sender: send only 1 keyframe at start

Don't choke the network connection with multiple keyframes in
succession. Only 1 keyframe should be necessary.

Change-Id: I6c1bcc4c3973fd6cb7eb58a9928e823bc0c5fcf7

src/media/video/video_sender.cpp

@@ -4,6 +4,7 @@
  *  Author: Tristan Matthews <tristan.matthews@savoirfairelinux.com>
  *  Author: Guillaume Roguez <Guillaume.Roguez@savoirfairelinux.com>
  *  Author: Eloi Bail <eloi.bail@savoirfairelinux.com>
+ *  Author: Philippe Gorley <philippe.gorley@savoirfairelinux.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -78,7 +79,7 @@ VideoSender::encodeAndSendVideo(VideoFrame& input_frame)
 #if __ANDROID__
         if (forceKeyFrame_) {
             emitSignal<DRing::VideoSignal::RequestKeyFrame>();
-            forceKeyFrame_ = 0;
+            --forceKeyFrame_;
         }
 #endif
         int size {0};

src/media/video/video_sender.h

@@ -63,7 +63,7 @@ public:
     int setBitrate(uint64_t br);
 
 private:
-    static constexpr int KEYFRAMES_AT_START {4}; // Number of keyframes to enforce at stream startup
+    static constexpr int KEYFRAMES_AT_START {1}; // Number of keyframes to enforce at stream startup
     static constexpr unsigned KEY_FRAME_PERIOD {0}; // seconds before forcing a keyframe
 
     NON_COPYABLE(VideoSender);
@@ -74,7 +74,6 @@ private:
     std::unique_ptr<MediaIOHandle> muxContext_ = nullptr;
     std::unique_ptr<MediaEncoder> videoEncoder_ = nullptr;
 
-    // XXX forceKeyFrame_ is always at -1, incremented to 0 when a keyframe is requested (still works though)
     std::atomic<int> forceKeyFrame_ {KEYFRAMES_AT_START};
     int keyFrameFreq_ {0}; // Set keyframe rate, 0 to disable auto-keyframe. Computed in constructor
     int64_t frameNumber_ = 0;