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
14 #include "vp9/common/vp9_seg_common.h"
15
16 #include "vp9/encoder/vp9_segmentation.h"
17
18 #define AQ_C_SEGMENTS 3
19 #define AQ_C_STRENGTHS 3
20 static const int aq_c_active_segments[AQ_C_STRENGTHS] = {1, 2, 3};
21 static const double aq_c_q_adj_factor[AQ_C_STRENGTHS][AQ_C_SEGMENTS] =
22 {{1.0, 1.0, 1.0}, {1.0, 2.0, 1.0}, {1.0, 1.5, 2.5}};
23 static const double aq_c_transitions[AQ_C_STRENGTHS][AQ_C_SEGMENTS] =
24 {{1.0, 1.0, 1.0}, {1.0, 0.25, 0.0}, {1.0, 0.5, 0.25}};
25
get_aq_c_strength(int q_index,vpx_bit_depth_t bit_depth)26 static int get_aq_c_strength(int q_index, vpx_bit_depth_t bit_depth) {
27 // Approximate base quatizer (truncated to int)
28 const int base_quant = vp9_ac_quant(q_index, 0, bit_depth) / 4;
29 return (base_quant > 20) + (base_quant > 45);
30 }
31
vp9_setup_in_frame_q_adj(VP9_COMP * cpi)32 void vp9_setup_in_frame_q_adj(VP9_COMP *cpi) {
33 VP9_COMMON *const cm = &cpi->common;
34 struct segmentation *const seg = &cm->seg;
35
36 // Make SURE use of floating point in this function is safe.
37 vp9_clear_system_state();
38
39 if (cm->frame_type == KEY_FRAME ||
40 cpi->refresh_alt_ref_frame ||
41 (cpi->refresh_golden_frame && !cpi->rc.is_src_frame_alt_ref)) {
42 int segment;
43 const int aq_strength = get_aq_c_strength(cm->base_qindex, cm->bit_depth);
44 const int active_segments = aq_c_active_segments[aq_strength];
45
46 // Clear down the segment map.
47 vpx_memset(cpi->segmentation_map, 0, cm->mi_rows * cm->mi_cols);
48
49 // Clear down the complexity map used for rd.
50 vpx_memset(cpi->complexity_map, 0, cm->mi_rows * cm->mi_cols);
51
52 vp9_clearall_segfeatures(seg);
53
54 // Segmentation only makes sense if the target bits per SB is above a
55 // threshold. Below this the overheads will usually outweigh any benefit.
56 if (cpi->rc.sb64_target_rate < 256) {
57 vp9_disable_segmentation(seg);
58 return;
59 }
60
61 vp9_enable_segmentation(seg);
62
63 // Select delta coding method.
64 seg->abs_delta = SEGMENT_DELTADATA;
65
66 // Segment 0 "Q" feature is disabled so it defaults to the baseline Q.
67 vp9_disable_segfeature(seg, 0, SEG_LVL_ALT_Q);
68
69 // Use some of the segments for in frame Q adjustment.
70 for (segment = 1; segment < active_segments; ++segment) {
71 int qindex_delta =
72 vp9_compute_qdelta_by_rate(&cpi->rc, cm->frame_type, cm->base_qindex,
73 aq_c_q_adj_factor[aq_strength][segment],
74 cm->bit_depth);
75
76 // For AQ complexity mode, we dont allow Q0 in a segment if the base
77 // Q is not 0. Q0 (lossless) implies 4x4 only and in AQ mode 2 a segment
78 // Q delta is sometimes applied without going back around the rd loop.
79 // This could lead to an illegal combination of partition size and q.
80 if ((cm->base_qindex != 0) && ((cm->base_qindex + qindex_delta) == 0)) {
81 qindex_delta = -cm->base_qindex + 1;
82 }
83 if ((cm->base_qindex + qindex_delta) > 0) {
84 vp9_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
85 vp9_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
86 }
87 }
88 }
89 }
90
91 // Select a segment for the current SB64 block.
92 // The choice of segment for a block depends on the ratio of the projected
93 // bits for the block vs a target average.
94 // An "aq_strength" value determines how many segments are supported,
95 // the set of transition points to use and the extent of the quantizer
96 // adjustment for each segment (configured in vp9_setup_in_frame_q_adj()).
vp9_select_in_frame_q_segment(VP9_COMP * cpi,int mi_row,int mi_col,int output_enabled,int projected_rate)97 void vp9_select_in_frame_q_segment(VP9_COMP *cpi,
98 int mi_row, int mi_col,
99 int output_enabled, int projected_rate) {
100 VP9_COMMON *const cm = &cpi->common;
101
102 const int mi_offset = mi_row * cm->mi_cols + mi_col;
103 const int bw = num_8x8_blocks_wide_lookup[BLOCK_64X64];
104 const int bh = num_8x8_blocks_high_lookup[BLOCK_64X64];
105 const int xmis = MIN(cm->mi_cols - mi_col, bw);
106 const int ymis = MIN(cm->mi_rows - mi_row, bh);
107 int complexity_metric = 64;
108 int x, y;
109
110 unsigned char segment;
111
112 if (!output_enabled) {
113 segment = 0;
114 } else {
115 // Rate depends on fraction of a SB64 in frame (xmis * ymis / bw * bh).
116 // It is converted to bits * 256 units.
117 const int target_rate = (cpi->rc.sb64_target_rate * xmis * ymis * 256) /
118 (bw * bh);
119 const int aq_strength = get_aq_c_strength(cm->base_qindex, cm->bit_depth);
120 const int active_segments = aq_c_active_segments[aq_strength];
121
122 // The number of segments considered and the transition points used to
123 // select them is determined by the "aq_strength" value.
124 // Currently this loop only supports segments that reduce Q (i.e. where
125 // there is undershoot.
126 // The loop counts down towards segment 0 which is the default segment
127 // with no Q adjustment.
128 segment = active_segments - 1;
129 while (segment > 0) {
130 if (projected_rate <
131 (target_rate * aq_c_transitions[aq_strength][segment])) {
132 break;
133 }
134 --segment;
135 }
136
137 if (target_rate > 0) {
138 complexity_metric =
139 clamp((int)((projected_rate * 64) / target_rate), 16, 255);
140 }
141 }
142
143 // Fill in the entires in the segment map corresponding to this SB64.
144 for (y = 0; y < ymis; y++) {
145 for (x = 0; x < xmis; x++) {
146 cpi->segmentation_map[mi_offset + y * cm->mi_cols + x] = segment;
147 cpi->complexity_map[mi_offset + y * cm->mi_cols + x] =
148 (unsigned char)complexity_metric;
149 }
150 }
151 }
152