ref: 9a03154f4657f62ef21901a9117910eb569626b9
dir: /vp9/encoder/vp9_ratectrl.c/
/*
* Copyright (c) 2010 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 <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <assert.h>
#include <math.h>
#include "vp9/common/vp9_alloccommon.h"
#include "vp9/common/vp9_common.h"
#include "vp9/encoder/vp9_ratectrl.h"
#include "vp9/common/vp9_entropymode.h"
#include "vpx_mem/vpx_mem.h"
#include "vp9/common/vp9_systemdependent.h"
#include "vp9/encoder/vp9_encodemv.h"
#include "vp9/common/vp9_quant_common.h"
#include "vp9/common/vp9_seg_common.h"
#define MIN_BPB_FACTOR 0.005
#define MAX_BPB_FACTOR 50
// Bits Per MB at different Q (Multiplied by 512)
#define BPER_MB_NORMBITS 9
static const unsigned int prior_key_frame_weight[KEY_FRAME_CONTEXT] =
{ 1, 2, 3, 4, 5 };
// These functions use formulaic calculations to make playing with the
// quantizer tables easier. If necessary they can be replaced by lookup
// tables if and when things settle down in the experimental bitstream
double vp9_convert_qindex_to_q(int qindex) {
// Convert the index to a real Q value (scaled down to match old Q values)
return vp9_ac_quant(qindex, 0) / 4.0;
}
int vp9_gfboost_qadjust(int qindex) {
const double q = vp9_convert_qindex_to_q(qindex);
return (int)((0.00000828 * q * q * q) +
(-0.0055 * q * q) +
(1.32 * q) + 79.3);
}
static int kfboost_qadjust(int qindex) {
const double q = vp9_convert_qindex_to_q(qindex);
return (int)((0.00000973 * q * q * q) +
(-0.00613 * q * q) +
(1.316 * q) + 121.2);
}
int vp9_bits_per_mb(FRAME_TYPE frame_type, int qindex,
double correction_factor) {
const double q = vp9_convert_qindex_to_q(qindex);
int enumerator = frame_type == KEY_FRAME ? 3300000 : 2250000;
// q based adjustment to baseline enumerator
enumerator += (int)(enumerator * q) >> 12;
return (int)(0.5 + (enumerator * correction_factor / q));
}
void vp9_save_coding_context(VP9_COMP *cpi) {
CODING_CONTEXT *const cc = &cpi->coding_context;
VP9_COMMON *cm = &cpi->common;
// Stores a snapshot of key state variables which can subsequently be
// restored with a call to vp9_restore_coding_context. These functions are
// intended for use in a re-code loop in vp9_compress_frame where the
// quantizer value is adjusted between loop iterations.
vp9_copy(cc->nmvjointcost, cpi->mb.nmvjointcost);
vp9_copy(cc->nmvcosts, cpi->mb.nmvcosts);
vp9_copy(cc->nmvcosts_hp, cpi->mb.nmvcosts_hp);
vp9_copy(cc->segment_pred_probs, cm->seg.pred_probs);
vpx_memcpy(cpi->coding_context.last_frame_seg_map_copy,
cm->last_frame_seg_map, (cm->mi_rows * cm->mi_cols));
vp9_copy(cc->last_ref_lf_deltas, cm->lf.last_ref_deltas);
vp9_copy(cc->last_mode_lf_deltas, cm->lf.last_mode_deltas);
cc->fc = cm->fc;
}
void vp9_restore_coding_context(VP9_COMP *cpi) {
CODING_CONTEXT *const cc = &cpi->coding_context;
VP9_COMMON *cm = &cpi->common;
// Restore key state variables to the snapshot state stored in the
// previous call to vp9_save_coding_context.
vp9_copy(cpi->mb.nmvjointcost, cc->nmvjointcost);
vp9_copy(cpi->mb.nmvcosts, cc->nmvcosts);
vp9_copy(cpi->mb.nmvcosts_hp, cc->nmvcosts_hp);
vp9_copy(cm->seg.pred_probs, cc->segment_pred_probs);
vpx_memcpy(cm->last_frame_seg_map,
cpi->coding_context.last_frame_seg_map_copy,
(cm->mi_rows * cm->mi_cols));
vp9_copy(cm->lf.last_ref_deltas, cc->last_ref_lf_deltas);
vp9_copy(cm->lf.last_mode_deltas, cc->last_mode_lf_deltas);
cm->fc = cc->fc;
}
void vp9_setup_key_frame(VP9_COMP *cpi) {
VP9_COMMON *cm = &cpi->common;
vp9_setup_past_independence(cm);
// interval before next GF
cpi->frames_till_gf_update_due = cpi->baseline_gf_interval;
/* All buffers are implicitly updated on key frames. */
cpi->refresh_golden_frame = 1;
cpi->refresh_alt_ref_frame = 1;
}
void vp9_setup_inter_frame(VP9_COMP *cpi) {
VP9_COMMON *cm = &cpi->common;
if (cm->error_resilient_mode || cm->intra_only)
vp9_setup_past_independence(cm);
assert(cm->frame_context_idx < NUM_FRAME_CONTEXTS);
cm->fc = cm->frame_contexts[cm->frame_context_idx];
}
static int estimate_bits_at_q(int frame_kind, int q, int mbs,
double correction_factor) {
const int bpm = (int)(vp9_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;
}
static void calc_iframe_target_size(VP9_COMP *cpi) {
// boost defaults to half second
int target;
// Clear down mmx registers to allow floating point in what follows
vp9_clear_system_state(); // __asm emms;
// New Two pass RC
target = cpi->per_frame_bandwidth;
if (cpi->oxcf.rc_max_intra_bitrate_pct) {
int max_rate = cpi->per_frame_bandwidth
* cpi->oxcf.rc_max_intra_bitrate_pct / 100;
if (target > max_rate)
target = max_rate;
}
cpi->this_frame_target = target;
}
// Do the best we can to define the parameters for the next GF based
// on what information we have available.
//
// In this experimental code only two pass is supported
// so we just use the interval determined in the two pass code.
static void calc_gf_params(VP9_COMP *cpi) {
// Set the gf interval
cpi->frames_till_gf_update_due = cpi->baseline_gf_interval;
}
static void calc_pframe_target_size(VP9_COMP *cpi) {
const int min_frame_target = MAX(cpi->min_frame_bandwidth,
cpi->av_per_frame_bandwidth >> 5);
if (cpi->refresh_alt_ref_frame) {
// Special alt reference frame case
// Per frame bit target for the alt ref frame
cpi->per_frame_bandwidth = cpi->twopass.gf_bits;
cpi->this_frame_target = cpi->per_frame_bandwidth;
} else {
// Normal frames (gf,and inter)
cpi->this_frame_target = cpi->per_frame_bandwidth;
}
// Check that the total sum of adjustments is not above the maximum allowed.
// That is, having allowed for the KF and GF penalties, we have not pushed
// the current inter-frame target too low. If the adjustment we apply here is
// not capable of recovering all the extra bits we have spent in the KF or GF,
// then the remainder will have to be recovered over a longer time span via
// other buffer / rate control mechanisms.
if (cpi->this_frame_target < min_frame_target)
cpi->this_frame_target = min_frame_target;
if (!cpi->refresh_alt_ref_frame)
// Note the baseline target data rate for this inter frame.
cpi->inter_frame_target = cpi->this_frame_target;
// Adjust target frame size for Golden Frames:
if (cpi->frames_till_gf_update_due == 0) {
const int q = (cpi->oxcf.fixed_q < 0) ? cpi->last_q[INTER_FRAME]
: cpi->oxcf.fixed_q;
cpi->refresh_golden_frame = 1;
calc_gf_params(cpi);
// If we are using alternate ref instead of gf then do not apply the boost
// It will instead be applied to the altref update
// Jims modified boost
if (!cpi->source_alt_ref_active) {
if (cpi->oxcf.fixed_q < 0) {
// The spend on the GF is defined in the two pass code
// for two pass encodes
cpi->this_frame_target = cpi->per_frame_bandwidth;
} else {
cpi->this_frame_target =
(estimate_bits_at_q(1, q, cpi->common.MBs, 1.0)
* cpi->last_boost) / 100;
}
} else {
// If there is an active ARF at this location use the minimum
// bits on this frame even if it is a constructed arf.
// The active maximum quantizer insures that an appropriate
// number of bits will be spent if needed for constructed ARFs.
cpi->this_frame_target = 0;
}
}
}
void vp9_update_rate_correction_factors(VP9_COMP *cpi, int damp_var) {
const int q = cpi->common.base_qindex;
int correction_factor = 100;
double rate_correction_factor;
double adjustment_limit;
int projected_size_based_on_q = 0;
// Clear down mmx registers to allow floating point in what follows
vp9_clear_system_state(); // __asm emms;
if (cpi->common.frame_type == KEY_FRAME) {
rate_correction_factor = cpi->key_frame_rate_correction_factor;
} else {
if (cpi->refresh_alt_ref_frame || cpi->refresh_golden_frame)
rate_correction_factor = cpi->gf_rate_correction_factor;
else
rate_correction_factor = cpi->rate_correction_factor;
}
// Work out how big we would have expected the frame to be at this Q given
// the current correction factor.
// Stay in double to avoid int overflow when values are large
projected_size_based_on_q = estimate_bits_at_q(cpi->common.frame_type, q,
cpi->common.MBs,
rate_correction_factor);
// Work out a size correction factor.
if (projected_size_based_on_q > 0)
correction_factor =
(100 * cpi->projected_frame_size) / projected_size_based_on_q;
// More heavily damped adjustment used if we have been oscillating either side
// of target.
switch (damp_var) {
case 0:
adjustment_limit = 0.75;
break;
case 1:
adjustment_limit = 0.375;
break;
case 2:
default:
adjustment_limit = 0.25;
break;
}
// if ( (correction_factor > 102) && (Q < cpi->active_worst_quality) )
if (correction_factor > 102) {
// We are not already at the worst allowable quality
correction_factor =
(int)(100.5 + ((correction_factor - 100) * adjustment_limit));
rate_correction_factor =
((rate_correction_factor * correction_factor) / 100);
// Keep rate_correction_factor within limits
if (rate_correction_factor > MAX_BPB_FACTOR)
rate_correction_factor = MAX_BPB_FACTOR;
} else if (correction_factor < 99) {
// We are not already at the best allowable quality
correction_factor =
(int)(100.5 - ((100 - correction_factor) * adjustment_limit));
rate_correction_factor =
((rate_correction_factor * correction_factor) / 100);
// Keep rate_correction_factor within limits
if (rate_correction_factor < MIN_BPB_FACTOR)
rate_correction_factor = MIN_BPB_FACTOR;
}
if (cpi->common.frame_type == KEY_FRAME) {
cpi->key_frame_rate_correction_factor = rate_correction_factor;
} else {
if (cpi->refresh_alt_ref_frame || cpi->refresh_golden_frame)
cpi->gf_rate_correction_factor = rate_correction_factor;
else
cpi->rate_correction_factor = rate_correction_factor;
}
}
int vp9_regulate_q(VP9_COMP *cpi, int target_bits_per_frame) {
int q = cpi->active_worst_quality;
int i;
int last_error = INT_MAX;
int target_bits_per_mb;
int bits_per_mb_at_this_q;
double correction_factor;
// Select the appropriate correction factor based upon type of frame.
if (cpi->common.frame_type == KEY_FRAME) {
correction_factor = cpi->key_frame_rate_correction_factor;
} else {
if (cpi->refresh_alt_ref_frame || cpi->refresh_golden_frame)
correction_factor = cpi->gf_rate_correction_factor;
else
correction_factor = cpi->rate_correction_factor;
}
// Calculate required scaling factor based on target frame size and size of
// frame produced using previous Q.
if (target_bits_per_frame >= (INT_MAX >> BPER_MB_NORMBITS))
target_bits_per_mb =
(target_bits_per_frame / cpi->common.MBs)
<< BPER_MB_NORMBITS; // Case where we would overflow int
else
target_bits_per_mb =
(target_bits_per_frame << BPER_MB_NORMBITS) / cpi->common.MBs;
i = cpi->active_best_quality;
do {
bits_per_mb_at_this_q = (int)vp9_bits_per_mb(cpi->common.frame_type, i,
correction_factor);
if (bits_per_mb_at_this_q <= target_bits_per_mb) {
if ((target_bits_per_mb - bits_per_mb_at_this_q) <= last_error)
q = i;
else
q = i - 1;
break;
} else {
last_error = bits_per_mb_at_this_q - target_bits_per_mb;
}
} while (++i <= cpi->active_worst_quality);
return q;
}
static int estimate_keyframe_frequency(VP9_COMP *cpi) {
int i;
// Average key frame frequency
int av_key_frame_frequency = 0;
/* First key frame at start of sequence is a special case. We have no
* frequency data.
*/
if (cpi->key_frame_count == 1) {
/* Assume a default of 1 kf every 2 seconds, or the max kf interval,
* whichever is smaller.
*/
int key_freq = cpi->oxcf.key_freq > 0 ? cpi->oxcf.key_freq : 1;
av_key_frame_frequency = (int)cpi->output_framerate * 2;
if (cpi->oxcf.auto_key && av_key_frame_frequency > key_freq)
av_key_frame_frequency = cpi->oxcf.key_freq;
cpi->prior_key_frame_distance[KEY_FRAME_CONTEXT - 1]
= av_key_frame_frequency;
} else {
unsigned int total_weight = 0;
int last_kf_interval =
(cpi->frames_since_key > 0) ? cpi->frames_since_key : 1;
/* reset keyframe context and calculate weighted average of last
* KEY_FRAME_CONTEXT keyframes
*/
for (i = 0; i < KEY_FRAME_CONTEXT; i++) {
if (i < KEY_FRAME_CONTEXT - 1)
cpi->prior_key_frame_distance[i]
= cpi->prior_key_frame_distance[i + 1];
else
cpi->prior_key_frame_distance[i] = last_kf_interval;
av_key_frame_frequency += prior_key_frame_weight[i]
* cpi->prior_key_frame_distance[i];
total_weight += prior_key_frame_weight[i];
}
av_key_frame_frequency /= total_weight;
}
return av_key_frame_frequency;
}
void vp9_adjust_key_frame_context(VP9_COMP *cpi) {
// Clear down mmx registers to allow floating point in what follows
vp9_clear_system_state();
cpi->frames_since_key = 0;
cpi->key_frame_count++;
}
void vp9_compute_frame_size_bounds(VP9_COMP *cpi, int *frame_under_shoot_limit,
int *frame_over_shoot_limit) {
// Set-up bounds on acceptable frame size:
if (cpi->oxcf.fixed_q >= 0) {
// Fixed Q scenario: frame size never outranges target (there is no target!)
*frame_under_shoot_limit = 0;
*frame_over_shoot_limit = INT_MAX;
} else {
if (cpi->common.frame_type == KEY_FRAME) {
*frame_over_shoot_limit = cpi->this_frame_target * 9 / 8;
*frame_under_shoot_limit = cpi->this_frame_target * 7 / 8;
} else {
if (cpi->refresh_alt_ref_frame || cpi->refresh_golden_frame) {
*frame_over_shoot_limit = cpi->this_frame_target * 9 / 8;
*frame_under_shoot_limit = cpi->this_frame_target * 7 / 8;
} else {
// Stron overshoot limit for constrained quality
if (cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY) {
*frame_over_shoot_limit = cpi->this_frame_target * 11 / 8;
*frame_under_shoot_limit = cpi->this_frame_target * 2 / 8;
} else {
*frame_over_shoot_limit = cpi->this_frame_target * 11 / 8;
*frame_under_shoot_limit = cpi->this_frame_target * 5 / 8;
}
}
}
// For very small rate targets where the fractional adjustment
// (eg * 7/8) may be tiny make sure there is at least a minimum
// range.
*frame_over_shoot_limit += 200;
*frame_under_shoot_limit -= 200;
if (*frame_under_shoot_limit < 0)
*frame_under_shoot_limit = 0;
}
}
// return of 0 means drop frame
int vp9_pick_frame_size(VP9_COMP *cpi) {
VP9_COMMON *cm = &cpi->common;
if (cm->frame_type == KEY_FRAME)
calc_iframe_target_size(cpi);
else
calc_pframe_target_size(cpi);
return 1;
}