// 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;
}
static int estimate_bits_at_q(int frame_kind, int q, int mbs,
double correction_factor) {
const int bpm = (int)(vp9_rc_bits_per_mb(frame_kind, q, correction_factor));
// Attempt to retain reasonable accuracy without overflow. The cutoff is
// chosen such that the maximum product of Bpm and MBs fits 31 bits. The
// largest Bpm takes 20 bits.
return (mbs > (1 << 11)) ? (bpm >> BPER_MB_NORMBITS) * mbs
: (bpm * mbs) >> BPER_MB_NORMBITS;
}
