); 48 } 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 for (int i = 0; i < kQueueLength; i++) { 54 frames_[i].reset(); 55 } 56 current_ = 0; 57 } 58 59 FrameType* current_frame() const { return frames_[current_].get(); } 60 61 FrameType* previous_frame() const { 62 return frames_[(current_ + kQueueLength - 1) % kQueueLength].get(); 63 } 64 65 private: 66 // Index of the current frame. 67 int current_ = 0; 68 69 static const int kQueueLength = 2; 70 std::unique_ptr<FrameType> frames_[kQueueLength]; 71 }; 72 73 } // namespace webrtc 74 75 #endif // MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_