ref: 12aaff560b0615c6ebce1f707251a1bbead3d7f3
dir: /vp9/encoder/vp9_aq_complexity.c/
/*
* Copyright (c) 2014 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <limits.h>
#include <math.h>
#include "vp9/common/vp9_seg_common.h"
#include "vp9/encoder/vp9_segmentation.h"
#define AQ_C_SEGMENTS 3
#define AQ_C_STRENGTHS 3
static const int aq_c_active_segments[AQ_C_STRENGTHS] = {1, 2, 3};
static const double aq_c_q_adj_factor[AQ_C_STRENGTHS][AQ_C_SEGMENTS] =
{{1.0, 1.0, 1.0}, {1.0, 2.0, 1.0}, {1.0, 1.5, 2.5}};
static const double aq_c_transitions[AQ_C_STRENGTHS][AQ_C_SEGMENTS] =
{{1.0, 1.0, 1.0}, {1.0, 0.25, 0.0}, {1.0, 0.5, 0.25}};
static int get_aq_c_strength(int q_index) {
// Approximate base quatizer (truncated to int)
int base_quant = vp9_ac_quant(q_index, 0) / 4;
return (base_quant > 20) + (base_quant > 45);
}
void vp9_setup_in_frame_q_adj(VP9_COMP *cpi) {
VP9_COMMON *const cm = &cpi->common;
struct segmentation *const seg = &cm->seg;
// Make SURE use of floating point in this function is safe.
vp9_clear_system_state();
if (cm->frame_type == KEY_FRAME ||
cpi->refresh_alt_ref_frame ||
(cpi->refresh_golden_frame && !cpi->rc.is_src_frame_alt_ref)) {
int segment;
const int aq_strength = get_aq_c_strength(cm->base_qindex);
const int active_segments = aq_c_active_segments[aq_strength];
// Clear down the segment map.
vpx_memset(cpi->segmentation_map, 0, cm->mi_rows * cm->mi_cols);
// Clear down the complexity map used for rd.
vpx_memset(cpi->complexity_map, 0, cm->mi_rows * cm->mi_cols);
vp9_clearall_segfeatures(seg);
// Segmentation only makes sense if the target bits per SB is above a
// threshold. Below this the overheads will usually outweigh any benefit.
if (cpi->rc.sb64_target_rate < 256) {
vp9_disable_segmentation(seg);
return;
}
vp9_enable_segmentation(seg);
// Select delta coding method.
seg->abs_delta = SEGMENT_DELTADATA;
// Segment 0 "Q" feature is disabled so it defaults to the baseline Q.
vp9_disable_segfeature(seg, 0, SEG_LVL_ALT_Q);
// Use some of the segments for in frame Q adjustment.
for (segment = 1; segment < active_segments; ++segment) {
int qindex_delta =
vp9_compute_qdelta_by_rate(&cpi->rc, cm->frame_type, cm->base_qindex,
aq_c_q_adj_factor[aq_strength][segment]);
// For AQ complexity mode, we dont allow Q0 in a segment if the base
// Q is not 0. Q0 (lossless) implies 4x4 only and in AQ mode 2 a segment
// Q delta is sometimes applied without going back around the rd loop.
// This could lead to an illegal combination of partition size and q.
if ((cm->base_qindex != 0) && ((cm->base_qindex + qindex_delta) == 0)) {
qindex_delta = -cm->base_qindex + 1;
}
if ((cm->base_qindex + qindex_delta) > 0) {
vp9_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
vp9_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
}
}
}
}
// Select a segment for the current SB64 block.
// The choice of segment for a block depends on the ratio of the projected
// bits for the block vs a target average.
// An "aq_strength" value determines how many segments are supported,
// the set of transition points to use and the extent of the quantizer
// adjustment for each segment (configured in vp9_setup_in_frame_q_adj()).
void vp9_select_in_frame_q_segment(VP9_COMP *cpi,
int mi_row, int mi_col,
int output_enabled, int projected_rate) {
VP9_COMMON *const cm = &cpi->common;
const int mi_offset = mi_row * cm->mi_cols + mi_col;
const int bw = num_8x8_blocks_wide_lookup[BLOCK_64X64];
const int bh = num_8x8_blocks_high_lookup[BLOCK_64X64];
const int xmis = MIN(cm->mi_cols - mi_col, bw);
const int ymis = MIN(cm->mi_rows - mi_row, bh);
int complexity_metric = 64;
int x, y;
unsigned char segment;
if (!output_enabled) {
segment = 0;
} else {
// Rate depends on fraction of a SB64 in frame (xmis * ymis / bw * bh).
// It is converted to bits * 256 units.
const int target_rate = (cpi->rc.sb64_target_rate * xmis * ymis * 256) /
(bw * bh);
const int aq_strength = get_aq_c_strength(cm->base_qindex);
const int active_segments = aq_c_active_segments[aq_strength];
// The number of segments considered and the transition points used to
// select them is determined by the "aq_strength" value.
// Currently this loop only supports segments that reduce Q (i.e. where
// there is undershoot.
// The loop counts down towards segment 0 which is the default segment
// with no Q adjustment.
segment = active_segments - 1;
while (segment > 0) {
if (projected_rate <
(target_rate * aq_c_transitions[aq_strength][segment])) {
break;
}
--segment;
}
if (target_rate > 0) {
complexity_metric =
clamp((int)((projected_rate * 64) / target_rate), 16, 255);
}
}
// Fill in the entires in the segment map corresponding to this SB64.
for (y = 0; y < ymis; y++) {
for (x = 0; x < xmis; x++) {
cpi->segmentation_map[mi_offset + y * cm->mi_cols + x] = segment;
cpi->complexity_map[mi_offset + y * cm->mi_cols + x] =
(unsigned char)complexity_metric;
}
}
}