From c5f152daa0853970ad38347062afc81e3229ff13 Mon Sep 17 00:00:00 2001
From: Sergey Silkin <ssilkin@webrtc.org>
Date: Wed, 26 Sep 2018 13:28:50 +0200
Subject: [PATCH] Mark all low layer frames as references if inter-layer pred
 is enabled.

Mark all low spatial layer frames as references (not just frames of
active low spatial layers) if inter-layer prediction is enabled since
these frames are indirect references of high spatial layer, which can
later be enabled without key frame.

Bug: webrtc:9782
Change-Id: Iffa5039fab2673a5582e7cdc9be4a36d9e8deb63
Reviewed-on: https://webrtc-review.googlesource.com/102063
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24849}
---
 .../codecs/vp9/test/vp9_impl_unittest.cc      | 25 +++++++++++++++++++
 modules/video_coding/codecs/vp9/vp9_impl.cc   |  9 ++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc b/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
index 6d2274f854..1b8c2ce876 100644
--- a/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
+++ b/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
@@ -499,6 +499,31 @@ TEST_F(TestVp9Impl,
   }
 }
 
+TEST_F(TestVp9Impl,
+       LowLayerMarkedAsRefIfHighLayerNotEncodedAndInterLayerPredIsEnabled) {
+  ConfigureSvc(3);
+  codec_settings_.VP9()->frameDroppingOn = false;
+  codec_settings_.VP9()->interLayerPred = InterLayerPredMode::kOn;
+
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
+            encoder_->InitEncode(&codec_settings_, 1 /* number of cores */,
+                                 0 /* max payload size (unused) */));
+
+  VideoBitrateAllocation bitrate_allocation;
+  bitrate_allocation.SetBitrate(
+      0, 0, codec_settings_.spatialLayers[0].targetBitrate * 1000);
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
+            encoder_->SetRateAllocation(bitrate_allocation,
+                                        codec_settings_.maxFramerate));
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
+            encoder_->Encode(*NextInputFrame(), nullptr, nullptr));
+  EncodedImage encoded_frame;
+  CodecSpecificInfo codec_info;
+  ASSERT_TRUE(WaitForEncodedFrame(&encoded_frame, &codec_info));
+  EXPECT_TRUE(codec_info.codecSpecific.VP9.ss_data_available);
+  EXPECT_FALSE(codec_info.codecSpecific.VP9.non_ref_for_inter_layer_pred);
+}
+
 TEST_F(TestVp9Impl, ScalabilityStructureIsAvailableInFlexibleMode) {
   codec_settings_.VP9()->flexibleMode = true;
   EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
diff --git a/modules/video_coding/codecs/vp9/vp9_impl.cc b/modules/video_coding/codecs/vp9/vp9_impl.cc
index e83a785cbe..998c65f9ba 100644
--- a/modules/video_coding/codecs/vp9/vp9_impl.cc
+++ b/modules/video_coding/codecs/vp9/vp9_impl.cc
@@ -856,10 +856,13 @@ void VP9EncoderImpl::PopulateCodecSpecific(CodecSpecificInfo* codec_specific,
   vp9_info->inter_layer_predicted =
       first_frame_in_picture ? false : is_inter_layer_pred_allowed;
 
-  const bool is_last_layer =
-      (layer_id.spatial_layer_id + 1 == num_active_spatial_layers_);
+  // Mark all low spatial layer frames as references (not just frames of
+  // active low spatial layers) if inter-layer prediction is enabled since
+  // these frames are indirect references of high spatial layer, which can
+  // later be enabled without key frame.
   vp9_info->non_ref_for_inter_layer_pred =
-      is_last_layer ? true : !is_inter_layer_pred_allowed;
+      !is_inter_layer_pred_allowed ||
+      layer_id.spatial_layer_id + 1 == num_spatial_layers_;
 
   // Always populate this, so that the packetizer can properly set the marker
   // bit.