VideoAdapter: Drop frames based on actual fps instead of expected fps

webrtc/media/base/videoadapter.h

 /*
  *  Copyright (c) 2010 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_VIDEOADAPTER_H_
 #define WEBRTC_MEDIA_BASE_VIDEOADAPTER_H_
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/optional.h"
 #include "webrtc/media/base/videocommon.h"
 
 namespace cricket {
 
 // VideoAdapter adapts an input video frame to an output frame based on the
 // specified input and output formats. The adaptation includes dropping frames
 // to reduce frame rate and scaling frames.
 // VideoAdapter is thread safe.
 class VideoAdapter {
  public:
   VideoAdapter();
   virtual ~VideoAdapter();
 
-  // Sets the expected frame interval. This controls how often frames should
-  // be dropped if |OnOutputFormatRequest| is called with a lower frame
-  // interval.
-  void SetExpectedInputFrameInterval(int64_t interval);
-
   // Return the adapted resolution given the input resolution. The input
   // resolution should first be cropped to the specified resolution, and then
   // scaled to the final output resolution. The output resolution will be 0x0 if
   // the frame should be dropped.
   void AdaptFrameResolution(int in_width,
                             int in_height,
+                            int64_t in_timestamp_ns,
                             int* cropped_width,
                             int* cropped_height,
                             int* out_width,
                             int* out_height);
 
   // Requests the output frame size and frame interval from
   // |AdaptFrameResolution| to not be larger than |format|. Also, the input
   // frame size will be cropped to match the requested aspect ratio. The
   // requested aspect ratio is orientation agnostic and will be adjusted to
   // maintain the input orientation, so it doesn't matter if e.g. 1280x720 or
   // 720x1280 is requested.
   void OnOutputFormatRequest(const VideoFormat& format);
 
   // Requests the output frame size from |AdaptFrameResolution| to not have
   // more than |max_pixel_count| pixels and have "one step" up more pixels than
   // max_pixel_count_step_up.
   void OnResolutionRequest(rtc::Optional<int> max_pixel_count,
                            rtc::Optional<int> max_pixel_count_step_up);
 
  private:
+  // Determine if frame should be dropped based on input fps and requested fps.
+  bool KeepFrame(int64_t in_timestamp_ns);
+
   int frames_in_;         // Number of input frames.
   int frames_out_;        // Number of output frames.
   int frames_scaled_;     // Number of frames scaled.
   int adaption_changes_;  // Number of changes in scale factor.
   int previous_width_;    // Previous adapter output width.
   int previous_height_;   // Previous adapter output height.
-  int input_interval_ GUARDED_BY(critical_section_);
-  int64_t interval_next_frame_ GUARDED_BY(critical_section_);
+  // The target timestamp for the next frame based on requested format.
+  rtc::Optional<int64_t> next_frame_timestamp_ns_ GUARDED_BY(critical_section_);
 
   // Max number of pixels requested via calls to OnOutputFormatRequest,
   // OnResolutionRequest respectively.
   // The adapted output format is the minimum of these.
   rtc::Optional<VideoFormat> requested_format_ GUARDED_BY(critical_section_);
   int resolution_request_max_pixel_count_ GUARDED_BY(critical_section_);
   int resolution_request_max_pixel_count_step_up_ GUARDED_BY(critical_section_);
 
   // The critical section to protect the above variables.
   rtc::CriticalSection critical_section_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(VideoAdapter);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_BASE_VIDEOADAPTER_H_