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1 /*
2  *  Copyright (c) 2014 The WebM project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #include <limits.h>
12 #include <math.h>
13 #include "vpx_dsp/vpx_dsp_common.h"
14 #include "vpx_ports/system_state.h"
15 
16 #include "vp9/encoder/vp9_aq_complexity.h"
17 #include "vp9/encoder/vp9_aq_variance.h"
18 #include "vp9/encoder/vp9_encodeframe.h"
19 #include "vp9/common/vp9_seg_common.h"
20 #include "vp9/encoder/vp9_segmentation.h"
21 
22 #define AQ_C_SEGMENTS 5
23 #define DEFAULT_AQ2_SEG 3  // Neutral Q segment
24 #define AQ_C_STRENGTHS 3
25 static const double aq_c_q_adj_factor[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
26   { 1.75, 1.25, 1.05, 1.00, 0.90 },
27   { 2.00, 1.50, 1.15, 1.00, 0.85 },
28   { 2.50, 1.75, 1.25, 1.00, 0.80 }
29 };
30 static const double aq_c_transitions[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
31   { 0.15, 0.30, 0.55, 2.00, 100.0 },
32   { 0.20, 0.40, 0.65, 2.00, 100.0 },
33   { 0.25, 0.50, 0.75, 2.00, 100.0 }
34 };
35 static const double aq_c_var_thresholds[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
36   { -4.0, -3.0, -2.0, 100.00, 100.0 },
37   { -3.5, -2.5, -1.5, 100.00, 100.0 },
38   { -3.0, -2.0, -1.0, 100.00, 100.0 }
39 };
40 
get_aq_c_strength(int q_index,vpx_bit_depth_t bit_depth)41 static int get_aq_c_strength(int q_index, vpx_bit_depth_t bit_depth) {
42   // Approximate base quatizer (truncated to int)
43   const int base_quant = vp9_ac_quant(q_index, 0, bit_depth) / 4;
44   return (base_quant > 10) + (base_quant > 25);
45 }
46 
vp9_setup_in_frame_q_adj(VP9_COMP * cpi)47 void vp9_setup_in_frame_q_adj(VP9_COMP *cpi) {
48   VP9_COMMON *const cm = &cpi->common;
49   struct segmentation *const seg = &cm->seg;
50 
51   // Make SURE use of floating point in this function is safe.
52   vpx_clear_system_state();
53 
54   if (frame_is_intra_only(cm) || cm->error_resilient_mode ||
55       cpi->refresh_alt_ref_frame || cpi->force_update_segmentation ||
56       (cpi->refresh_golden_frame && !cpi->rc.is_src_frame_alt_ref)) {
57     int segment;
58     const int aq_strength = get_aq_c_strength(cm->base_qindex, cm->bit_depth);
59 
60     // Clear down the segment map.
61     memset(cpi->segmentation_map, DEFAULT_AQ2_SEG, cm->mi_rows * cm->mi_cols);
62 
63     vp9_clearall_segfeatures(seg);
64 
65     // Segmentation only makes sense if the target bits per SB is above a
66     // threshold. Below this the overheads will usually outweigh any benefit.
67     if (cpi->rc.sb64_target_rate < 256) {
68       vp9_disable_segmentation(seg);
69       return;
70     }
71 
72     vp9_enable_segmentation(seg);
73 
74     // Select delta coding method.
75     seg->abs_delta = SEGMENT_DELTADATA;
76 
77     // Default segment "Q" feature is disabled so it defaults to the baseline Q.
78     vp9_disable_segfeature(seg, DEFAULT_AQ2_SEG, SEG_LVL_ALT_Q);
79 
80     // Use some of the segments for in frame Q adjustment.
81     for (segment = 0; segment < AQ_C_SEGMENTS; ++segment) {
82       int qindex_delta;
83 
84       if (segment == DEFAULT_AQ2_SEG) continue;
85 
86       qindex_delta = vp9_compute_qdelta_by_rate(
87           &cpi->rc, cm->frame_type, cm->base_qindex,
88           aq_c_q_adj_factor[aq_strength][segment], cm->bit_depth);
89 
90       // For AQ complexity mode, we dont allow Q0 in a segment if the base
91       // Q is not 0. Q0 (lossless) implies 4x4 only and in AQ mode 2 a segment
92       // Q delta is sometimes applied without going back around the rd loop.
93       // This could lead to an illegal combination of partition size and q.
94       if ((cm->base_qindex != 0) && ((cm->base_qindex + qindex_delta) == 0)) {
95         qindex_delta = -cm->base_qindex + 1;
96       }
97       if ((cm->base_qindex + qindex_delta) > 0) {
98         vp9_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
99         vp9_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
100       }
101     }
102   }
103 }
104 
105 #define DEFAULT_LV_THRESH 10.0
106 #define MIN_DEFAULT_LV_THRESH 8.0
107 // Select a segment for the current block.
108 // The choice of segment for a block depends on the ratio of the projected
109 // bits for the block vs a target average and its spatial complexity.
vp9_caq_select_segment(VP9_COMP * cpi,MACROBLOCK * mb,BLOCK_SIZE bs,int mi_row,int mi_col,int projected_rate)110 void vp9_caq_select_segment(VP9_COMP *cpi, MACROBLOCK *mb, BLOCK_SIZE bs,
111                             int mi_row, int mi_col, int projected_rate) {
112   VP9_COMMON *const cm = &cpi->common;
113 
114   const int mi_offset = mi_row * cm->mi_cols + mi_col;
115   const int bw = num_8x8_blocks_wide_lookup[BLOCK_64X64];
116   const int bh = num_8x8_blocks_high_lookup[BLOCK_64X64];
117   const int xmis = VPXMIN(cm->mi_cols - mi_col, num_8x8_blocks_wide_lookup[bs]);
118   const int ymis = VPXMIN(cm->mi_rows - mi_row, num_8x8_blocks_high_lookup[bs]);
119   int x, y;
120   int i;
121   unsigned char segment;
122 
123   if (0) {
124     segment = DEFAULT_AQ2_SEG;
125   } else {
126     // Rate depends on fraction of a SB64 in frame (xmis * ymis / bw * bh).
127     // It is converted to bits * 256 units.
128     const int target_rate =
129         (cpi->rc.sb64_target_rate * xmis * ymis * 256) / (bw * bh);
130     double logvar;
131     double low_var_thresh;
132     const int aq_strength = get_aq_c_strength(cm->base_qindex, cm->bit_depth);
133 
134     vpx_clear_system_state();
135     low_var_thresh = (cpi->oxcf.pass == 2) ? VPXMAX(cpi->twopass.mb_av_energy,
136                                                     MIN_DEFAULT_LV_THRESH)
137                                            : DEFAULT_LV_THRESH;
138 
139     vp9_setup_src_planes(mb, cpi->Source, mi_row, mi_col);
140     logvar = vp9_log_block_var(cpi, mb, bs);
141 
142     segment = AQ_C_SEGMENTS - 1;  // Just in case no break out below.
143     for (i = 0; i < AQ_C_SEGMENTS; ++i) {
144       // Test rate against a threshold value and variance against a threshold.
145       // Increasing segment number (higher variance and complexity) = higher Q.
146       if ((projected_rate < target_rate * aq_c_transitions[aq_strength][i]) &&
147           (logvar < (low_var_thresh + aq_c_var_thresholds[aq_strength][i]))) {
148         segment = i;
149         break;
150       }
151     }
152   }
153 
154   // Fill in the entires in the segment map corresponding to this SB64.
155   for (y = 0; y < ymis; y++) {
156     for (x = 0; x < xmis; x++) {
157       cpi->segmentation_map[mi_offset + y * cm->mi_cols + x] = segment;
158     }
159   }
160 }
161