From: Marco <marpan@google.com>
Date: Fri, 5 Jan 2018 17:33:27 +0000 (-0800)
Subject: vp9-svc: Use eightap_smooth for downsampling at low resol.
X-Git-Tag: v1.8.0~895^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=321f295632b1a66ac4de576f2f9fc99e150ac953;p=libvpx

vp9-svc: Use eightap_smooth for downsampling at low resol.

Switch from bilinear to eighttap_smooth for frame-level
downsampling at low resolutions (<= 320x240).

avgPSNR/SSIM metrics increase from ~0.5-2% (all clips positive gain),
for 2 and 3 spatial layer SVC, with 3 temporal layers.
Small/negligible increase in encoding time (< 1%).

Change-Id: I758472fc4fddd51d87f13c9d1a1cd4986ef5d41f
---

diff --git a/vp9/encoder/vp9_svc_layercontext.c b/vp9/encoder/vp9_svc_layercontext.c
index 2636bd9a5..4f137ecc3 100644
--- a/vp9/encoder/vp9_svc_layercontext.c
+++ b/vp9/encoder/vp9_svc_layercontext.c
@@ -661,6 +661,10 @@ int vp9_one_pass_cbr_svc_start_layer(VP9_COMP *const cpi) {
   // averaging filter), use bilinear for now.
   if (width * height <= 640 * 480) {
     cpi->svc.downsample_filter_type[cpi->svc.spatial_layer_id] = BILINEAR;
+    // Use Eightap_smooth for low resolutions.
+    if (width * height <= 320 * 240)
+      cpi->svc.downsample_filter_type[cpi->svc.spatial_layer_id] =
+          EIGHTTAP_SMOOTH;
     cpi->svc.downsample_filter_phase[cpi->svc.spatial_layer_id] = 8;
   }