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fast auto-determined filtering strength

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kLevelsFromDelta[sharpness][delta] is an inverse look-up table
that tells the minimum filtering strength needed to trigger the
filtering of a step with amplitude 'delta'. We use this table
in various situations:

a) when computing the initial (/global) filtering
strength for each segment. We look at the quantization
step and deduce the proper filtering strength needed
to result this quantization noise (talking the -f option
into account).

b) during intra16 calculation, when a block ends up
very empty (only DC coeffs are non-zero, all ACs have
vanished). We'll rely on the in-loop filtering to
restore the smoothness (if the source was gradient-like
smooth. That's why we look at the distortion too before
triggering the filtering).

Step b) goes _in addition_ to a), potentially raising
the filtering strength if blockiness is likely.

Change-Id: Icaeca93ef21da195b079e6587a44d9edfc8e9efa
This commit is contained in:
skal 2013-10-29 20:13:29 +01:00
parent 43148b6cd2
commit f8bfd5cd1e
4 changed files with 122 additions and 26 deletions
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2
src/enc/config.c
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@ -33,7 +33,7 @@ int WebPConfigInitInternal(WebPConfig* config,
config->target_PSNR = 0.;
config->method = 4;
config->sns_strength = 50;
config->filter_strength = 60; // rather high filtering, helps w/ gradients.
config->filter_strength = 60; // mid-filtering
config->filter_sharpness = 0;
config->filter_type = 1; // default: strong (so U/V is filtered too)
config->partitions = 0;

74
src/enc/filter.c
View File

@ -11,12 +11,58 @@
//
// Author: somnath@google.com (Somnath Banerjee)
#include <assert.h>
#include "./vp8enci.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
// this table gives, for a given sharpness, the filtering strength to be
// used (at least) in order to filter a given edge step delta.
#define MAX_DELTA_SIZE 64
static const uint8_t kLevelsFromDelta[8][MAX_DELTA_SIZE] = {
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 },
{ 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 17, 18,
20, 21, 23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42,
44, 45, 47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 19,
20, 22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43,
44, 46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 18, 19,
21, 22, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 42, 43,
45, 46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 63, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 14, 15, 17, 18, 20,
21, 23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42, 44,
45, 47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 4, 5, 7, 8, 9, 11, 12, 13, 15, 16, 17, 19, 20,
22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43, 44,
46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 63, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 4, 5, 7, 8, 9, 11, 12, 13, 15, 16, 18, 19, 21,
22, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 42, 43, 45,
46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 63, 63, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
{ 0, 1, 2, 4, 5, 7, 8, 9, 11, 12, 14, 15, 17, 18, 20, 21,
23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42, 44, 45,
47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63, 63, 63,
63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 }
};
int VP8FilterStrengthFromDelta(int sharpness, int delta) {
const int pos = (delta < MAX_DELTA_SIZE) ? delta : MAX_DELTA_SIZE - 1;
assert(sharpness >= 0 && sharpness <= 7);
return kLevelsFromDelta[sharpness][pos];
}
// -----------------------------------------------------------------------------
// NOTE: clip1, tables and InitTables are repeated entries of dsp.c
static uint8_t abs0[255 + 255 + 1]; // abs(i)
static uint8_t abs1[255 + 255 + 1]; // abs(i)>>1
@ -353,12 +399,13 @@ void VP8InitFilter(VP8EncIterator* const it) {
void VP8StoreFilterStats(VP8EncIterator* const it) {
int d;
VP8Encoder* const enc = it->enc_;
const int s = it->mb_->segment_;
const int level0 = it->enc_->dqm_[s].fstrength_; // TODO: ref_lf_delta[]
const int level0 = enc->dqm_[s].fstrength_; // TODO: ref_lf_delta[]
// explore +/-quant range of values around level0
const int delta_min = -it->enc_->dqm_[s].quant_;
const int delta_max = it->enc_->dqm_[s].quant_;
const int delta_min = -enc->dqm_[s].quant_;
const int delta_max = enc->dqm_[s].quant_;
const int step_size = (delta_max - delta_min >= 4) ? 4 : 1;
if (it->lf_stats_ == NULL) return;
@ -385,9 +432,9 @@ void VP8StoreFilterStats(VP8EncIterator* const it) {
}
void VP8AdjustFilterStrength(VP8EncIterator* const it) {
VP8Encoder* const enc = it->enc_;
if (it->lf_stats_ != NULL) {
int s;
VP8Encoder* const enc = it->enc_;
for (s = 0; s < NUM_MB_SEGMENTS; s++) {
int i, best_level = 0;
// Improvement over filter level 0 should be at least 1e-5 (relatively)
@ -401,8 +448,27 @@ void VP8AdjustFilterStrength(VP8EncIterator* const it) {
}
enc->dqm_[s].fstrength_ = best_level;
}
} else if (enc->config_->filter_strength > 0) {
int max_level = 0;
int s;
for (s = 0; s < NUM_MB_SEGMENTS; s++) {
VP8SegmentInfo* const dqm = &enc->dqm_[s];
// this '>> 3' accounts for some inverse WHT scaling
const int delta = (dqm->max_edge_ * dqm->y2_.q_[1]) >> 3;
const int level =
VP8FilterStrengthFromDelta(enc->filter_hdr_.sharpness_, delta);
if (level > dqm->fstrength_) {
dqm->fstrength_ = level;
}
if (max_level < dqm->fstrength_) {
max_level = dqm->fstrength_;
}
}
enc->filter_hdr_.level_ = max_level;
}
}
// -----------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"

50
src/enc/quant.c
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@ -13,6 +13,7 @@
#include <assert.h>
#include <math.h>
#include <stdlib.h> // for abs()
#include "./vp8enci.h"
#include "./cost.h"
@ -182,8 +183,6 @@ static void SetupMatrices(VP8Encoder* enc) {
q16 = ExpandMatrix(&m->y2_, 1);
quv = ExpandMatrix(&m->uv_, 2);
// TODO: Switch to kLambda*[] tables?
{
m->lambda_i4_ = (3 * q4 * q4) >> 7;
m->lambda_i16_ = (3 * q16 * q16);
m->lambda_uv_ = (3 * quv * quv) >> 6;
@ -192,7 +191,9 @@ static void SetupMatrices(VP8Encoder* enc) {
m->lambda_trellis_i16_ = (q16 * q16) >> 2;
m->lambda_trellis_uv_ = (quv *quv) << 1;
m->tlambda_ = (tlambda_scale * q4) >> 5;
}
m->min_disto_ = 10 * m->y1_.q_[0]; // quantization-aware min disto
m->max_edge_ = 0;
}
}
@ -201,16 +202,21 @@ static void SetupMatrices(VP8Encoder* enc) {
// Very small filter-strength values have close to no visual effect. So we can
// save a little decoding-CPU by turning filtering off for these.
#define FSTRENGTH_CUTOFF 3
#define FSTRENGTH_CUTOFF 2
static void SetupFilterStrength(VP8Encoder* const enc) {
int i;
const int level0 = enc->config_->filter_strength;
// level0 is in [0..500]. Using '-f 50' as filter_strength is mid-filtering.
const int level0 = 5 * enc->config_->filter_strength;
for (i = 0; i < NUM_MB_SEGMENTS; ++i) {
// Segments with lower quantizer will be less filtered. TODO: tune (wrt SNS)
const int level = level0 * 256 * enc->dqm_[i].quant_ / 128;
const int f = level / (256 + enc->dqm_[i].beta_);
enc->dqm_[i].fstrength_ = (f < FSTRENGTH_CUTOFF) ? 0 : (f > 63) ? 63 : f;
VP8SegmentInfo* const m = &enc->dqm_[i];
// We focus on the quantization of AC coeffs.
const int qstep = kAcTable[clip(m->quant_, 0, 127)] >> 2;
const int base_strength =
VP8FilterStrengthFromDelta(enc->filter_hdr_.sharpness_, qstep);
// Segments with lower complexity ('beta') will be less filtered.
const int f = base_strength * level0 / (256 + m->beta_);
m->fstrength_ = (f < FSTRENGTH_CUTOFF) ? 0 : (f > 63) ? 63 : f;
}
// We record the initial strength (mainly for the case of 1-segment only).
enc->filter_hdr_.level_ = enc->dqm_[0].fstrength_;
@ -649,10 +655,10 @@ static int ReconstructIntra16(VP8EncIterator* const it,
VP8ModeScore* const rd,
uint8_t* const yuv_out,
int mode) {
const VP8Encoder* const enc = it->enc_;
VP8Encoder* const enc = it->enc_;
const uint8_t* const ref = it->yuv_p_ + VP8I16ModeOffsets[mode];
const uint8_t* const src = it->yuv_in_ + Y_OFF;
const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_];
VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_];
int nz = 0;
int n;
int16_t tmp[16][16], dc_tmp[16];
@ -758,6 +764,17 @@ static int ReconstructUV(VP8EncIterator* const it, VP8ModeScore* const rd,
// RD-opt decision. Reconstruct each modes, evalue distortion and bit-cost.
// Pick the mode is lower RD-cost = Rate + lamba * Distortion.
static void StoreMaxDelta(VP8SegmentInfo* const dqm, const int16_t DCs[16]) {
// We look at the first three AC coefficients to determine what is the average
// delta between each sub-4x4 block.
const int v0 = abs(DCs[1]);
const int v1 = abs(DCs[4]);
const int v2 = abs(DCs[5]);
int max_v = (v0 > v1) ? v1 : v0;
max_v = (v2 > max_v) ? v2 : max_v;
if (max_v > dqm->max_edge_) dqm->max_edge_ = max_v;
}
static void SwapPtr(uint8_t** a, uint8_t** b) {
uint8_t* const tmp = *a;
*a = *b;
@ -769,8 +786,8 @@ static void SwapOut(VP8EncIterator* const it) {
}
static void PickBestIntra16(VP8EncIterator* const it, VP8ModeScore* const rd) {
const VP8Encoder* const enc = it->enc_;
const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_];
VP8Encoder* const enc = it->enc_;
VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_];
const int lambda = dqm->lambda_i16_;
const int tlambda = dqm->tlambda_;
const uint8_t* const src = it->yuv_in_ + Y_OFF;
@ -805,6 +822,13 @@ static void PickBestIntra16(VP8EncIterator* const it, VP8ModeScore* const rd) {
}
SetRDScore(dqm->lambda_mode_, rd); // finalize score for mode decision.
VP8SetIntra16Mode(it, rd->mode_i16);
// we have a blocky macroblock (only DCs are non-zero) with fairly high
// distortion, record max delta so we can later adjust the minimal filtering
// strength needed to smooth these blocks out.
if ((rd->nz & 0xffff) == 0 && rd->D > dqm->min_disto_) {
StoreMaxDelta(dqm, rd->y_dc_levels);
}
}
//------------------------------------------------------------------------------

6
src/enc/vp8enci.h
View File

@ -248,6 +248,8 @@ typedef struct {
int beta_; // filter-susceptibility, range [0,255].
int quant_; // final segment quantizer.
int fstrength_; // final in-loop filtering strength
int max_edge_; // max edge delta (for filtering strength)
int min_disto_; // minimum distortion required to trigger filtering record
// reactivities
int lambda_i16_, lambda_i4_, lambda_uv_;
int lambda_mode_, lambda_trellis_, tlambda_;
@ -555,6 +557,10 @@ void VP8InitFilter(VP8EncIterator* const it);
void VP8StoreFilterStats(VP8EncIterator* const it);
void VP8AdjustFilterStrength(VP8EncIterator* const it);
// returns the approximate filtering strength needed to smooth a edge
// step of 'delta', given a sharpness parameter 'sharpness'.
int VP8FilterStrengthFromDelta(int sharpness, int delta);
//------------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)