iOS h264: Request keyframe after coming back from background.

webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_encoder.cc

 /*
  *  Copyright (c) 2015 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.
  *
  */
@@ skipping 230 matching lines @@
   if (!callback_ || !compression_session_) {
     return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
   }
 #if defined(WEBRTC_IOS)
   if (!RTCIsUIApplicationActive()) {
     // Ignore all encode requests when app isn't active. In this state, the
     // hardware encoder has been invalidated by the OS.
     return WEBRTC_VIDEO_CODEC_OK;
   }
 #endif
+  bool is_keyframe_required = false;
   // Get a pixel buffer from the pool and copy frame data over.
   CVPixelBufferPoolRef pixel_buffer_pool =
       VTCompressionSessionGetPixelBufferPool(compression_session_);
 #if defined(WEBRTC_IOS)
   if (!pixel_buffer_pool) {
     // Kind of a hack. On backgrounding, the compression session seems to get
     // invalidated, which causes this pool call to fail when the application
     // is foregrounded and frames are being sent for encoding again.
     // Resetting the session when this happens fixes the issue.
+    // In addition we request a keyframe so video can recover quickly.
     ResetCompressionSession();
     pixel_buffer_pool =
         VTCompressionSessionGetPixelBufferPool(compression_session_);
+    is_keyframe_required = true;
   }
 #endif
   if (!pixel_buffer_pool) {
     LOG(LS_ERROR) << "Failed to get pixel buffer pool.";
     return WEBRTC_VIDEO_CODEC_ERROR;
   }
   CVPixelBufferRef pixel_buffer = nullptr;
   CVReturn ret = CVPixelBufferPoolCreatePixelBuffer(nullptr, pixel_buffer_pool,
                                                     &pixel_buffer);
   if (ret != kCVReturnSuccess) {
     LOG(LS_ERROR) << "Failed to create pixel buffer: " << ret;
     // We probably want to drop frames here, since failure probably means
     // that the pool is empty.
     return WEBRTC_VIDEO_CODEC_ERROR;
   }
   RTC_DCHECK(pixel_buffer);
   if (!internal::CopyVideoFrameToPixelBuffer(input_image, pixel_buffer)) {
     LOG(LS_ERROR) << "Failed to copy frame data.";
     CVBufferRelease(pixel_buffer);
     return WEBRTC_VIDEO_CODEC_ERROR;
   }
 
   // Check if we need a keyframe.
-  bool is_keyframe_required = false;
-  if (frame_types) {
+  if (!is_keyframe_required && frame_types) {
     for (auto frame_type : *frame_types) {
       if (frame_type == kVideoFrameKey) {
         is_keyframe_required = true;
         break;
       }
     }
   }
 
   CMTime presentation_time_stamp =
       CMTimeMake(input_image.render_time_ms(), 1000);
@@ skipping 216 matching lines @@
   if (result != 0) {
     LOG(LS_ERROR) << "Encode callback failed: " << result;
     return;
   }
   bitrate_adjuster_.Update(frame._size);
 }
 
 }  // namespace webrtc
 
 #endif  // defined(WEBRTC_VIDEO_TOOLBOX_SUPPORTED)