ref: 50a90744407be7b88c47737d1bba79e7ffb5c2d3
parent: f2c039115d8c63e19a8f5fab765360f0be672d41
author: Jingning Han <jingning@google.com>
date: Mon Oct 29 10:08:20 EDT 2018
Properly space qp in q mode for multi-layer ARF
Space the quantization parameter distribution according to the
layer depth for multi-layer ARF coding structure. This allows
lower layers to have relatively smaller quantization parameters
than higher layers. It improves the compression performance
in constant q mode for multi-layer ARF system:
avg PSNR overall PSNR SSIM
lowres -0.33% -0.31% -1.44%
midres -0.29% -0.38% -1.14%
hdres -0.27% -0.49% -1.02%
Change-Id: I9cfe2f27e6c0029c30614970a46de3045840264e
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -1303,8 +1303,14 @@
// Modify best quality for second level arfs. For mode VPX_Q this
// becomes the baseline frame q.
- if (gf_group->rf_level[gf_group_index] == GF_ARF_LOW)
- active_best_quality = (active_best_quality + cq_level + 1) / 2;
+ if (gf_group->rf_level[gf_group_index] == GF_ARF_LOW) {+ const int layer_depth = gf_group->layer_depth[gf_group_index];
+ // linearly fit the frame q depending on the layer depth index from
+ // the base layer ARF.
+ active_best_quality = ((layer_depth - 1) * cq_level +
+ active_best_quality + layer_depth / 2) /
+ layer_depth;
+ }
}
} else {active_best_quality = get_gf_active_quality(cpi, q, cm->bit_depth);