// 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.
int target_refresh = cr->percent_refresh * cm->mi_rows * cm->mi_cols / 100;
double weight_segment =
(double)((target_refresh + 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;
}
// Setup cyclic background refresh: set delta q and segmentation map.
void av1_cyclic_refresh_setup(AV1_COMP *const cpi) {
AV1_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) {
// Set segmentation map to 0 and disable.
unsigned char *const seg_map = cpi->segmentation_map;
memset(seg_map, 0, cm->mi_rows * cm->mi_cols);
av1_disable_segmentation(&cm->seg);
if (cm->frame_type == KEY_FRAME) {
memset(cr->last_coded_q_map, MAXQ,
cm->mi_rows * cm->mi_cols * sizeof(*cr->last_coded_q_map));
cr->sb_index = 0;
}
return;
} else {
int qindex_delta = 0;
int qindex2;
const double q = av1_convert_qindex_to_q(cm->base_qindex, cm->bit_depth);
aom_clear_system_state();
// 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:
// av1_convert_qindex_to_q(), av1_ac_quant(), ac_qlookup*[].
cr->thresh_dist_sb = ((int64_t)(q * q)) << 2;
// Set up segmentation.
// Clear down the segment map.
av1_enable_segmentation(&cm->seg);
av1_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
// av1_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.
av1_disable_segfeature(seg, CR_SEGMENT_ID_BASE, SEG_LVL_ALT_Q);
// Use segment BOOST1 for in-frame Q adjustment.
av1_enable_segfeature(seg, CR_SEGMENT_ID_BOOST1, SEG_LVL_ALT_Q);
// Use segment BOOST2 for more aggressive in-frame Q adjustment.
av1_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[1] = qindex_delta;
// Compute rd-mult for segment BOOST1.
qindex2 = clamp(cm->base_qindex + cm->y_dc_delta_q + qindex_delta, 0, MAXQ);
cr->rdmult = av1_compute_rd_mult(cpi, qindex2);
av1_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,
AOMMIN(CR_MAX_RATE_TARGET_RATIO,
0.1 * cr->rate_boost_fac * cr->rate_ratio_qdelta));
cr->qindex_delta[2] = qindex_delta;
av1_set_segdata(seg, CR_SEGMENT_ID_BOOST2, SEG_LVL_ALT_Q, qindex_delta);
// Update the segmentation and refresh map.
cyclic_refresh_update_map(cpi);
}
}