commit 58ebf8d4a207576cdee98ddda312e921f316b18d
author Jingning Han <jingning@google.com> Tue Jun 29 23:37:33 2021 -0700
committer Jingning Han <jingning@google.com> Wed Jun 30 17:13:15 2021 +0000
tree 4994c8c4c407085035abaa14be68e1d8435b4c12
parent 493e02b3d012d9ffb7510cf56ae5e6f3799cc074

Fix temporal filtering for forward key frame

Correctly use frames on both sides as the reference. When the
forward key frame distance is 32, this improves the compression
efficiency by 1.05% in PSNR BD-rate and 0.75% in SSIM BD-rate.

BUG=aomedia:3079

Change-Id: Ib6eea9cf039b713be6b772e19e27fafbf2b5ebe7

av1/encoder/temporal_filter.c

diff --git a/av1/encoder/temporal_filter.c b/av1/encoder/temporal_filter.c
index 717163b..f9cb1d8 100644
--- a/av1/encoder/temporal_filter.c
+++ b/av1/encoder/temporal_filter.c
@@ -936,13 +936,16 @@
  *                              used for filtering.
  * \param[in]   update_type     This frame's update type.
  *
+ * \param[in]   is_forward_keyframe Indicate whether this is a forward keyframe.
+ *
  * \return Nothing will be returned. But the fields `frames`, `num_frames`,
  *         `filter_frame_idx` and `noise_levels` will be updated in cpi->tf_ctx.
  */
 static void tf_setup_filtering_buffer(AV1_COMP *cpi,
                                       const int filter_frame_lookahead_idx,
                                       const int is_second_arf,
-                                      FRAME_UPDATE_TYPE update_type) {
+                                      FRAME_UPDATE_TYPE update_type,
+                                      int is_forward_keyframe) {
   TemporalFilterCtx *tf_ctx = &cpi->tf_ctx;
   YV12_BUFFER_CONFIG **frames = tf_ctx->frames;
   // Number of frames used for filtering. Set `arnr_max_frames` as 1 to disable
@@ -1025,7 +1028,7 @@
   num_frames = AOMMIN(num_frames + adjust_num, lookahead_depth);
 
   if (frame_type == KEY_FRAME) {
-    num_before = 0;
+    num_before = is_forward_keyframe ? num_frames / 2 : 0;
     num_after = AOMMIN(num_frames - 1, max_after);
   } else {
     num_frames = AOMMIN(num_frames, cpi->ppi->p_rc.gfu_boost / 150);
@@ -1144,7 +1147,7 @@
   tf_ctx->num_frames = 0;
   tf_ctx->filter_frame_idx = -1;
   tf_setup_filtering_buffer(cpi, filter_frame_lookahead_idx, is_second_arf,
-                            update_type);
+                            update_type, is_forward_keyframe);
   assert(tf_ctx->num_frames > 0);
   assert(tf_ctx->filter_frame_idx < tf_ctx->num_frames);