shithub: libvpx

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vp9: SVC: Set downsample filtertype for lowest spatial layer.

For lowest spatial layer, in 3 layer SVC, set the
downsampling filtertype to get averaging filter.
Needed for reducing aliasing on low-res layer,
small increase in overall encoder time.

Change-Id: Ia31460123bd91b72eca49b46dd924b9f226d4563

--- a/vp9/encoder/vp9_svc_layercontext.c

+++ b/vp9/encoder/vp9_svc_layercontext.c

@@ -651,6 +651,10 @@

                        lc->scaling_factor_num, lc->scaling_factor_den, &width,

                        &height);

+  // For 3 spatial layers, on the lowest resolution layer: set the filtertype

+  // for downsampling source to 1, to get averaging filter.

+  if (cpi->svc.number_spatial_layers == 3)

+    cpi->svc.filtertype_downsample_source[0] = 1;

   // The usage of use_base_mv assumes down-scale of 2x2. For now, turn off use

   // of base motion vectors if spatial scale factors for any layers are not 2,

   // keep the case of 3 spatial layers with scale factor of 4x4 for base layer.