aom/vp9/encoder/vp9_aq_cyclicrefresh.c

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C
Исходник Обычный вид История

/*
* 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 blocks per frame that are targeted as candidates
// for cyclic refresh.
int percent_refresh;
// Maximum q-delta as percentage of base q.
int max_qdelta_perc;
// Superblock starting index for cycling through the frame.
int sb_index;
// Controls how long block will need to wait to be refreshed again, in
// excess of the cycle time, i.e., in the case of all zero motion, block
// will be refreshed every (100/percent_refresh + time_for_refresh) frames.
int time_for_refresh;
// Target number of (8x8) blocks that are set for delta-q.
int target_num_seg_blocks;
// Actual number of (8x8) blocks that were applied delta-q.
int actual_num_seg1_blocks;
int actual_num_seg2_blocks;
// RD mult. parameters for segment 1.
int rdmult;
// Cyclic refresh map.
signed char *map;
// Thresholds applied to the projected rate/distortion of the coding block,
// when deciding whether block should be refreshed.
int64_t thresh_rate_sb;
int64_t thresh_dist_sb;
// Threshold applied to the motion vector (in units of 1/8 pel) of the
// coding block, when deciding whether block should be refreshed.
int16_t motion_thresh;
// Rate target ratio to set q delta.
double rate_ratio_qdelta;
double low_content_avg;
int qindex_delta_seg1;
int qindex_delta_seg2;
};
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 = 0.25;
const int number_blocks = cm->mi_rows * cm->mi_cols;
// The condition below corresponds to turning off at target bitrates:
// (at 30fps), ~12kbps for CIF, 36kbps for VGA, 100kps for HD/720p.
// 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,
int64_t rate,
int64_t dist,
int bsize) {
MV mv = mbmi->mv[0].as_mv;
// Reject the block for lower-qp coding if projected distortion
// is above the threshold, and any of the following is true:
// 1) mode uses large mv
// 2) mode is an intra-mode
// Otherwise accept for refresh.
if (dist > cr->thresh_dist_sb &&
(mv.row > cr->motion_thresh || mv.row < -cr->motion_thresh ||
mv.col > cr->motion_thresh || mv.col < -cr->motion_thresh ||
!is_inter_block(mbmi)))
return CR_SEGMENT_ID_BASE;
else if (bsize >= BLOCK_16X16 &&
rate < cr->thresh_rate_sb &&
is_inter_block(mbmi) &&
mbmi->mv[0].as_int == 0)
// More aggressive delta-q for bigger blocks with zero motion.
return CR_SEGMENT_ID_BOOST2;
else
return CR_SEGMENT_ID_BOOST1;
}
// Compute delta-q for the segment.
static int compute_deltaq(const VP9_COMP *cpi, int q, double rate_factor) {
const CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
const RATE_CONTROL *const rc = &cpi->rc;
int deltaq = vp9_compute_qdelta_by_rate(rc, cpi->common.frame_type,
q, rate_factor,
cpi->common.bit_depth);
if ((-deltaq) > cr->max_qdelta_perc * q / 100) {
deltaq = -cr->max_qdelta_perc * q / 100;
}
return deltaq;
}
// For the just encoded frame, estimate the bits, incorporating the delta-q
// from non-base segment. For now ignore effect of multiple segments
// (with different delta-q). Note this function is called in the postencode
// (called from rc_update_rate_correction_factors()).
int vp9_cyclic_refresh_estimate_bits_at_q(const VP9_COMP *cpi,
double correction_factor) {
const VP9_COMMON *const cm = &cpi->common;
const CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
int estimated_bits;
int mbs = cm->MBs;
int num8x8bl = mbs << 2;
// Weight for non-base segments: use actual number of blocks refreshed in
// previous/just encoded frame. Note number of blocks here is in 8x8 units.
double weight_segment1 = (double)cr->actual_num_seg1_blocks / num8x8bl;
double weight_segment2 = (double)cr->actual_num_seg2_blocks / num8x8bl;
// Take segment weighted average for estimated bits.
estimated_bits = (int)((1.0 - weight_segment1 - weight_segment2) *
vp9_estimate_bits_at_q(cm->frame_type, cm->base_qindex, mbs,
correction_factor, cm->bit_depth) +
weight_segment1 *
vp9_estimate_bits_at_q(cm->frame_type,
cm->base_qindex + cr->qindex_delta_seg1, mbs,
correction_factor, cm->bit_depth) +
weight_segment2 *
vp9_estimate_bits_at_q(cm->frame_type,
cm->base_qindex + cr->qindex_delta_seg2, mbs,
correction_factor, cm->bit_depth));
return estimated_bits;
}
// Prior to encoding the frame, estimate the bits per mb, for a given q = i and
// a corresponding delta-q (for segment 1). This function is called in the
// rc_regulate_q() to set the base qp index.
// Note: the segment map is set to either 0/CR_SEGMENT_ID_BASE (no refresh) or
// to 1/CR_SEGMENT_ID_BOOST1 (refresh) for each superblock, prior to encoding.
int vp9_cyclic_refresh_rc_bits_per_mb(const VP9_COMP *cpi, int i,
double correction_factor) {
const VP9_COMMON *const cm = &cpi->common;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
int bits_per_mb;
int num8x8bl = cm->MBs << 2;
// Weight for segment prior to encoding: take the average of the target
// number for the frame to be encoded and the actual from the previous frame.
double weight_segment = (double)((cr->target_num_seg_blocks +
cr->actual_num_seg1_blocks + cr->actual_num_seg2_blocks) >> 1) /
num8x8bl;
// Compute delta-q corresponding to qindex i.
int deltaq = compute_deltaq(cpi, i, cr->rate_ratio_qdelta);
// Take segment weighted average for bits per mb.
bits_per_mb = (int)((1.0 - weight_segment) *
vp9_rc_bits_per_mb(cm->frame_type, i, correction_factor, cm->bit_depth) +
weight_segment *
vp9_rc_bits_per_mb(cm->frame_type, i + deltaq, correction_factor,
cm->bit_depth));
return bits_per_mb;
}
// 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,
int64_t rate,
int64_t dist,
int skip) {
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 = candidate_refresh_aq(cr, mbmi, rate, dist,
bsize);
// Default is to not update the refresh map.
int new_map_value = cr->map[block_index];
int x = 0; int y = 0;
// If this block is labeled for refresh, check if we should reset the
// segment_id.
if (cyclic_refresh_segment_id_boosted(mbmi->segment_id)) {
mbmi->segment_id = refresh_this_block;
// Reset segment_id if will be skipped.
if (skip)
mbmi->segment_id = CR_SEGMENT_ID_BASE;
}
// 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 (cyclic_refresh_segment_id_boosted(mbmi->segment_id)) {
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;
}
}
// Update the actual number of blocks that were applied the segment delta q.
void vp9_cyclic_refresh_postencode(VP9_COMP *const cpi) {
VP9_COMMON *const cm = &cpi->common;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
unsigned char *const seg_map = cpi->segmentation_map;
int mi_row, mi_col;
cr->actual_num_seg1_blocks = 0;
cr->actual_num_seg2_blocks = 0;
for (mi_row = 0; mi_row < cm->mi_rows; mi_row++)
for (mi_col = 0; mi_col < cm->mi_cols; mi_col++) {
if (cyclic_refresh_segment_id(
seg_map[mi_row * cm->mi_cols + mi_col]) == CR_SEGMENT_ID_BOOST1)
cr->actual_num_seg1_blocks++;
else if (cyclic_refresh_segment_id(
seg_map[mi_row * cm->mi_cols + mi_col]) == CR_SEGMENT_ID_BOOST2)
cr->actual_num_seg2_blocks++;
}
}
// Set golden frame update interval, for non-svc 1 pass CBR mode.
void vp9_cyclic_refresh_set_golden_update(VP9_COMP *const cpi) {
RATE_CONTROL *const rc = &cpi->rc;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
// Set minimum gf_interval for GF update to a multiple (== 2) of refresh
// period. Depending on past encoding stats, GF flag may be reset and update
// may not occur until next baseline_gf_interval.
if (cr->percent_refresh > 0)
rc->baseline_gf_interval = 2 * (100 / cr->percent_refresh);
else
rc->baseline_gf_interval = 20;
}
// Update some encoding stats (from the just encoded frame), and if the golden
// reference is to be updated check if we should NOT update the golden ref.
void vp9_cyclic_refresh_check_golden_update(VP9_COMP *const cpi) {
VP9_COMMON *const cm = &cpi->common;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
int mi_row, mi_col;
double fraction_low = 0.0;
int low_content_frame = 0;
for (mi_row = 0; mi_row < cm->mi_rows; mi_row++)
for (mi_col = 0; mi_col < cm->mi_cols; mi_col++) {
if (cr->map[mi_row * cm->mi_cols + mi_col] < 1)
low_content_frame++;
}
fraction_low =
(double)low_content_frame / (cm->mi_rows * cm->mi_cols);
// Update average.
cr->low_content_avg = (fraction_low + 3 * cr->low_content_avg) / 4;
if (cpi->refresh_golden_frame == 1) {
// Don't update golden reference if the amount of low_content for the
// current encoded frame is small, or if the recursive average of the
// low_content over the update interval window falls below threshold.
if (fraction_low < 0.8 || cr->low_content_avg < 0.7)
cpi->refresh_golden_frame = 0;
// Reset for next internal.
cr->low_content_avg = fraction_low;
}
}
// Update the segmentation map, and related quantities: cyclic refresh map,
// refresh sb_index, and target number of blocks to be refreshed.
// The map is set to either 0/CR_SEGMENT_ID_BASE (no refresh) or to
// 1/CR_SEGMENT_ID_BOOST1 (refresh) for each superblock.
// Blocks labeled as BOOST1 may later get set to BOOST2 (during the
// encoding of the superblock).
void vp9_cyclic_refresh_update_map(VP9_COMP *const cpi) {
VP9_COMMON *const cm = &cpi->common;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
unsigned char *const seg_map = cpi->segmentation_map;
int i, block_count, bl_index, sb_rows, sb_cols, sbs_in_frame;
int xmis, ymis, x, y;
vpx_memset(seg_map, CR_SEGMENT_ID_BASE, cm->mi_rows * cm->mi_cols);
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 blocks to get the q delta (segment 1).
block_count = cr->percent_refresh * cm->mi_rows * cm->mi_cols / 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;
cr->target_num_seg_blocks = 0;
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) {
sum_map++;
} else if (cr->map[bl_index2] < 0) {
cr->map[bl_index2]++;
}
}
}
// Enforce constant segment over superblock.
// If segment is at least half of superblock, set to 1.
if (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] = CR_SEGMENT_ID_BOOST1;
}
cr->target_num_seg_blocks += xmis * ymis;
}
i++;
if (i == sbs_in_frame) {
i = 0;
}
} while (cr->target_num_seg_blocks < block_count && i != cr->sb_index);
cr->sb_index = i;
}
// Set/update global/frame level cyclic refresh parameters.
void vp9_cyclic_refresh_update_parameters(VP9_COMP *const cpi) {
const RATE_CONTROL *const rc = &cpi->rc;
CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
cr->percent_refresh = 10;
// Use larger delta-qp (increase rate_ratio_qdelta) for first few (~4)
// periods of the refresh cycle, after a key frame. This corresponds to ~40
// frames with cr->percent_refresh = 10.
if (rc->frames_since_key < 40)
cr->rate_ratio_qdelta = 3.0;
else
cr->rate_ratio_qdelta = 2.0;
}
// 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;
const int apply_cyclic_refresh = apply_cyclic_refresh_bitrate(cm, rc);
if (cm->current_video_frame == 0)
cr->low_content_avg = 0.0;
// 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) ||
(cpi->svc.spatial_layer_id > 0)) {
// Set segmentation map to 0 and disable.
unsigned char *const seg_map = cpi->segmentation_map;
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 qindex2;
const double q = vp9_convert_qindex_to_q(cm->base_qindex, cm->bit_depth);
vp9_clear_system_state();
cr->max_qdelta_perc = 50;
cr->time_for_refresh = 0;
// Set rate threshold to some multiple (set to 2 for now) of the target
// rate (target is given by sb64_target_rate and scaled by 256).
cr->thresh_rate_sb = ((int64_t)(rc->sb64_target_rate) << 8) << 2;
// Distortion threshold, quadratic in Q, scale factor to be adjusted.
// q will not exceed 457, so (q * q) is within 32bit; see:
// vp9_convert_qindex_to_q(), vp9_ac_quant(), ac_qlookup*[].
cr->thresh_dist_sb = ((int64_t)(q * q)) << 2;
cr->motion_thresh = 32;
// Set up segmentation.
// Clear down the segment map.
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 BASE "Q" feature is disabled so it defaults to the baseline Q.
vp9_disable_segfeature(seg, CR_SEGMENT_ID_BASE, SEG_LVL_ALT_Q);
// Use segment BOOST1 for in-frame Q adjustment.
vp9_enable_segfeature(seg, CR_SEGMENT_ID_BOOST1, SEG_LVL_ALT_Q);
// Use segment BOOST2 for more aggressive in-frame Q adjustment.
vp9_enable_segfeature(seg, CR_SEGMENT_ID_BOOST2, SEG_LVL_ALT_Q);
// Set the q delta for segment BOOST1.
qindex_delta = compute_deltaq(cpi, cm->base_qindex, cr->rate_ratio_qdelta);
cr->qindex_delta_seg1 = qindex_delta;
// Compute rd-mult for segment BOOST1.
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, CR_SEGMENT_ID_BOOST1, SEG_LVL_ALT_Q, qindex_delta);
// Set a more aggressive (higher) q delta for segment BOOST2.
qindex_delta = compute_deltaq(cpi, cm->base_qindex,
MIN(CR_MAX_RATE_TARGET_RATIO,
CR_BOOST2_FAC * cr->rate_ratio_qdelta));
cr->qindex_delta_seg2 = qindex_delta;
vp9_set_segdata(seg, CR_SEGMENT_ID_BOOST2, SEG_LVL_ALT_Q, qindex_delta);
// Update the segmentation and refresh map.
vp9_cyclic_refresh_update_map(cpi);
}
}
int vp9_cyclic_refresh_get_rdmult(const CYCLIC_REFRESH *cr) {
return cr->rdmult;
}