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 20static const int aq_c_active_segments[AQ_C_STRENGTHS] = {1, 2, 3}; 21static 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}}; 23static 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 26static 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 32void 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()). 97void 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