New helper class AdaptedVideoSource.

webrtc/media/base/adaptedvideosource.h

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MEDIA_BASE_ADAPTEDVIDEOSOURCE_H_
+#define WEBRTC_MEDIA_BASE_ADAPTEDVIDEOSOURCE_H_
+
+#include "webrtc/base/timestampaligner.h"
+#include "webrtc/media/base/videoadapter.h"
+#include "webrtc/media/base/videobroadcaster.h"
+
+namespace rtc {
+
+class AdaptedVideoSource : public VideoBroadcaster {
+ public:
+  AdaptedVideoSource();
+
+  bool enable_video_adapter() const { return enable_video_adapter_; }
+  void set_enable_video_adapter(bool enable_video_adapter) {
+    enable_video_adapter_ = enable_video_adapter;
+  }
+  cricket::VideoAdapter* video_adapter() { return &video_adapter_; }
+
+  // Reports the appropriate frame size after adaptation. Returns true
+  // if a frame is wanted. Returns false if there are no interested
+  // sinks, or if the VideoAdapter decides to drop the frame.
+
+  // This function also implements timestamp translation/filtering.
+  // |camera_time_ns| is the camera's timestamp for the captured
+  // frame; it is expected to have good accuracy, but it may use an
+  // arbitrary epoch and a small possibly free-running with a frequency
+  // slightly different from the system clock. |system_time_us| is the
+  // monotonic system time (in the same scale as rtc::TimeMicros) when
+  // the frame was captured; the application is expected to read the
+  // system time as soon as possible after frame capture, but it may
+  // suffer scheduling jitter or poor system clock resolution. The
+  // output |translated_camera_time_us| is a combined timestamp,
+  // taking advantage of the supposedly higher accuracy in the camera
+  // timestamp, but using the same epoch and frequency as system time.
+  bool AdaptFrame(int width,
+                  int height,
+                  int64_t camera_time_us,
+                  int64_t system_time_us,
+                  int* out_width,
+                  int* out_height,
+                  int* crop_width,
+                  int* crop_height,
+                  int* crop_x,
+                  int* crop_y,
+                  int64_t* translated_camera_time_us);
+
+ protected:
+  void UpdateWants() EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);
+
+ private:
+  TimestampAligner timestamp_aligner_;
+  bool enable_video_adapter_;
+  cricket::VideoAdapter video_adapter_;
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_MEDIA_BASE_ADAPTEDVIDEOSOURCE_H_