ref: 343acaa8f2233acfe427a8e3557efa7bae092d77
dir: /vp9/encoder/vp9_aq_cyclicrefresh.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/encoder/vp9_aq_cyclicrefresh.h"
#include "vp9/common/vp9_seg_common.h"
#include "vp9/encoder/vp9_ratectrl.h"
#include "vp9/encoder/vp9_segmentation.h"
struct CYCLIC_REFRESH {
// Percentage of super-blocks per frame that are targeted as candidates
// for cyclic refresh.
int max_sbs_perframe;
// Maximum q-delta as percentage of base q.
int max_qdelta_perc;
// Block size below which we don't apply cyclic refresh.
BLOCK_SIZE min_block_size;
// Superblock starting index for cycling through the frame.
int sb_index;
// Controls how long a block will need to wait to be refreshed again.
int time_for_refresh;
// Actual number of (8x8) blocks that were applied delta-q (segment 1).
int num_seg_blocks;
// Actual encoding bits for segment 1.
int actual_seg_bits;
// RD mult. parameters for segment 1.
int rdmult;
// Cyclic refresh map.
signed char *map;
// Projected rate and distortion for the current superblock.
int64_t projected_rate_sb;
int64_t projected_dist_sb;
// Thresholds applied to projected rate/distortion of the superblock.
int64_t thresh_rate_sb;
int64_t thresh_dist_sb;
};
CYCLIC_REFRESH *vp9_cyclic_refresh_alloc(int mi_rows, int mi_cols) {
CYCLIC_REFRESH *const cr = vpx_calloc(1, sizeof(*cr));
if (cr == NULL)
return NULL;
cr->map = vpx_calloc(mi_rows * mi_cols, sizeof(*cr->map));
if (cr->map == NULL) {
vpx_free(cr);
return NULL;
}
return cr;
}
void vp9_cyclic_refresh_free(CYCLIC_REFRESH *cr) {
vpx_free(cr->map);
vpx_free(cr);
}
// Check if we should turn off cyclic refresh based on bitrate condition.
static int apply_cyclic_refresh_bitrate(const VP9_COMMON *cm,
const RATE_CONTROL *rc) {
// Turn off cyclic refresh if bits available per frame is not sufficiently
// larger than bit cost of segmentation. Segment map bit cost should scale
// with number of seg blocks, so compare available bits to number of blocks.
// Average bits available per frame = avg_frame_bandwidth
// Number of (8x8) blocks in frame = mi_rows * mi_cols;
const float factor = 0.5;
const int number_blocks = cm->mi_rows * cm->mi_cols;
// The condition below corresponds to turning off at target bitrates:
// ~24kbps for CIF, 72kbps for VGA (at 30fps).
// Also turn off at very small frame sizes, to avoid too large fraction of
// superblocks to be refreshed per frame. Threshold below is less than QCIF.
if (rc->avg_frame_bandwidth < factor * number_blocks ||
number_blocks / 64 < 5)
return 0;
else
return 1;
}
// Check if this coding block, of size bsize, should be considered for refresh
// (lower-qp coding). Decision can be based on various factors, such as
// size of the coding block (i.e., below min_block size rejected), coding
// mode, and rate/distortion.
static int candidate_refresh_aq(const CYCLIC_REFRESH *cr,
const MB_MODE_INFO *mbmi,
BLOCK_SIZE bsize, int use_rd) {
if (use_rd) {
// If projected rate is below the thresh_rate (well below target,
// so undershoot expected), accept it for lower-qp coding.
if (cr->projected_rate_sb < cr->thresh_rate_sb)
return 1;
// Otherwise, reject the block for lower-qp coding if any of the following:
// 1) prediction block size is below min_block_size
// 2) mode is non-zero mv and projected distortion is above thresh_dist
// 3) mode is an intra-mode (we may want to allow some of this under
// another thresh_dist)
else if (bsize < cr->min_block_size ||
(mbmi->mv[0].as_int != 0 &&
cr->projected_dist_sb > cr->thresh_dist_sb) ||
!is_inter_block(mbmi))
return 0;
else
return 1;
} else {
// Rate/distortion not used for update.
if (bsize < cr->min_block_size ||
mbmi->mv[0].as_int != 0 ||
!is_inter_block(mbmi))
return 0;
else
return 1;
}
}
// Prior to coding a given prediction block, of size bsize at (mi_row, mi_col),
// check if we should reset the segment_id, and update the cyclic_refresh map
// and segmentation map.
void vp9_cyclic_refresh_update_segment(VP9_COMP *const cpi,
MB_MODE_INFO *const mbmi,
int mi_row, int mi_col,
BLOCK_SIZE bsize, int use_rd) {
const VP9_COMMON *const cm = &cpi->common;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
const int bw = num_8x8_blocks_wide_lookup[bsize];
const int bh = num_8x8_blocks_high_lookup[bsize];
const int xmis = MIN(cm->mi_cols - mi_col, bw);
const int ymis = MIN(cm->mi_rows - mi_row, bh);
const int block_index = mi_row * cm->mi_cols + mi_col;
const int refresh_this_block = cpi->mb.in_static_area ||
candidate_refresh_aq(cr, mbmi, bsize, use_rd);
// Default is to not update the refresh map.
int new_map_value = cr->map[block_index];
int x = 0; int y = 0;
// Check if we should reset the segment_id for this block.
if (mbmi->segment_id > 0 && !refresh_this_block)
mbmi->segment_id = 0;
// Update the cyclic refresh map, to be used for setting segmentation map
// for the next frame. If the block will be refreshed this frame, mark it
// as clean. The magnitude of the -ve influences how long before we consider
// it for refresh again.
if (mbmi->segment_id == 1) {
new_map_value = -cr->time_for_refresh;
} else if (refresh_this_block) {
// Else if it is accepted as candidate for refresh, and has not already
// been refreshed (marked as 1) then mark it as a candidate for cleanup
// for future time (marked as 0), otherwise don't update it.
if (cr->map[block_index] == 1)
new_map_value = 0;
} else {
// Leave it marked as block that is not candidate for refresh.
new_map_value = 1;
}
// Update entries in the cyclic refresh map with new_map_value, and
// copy mbmi->segment_id into global segmentation map.
for (y = 0; y < ymis; y++)
for (x = 0; x < xmis; x++) {
cr->map[block_index + y * cm->mi_cols + x] = new_map_value;
cpi->segmentation_map[block_index + y * cm->mi_cols + x] =
mbmi->segment_id;
}
// Keep track of actual number (in units of 8x8) of blocks in segment 1 used
// for encoding this frame.
if (mbmi->segment_id)
cr->num_seg_blocks += xmis * ymis;
}
// Setup cyclic background refresh: set delta q and segmentation map.
void vp9_cyclic_refresh_setup(VP9_COMP *const cpi) {
VP9_COMMON *const cm = &cpi->common;
const RATE_CONTROL *const rc = &cpi->rc;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
struct segmentation *const seg = &cm->seg;
unsigned char *const seg_map = cpi->segmentation_map;
const int apply_cyclic_refresh = apply_cyclic_refresh_bitrate(cm, rc);
// Don't apply refresh on key frame or enhancement layer frames.
if (!apply_cyclic_refresh ||
(cm->frame_type == KEY_FRAME) ||
(cpi->svc.temporal_layer_id > 0)) {
// Set segmentation map to 0 and disable.
vpx_memset(seg_map, 0, cm->mi_rows * cm->mi_cols);
vp9_disable_segmentation(&cm->seg);
if (cm->frame_type == KEY_FRAME)
cr->sb_index = 0;
return;
} else {
int qindex_delta = 0;
int i, block_count, bl_index, sb_rows, sb_cols, sbs_in_frame;
int xmis, ymis, x, y, qindex2;
// Rate target ratio to set q delta.
const float rate_ratio_qdelta = 2.0;
const double q = vp9_convert_qindex_to_q(cm->base_qindex, cm->bit_depth);
vp9_clear_system_state();
// Some of these parameters may be set via codec-control function later.
cr->max_sbs_perframe = 10;
cr->max_qdelta_perc = 50;
cr->min_block_size = BLOCK_8X8;
cr->time_for_refresh = 1;
// Set rate threshold to some fraction of target (and scaled by 256).
cr->thresh_rate_sb = (rc->sb64_target_rate * 256) >> 2;
// Distortion threshold, quadratic in Q, scale factor to be adjusted.
cr->thresh_dist_sb = 8 * (int)(q * q);
if (cpi->sf.use_nonrd_pick_mode) {
// May want to be more conservative with thresholds in non-rd mode for now
// as rate/distortion are derived from model based on prediction residual.
cr->thresh_rate_sb = (rc->sb64_target_rate * 256) >> 3;
cr->thresh_dist_sb = 4 * (int)(q * q);
}
cr->num_seg_blocks = 0;
// Set up segmentation.
// Clear down the segment map.
vpx_memset(seg_map, 0, cm->mi_rows * cm->mi_cols);
vp9_enable_segmentation(&cm->seg);
vp9_clearall_segfeatures(seg);
// Select delta coding method.
seg->abs_delta = SEGMENT_DELTADATA;
// Note: setting temporal_update has no effect, as the seg-map coding method
// (temporal or spatial) is determined in vp9_choose_segmap_coding_method(),
// based on the coding cost of each method. For error_resilient mode on the
// last_frame_seg_map is set to 0, so if temporal coding is used, it is
// relative to 0 previous map.
// seg->temporal_update = 0;
// Segment 0 "Q" feature is disabled so it defaults to the baseline Q.
vp9_disable_segfeature(seg, 0, SEG_LVL_ALT_Q);
// Use segment 1 for in-frame Q adjustment.
vp9_enable_segfeature(seg, 1, SEG_LVL_ALT_Q);
// Set the q delta for segment 1.
qindex_delta = vp9_compute_qdelta_by_rate(rc, cm->frame_type,
cm->base_qindex,
rate_ratio_qdelta,
cm->bit_depth);
// TODO(marpan): Incorporate the actual-vs-target rate over/undershoot from
// previous encoded frame.
if (-qindex_delta > cr->max_qdelta_perc * cm->base_qindex / 100)
qindex_delta = -cr->max_qdelta_perc * cm->base_qindex / 100;
// Compute rd-mult for segment 1.
qindex2 = clamp(cm->base_qindex + cm->y_dc_delta_q + qindex_delta, 0, MAXQ);
cr->rdmult = vp9_compute_rd_mult(cpi, qindex2);
vp9_set_segdata(seg, 1, SEG_LVL_ALT_Q, qindex_delta);
sb_cols = (cm->mi_cols + MI_BLOCK_SIZE - 1) / MI_BLOCK_SIZE;
sb_rows = (cm->mi_rows + MI_BLOCK_SIZE - 1) / MI_BLOCK_SIZE;
sbs_in_frame = sb_cols * sb_rows;
// Number of target superblocks to get the q delta (segment 1).
block_count = cr->max_sbs_perframe * sbs_in_frame / 100;
// Set the segmentation map: cycle through the superblocks, starting at
// cr->mb_index, and stopping when either block_count blocks have been found
// to be refreshed, or we have passed through whole frame.
assert(cr->sb_index < sbs_in_frame);
i = cr->sb_index;
do {
int sum_map = 0;
// Get the mi_row/mi_col corresponding to superblock index i.
int sb_row_index = (i / sb_cols);
int sb_col_index = i - sb_row_index * sb_cols;
int mi_row = sb_row_index * MI_BLOCK_SIZE;
int mi_col = sb_col_index * MI_BLOCK_SIZE;
assert(mi_row >= 0 && mi_row < cm->mi_rows);
assert(mi_col >= 0 && mi_col < cm->mi_cols);
bl_index = mi_row * cm->mi_cols + mi_col;
// Loop through all 8x8 blocks in superblock and update map.
xmis = MIN(cm->mi_cols - mi_col,
num_8x8_blocks_wide_lookup[BLOCK_64X64]);
ymis = MIN(cm->mi_rows - mi_row,
num_8x8_blocks_high_lookup[BLOCK_64X64]);
for (y = 0; y < ymis; y++) {
for (x = 0; x < xmis; x++) {
const int bl_index2 = bl_index + y * cm->mi_cols + x;
// If the block is as a candidate for clean up then mark it
// for possible boost/refresh (segment 1). The segment id may get
// reset to 0 later if block gets coded anything other than ZEROMV.
if (cr->map[bl_index2] == 0) {
seg_map[bl_index2] = 1;
sum_map++;
} else if (cr->map[bl_index2] < 0) {
cr->map[bl_index2]++;
}
}
}
// Enforce constant segment over superblock.
// If segment is partial over superblock, reset to either all 1 or 0.
if (sum_map > 0 && sum_map < xmis * ymis) {
const int new_value = (sum_map >= xmis * ymis / 2);
for (y = 0; y < ymis; y++)
for (x = 0; x < xmis; x++)
seg_map[bl_index + y * cm->mi_cols + x] = new_value;
}
i++;
if (i == sbs_in_frame) {
i = 0;
}
if (sum_map >= xmis * ymis /2)
block_count--;
} while (block_count && i != cr->sb_index);
cr->sb_index = i;
}
}
void vp9_cyclic_refresh_set_rate_and_dist_sb(CYCLIC_REFRESH *cr,
int64_t rate_sb, int64_t dist_sb) {
cr->projected_rate_sb = rate_sb;
cr->projected_dist_sb = dist_sb;
}
int vp9_cyclic_refresh_get_rdmult(const CYCLIC_REFRESH *cr) {
return cr->rdmult;
}