1// Copyright 2011 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// Selecting filter level
11//
12// Author: somnath@google.com (Somnath Banerjee)
13
14#include <assert.h>
15#include "./vp8enci.h"
16#include "../dsp/dsp.h"
17
18// This table gives, for a given sharpness, the filtering strength to be
19// used (at least) in order to filter a given edge step delta.
20// This is constructed by brute force inspection: for all delta, we iterate
21// over all possible filtering strength / thresh until needs_filter() returns
22// true.
23#define MAX_DELTA_SIZE 64
24static const uint8_t kLevelsFromDelta[8][MAX_DELTA_SIZE] = {
25  { 0,   1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15,
26    16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
27    32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
28    48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 },
29  { 0,  1,  2,  3,  5,  6,  7,  8,  9, 11, 12, 13, 14, 15, 17, 18,
30    20, 21, 23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42,
31    44, 45, 47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63,
32    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
33  {  0,  1,  2,  3,  5,  6,  7,  8,  9, 11, 12, 13, 14, 16, 17, 19,
34    20, 22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43,
35    44, 46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 63, 63, 63,
36    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
37  {  0,  1,  2,  3,  5,  6,  7,  8,  9, 11, 12, 13, 15, 16, 18, 19,
38    21, 22, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 42, 43,
39    45, 46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 63, 63, 63, 63,
40    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
41  {  0,  1,  2,  3,  5,  6,  7,  8,  9, 11, 12, 14, 15, 17, 18, 20,
42    21, 23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42, 44,
43    45, 47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63, 63,
44    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
45  {  0,  1,  2,  4,  5,  7,  8,  9, 11, 12, 13, 15, 16, 17, 19, 20,
46    22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43, 44,
47    46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 63, 63, 63, 63,
48    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
49  {  0,  1,  2,  4,  5,  7,  8,  9, 11, 12, 13, 15, 16, 18, 19, 21,
50    22, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 42, 43, 45,
51    46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 63, 63, 63, 63, 63,
52    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 },
53  {  0,  1,  2,  4,  5,  7,  8,  9, 11, 12, 14, 15, 17, 18, 20, 21,
54    23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 38, 39, 41, 42, 44, 45,
55    47, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 63, 63, 63, 63,
56    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63 }
57};
58
59int VP8FilterStrengthFromDelta(int sharpness, int delta) {
60  const int pos = (delta < MAX_DELTA_SIZE) ? delta : MAX_DELTA_SIZE - 1;
61  assert(sharpness >= 0 && sharpness <= 7);
62  return kLevelsFromDelta[sharpness][pos];
63}
64
65//------------------------------------------------------------------------------
66// Paragraph 15.4: compute the inner-edge filtering strength
67
68static int GetILevel(int sharpness, int level) {
69  if (sharpness > 0) {
70    if (sharpness > 4) {
71      level >>= 2;
72    } else {
73      level >>= 1;
74    }
75    if (level > 9 - sharpness) {
76      level = 9 - sharpness;
77    }
78  }
79  if (level < 1) level = 1;
80  return level;
81}
82
83static void DoFilter(const VP8EncIterator* const it, int level) {
84  const VP8Encoder* const enc = it->enc_;
85  const int ilevel = GetILevel(enc->config_->filter_sharpness, level);
86  const int limit = 2 * level + ilevel;
87
88  uint8_t* const y_dst = it->yuv_out2_ + Y_OFF;
89  uint8_t* const u_dst = it->yuv_out2_ + U_OFF;
90  uint8_t* const v_dst = it->yuv_out2_ + V_OFF;
91
92  // copy current block to yuv_out2_
93  memcpy(y_dst, it->yuv_out_, YUV_SIZE * sizeof(uint8_t));
94
95  if (enc->filter_hdr_.simple_ == 1) {   // simple
96    VP8SimpleHFilter16i(y_dst, BPS, limit);
97    VP8SimpleVFilter16i(y_dst, BPS, limit);
98  } else {    // complex
99    const int hev_thresh = (level >= 40) ? 2 : (level >= 15) ? 1 : 0;
100    VP8HFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
101    VP8HFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
102    VP8VFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
103    VP8VFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
104  }
105}
106
107//------------------------------------------------------------------------------
108// SSIM metric
109
110enum { KERNEL = 3 };
111static const double kMinValue = 1.e-10;  // minimal threshold
112
113void VP8SSIMAddStats(const DistoStats* const src, DistoStats* const dst) {
114  dst->w   += src->w;
115  dst->xm  += src->xm;
116  dst->ym  += src->ym;
117  dst->xxm += src->xxm;
118  dst->xym += src->xym;
119  dst->yym += src->yym;
120}
121
122static void VP8SSIMAccumulate(const uint8_t* src1, int stride1,
123                              const uint8_t* src2, int stride2,
124                              int xo, int yo, int W, int H,
125                              DistoStats* const stats) {
126  const int ymin = (yo - KERNEL < 0) ? 0 : yo - KERNEL;
127  const int ymax = (yo + KERNEL > H - 1) ? H - 1 : yo + KERNEL;
128  const int xmin = (xo - KERNEL < 0) ? 0 : xo - KERNEL;
129  const int xmax = (xo + KERNEL > W - 1) ? W - 1 : xo + KERNEL;
130  int x, y;
131  src1 += ymin * stride1;
132  src2 += ymin * stride2;
133  for (y = ymin; y <= ymax; ++y, src1 += stride1, src2 += stride2) {
134    for (x = xmin; x <= xmax; ++x) {
135      const int s1 = src1[x];
136      const int s2 = src2[x];
137      stats->w   += 1;
138      stats->xm  += s1;
139      stats->ym  += s2;
140      stats->xxm += s1 * s1;
141      stats->xym += s1 * s2;
142      stats->yym += s2 * s2;
143    }
144  }
145}
146
147double VP8SSIMGet(const DistoStats* const stats) {
148  const double xmxm = stats->xm * stats->xm;
149  const double ymym = stats->ym * stats->ym;
150  const double xmym = stats->xm * stats->ym;
151  const double w2 = stats->w * stats->w;
152  double sxx = stats->xxm * stats->w - xmxm;
153  double syy = stats->yym * stats->w - ymym;
154  double sxy = stats->xym * stats->w - xmym;
155  double C1, C2;
156  double fnum;
157  double fden;
158  // small errors are possible, due to rounding. Clamp to zero.
159  if (sxx < 0.) sxx = 0.;
160  if (syy < 0.) syy = 0.;
161  C1 = 6.5025 * w2;
162  C2 = 58.5225 * w2;
163  fnum = (2 * xmym + C1) * (2 * sxy + C2);
164  fden = (xmxm + ymym + C1) * (sxx + syy + C2);
165  return (fden != 0.) ? fnum / fden : kMinValue;
166}
167
168double VP8SSIMGetSquaredError(const DistoStats* const s) {
169  if (s->w > 0.) {
170    const double iw2 = 1. / (s->w * s->w);
171    const double sxx = s->xxm * s->w - s->xm * s->xm;
172    const double syy = s->yym * s->w - s->ym * s->ym;
173    const double sxy = s->xym * s->w - s->xm * s->ym;
174    const double SSE = iw2 * (sxx + syy - 2. * sxy);
175    if (SSE > kMinValue) return SSE;
176  }
177  return kMinValue;
178}
179
180void VP8SSIMAccumulatePlane(const uint8_t* src1, int stride1,
181                            const uint8_t* src2, int stride2,
182                            int W, int H, DistoStats* const stats) {
183  int x, y;
184  for (y = 0; y < H; ++y) {
185    for (x = 0; x < W; ++x) {
186      VP8SSIMAccumulate(src1, stride1, src2, stride2, x, y, W, H, stats);
187    }
188  }
189}
190
191static double GetMBSSIM(const uint8_t* yuv1, const uint8_t* yuv2) {
192  int x, y;
193  DistoStats s = { .0, .0, .0, .0, .0, .0 };
194
195  // compute SSIM in a 10 x 10 window
196  for (x = 3; x < 13; x++) {
197    for (y = 3; y < 13; y++) {
198      VP8SSIMAccumulate(yuv1 + Y_OFF, BPS, yuv2 + Y_OFF, BPS, x, y, 16, 16, &s);
199    }
200  }
201  for (x = 1; x < 7; x++) {
202    for (y = 1; y < 7; y++) {
203      VP8SSIMAccumulate(yuv1 + U_OFF, BPS, yuv2 + U_OFF, BPS, x, y, 8, 8, &s);
204      VP8SSIMAccumulate(yuv1 + V_OFF, BPS, yuv2 + V_OFF, BPS, x, y, 8, 8, &s);
205    }
206  }
207  return VP8SSIMGet(&s);
208}
209
210//------------------------------------------------------------------------------
211// Exposed APIs: Encoder should call the following 3 functions to adjust
212// loop filter strength
213
214void VP8InitFilter(VP8EncIterator* const it) {
215  if (it->lf_stats_ != NULL) {
216    int s, i;
217    for (s = 0; s < NUM_MB_SEGMENTS; s++) {
218      for (i = 0; i < MAX_LF_LEVELS; i++) {
219        (*it->lf_stats_)[s][i] = 0;
220      }
221    }
222  }
223}
224
225void VP8StoreFilterStats(VP8EncIterator* const it) {
226  int d;
227  VP8Encoder* const enc = it->enc_;
228  const int s = it->mb_->segment_;
229  const int level0 = enc->dqm_[s].fstrength_;  // TODO: ref_lf_delta[]
230
231  // explore +/-quant range of values around level0
232  const int delta_min = -enc->dqm_[s].quant_;
233  const int delta_max = enc->dqm_[s].quant_;
234  const int step_size = (delta_max - delta_min >= 4) ? 4 : 1;
235
236  if (it->lf_stats_ == NULL) return;
237
238  // NOTE: Currently we are applying filter only across the sublock edges
239  // There are two reasons for that.
240  // 1. Applying filter on macro block edges will change the pixels in
241  // the left and top macro blocks. That will be hard to restore
242  // 2. Macro Blocks on the bottom and right are not yet compressed. So we
243  // cannot apply filter on the right and bottom macro block edges.
244  if (it->mb_->type_ == 1 && it->mb_->skip_) return;
245
246  // Always try filter level  zero
247  (*it->lf_stats_)[s][0] += GetMBSSIM(it->yuv_in_, it->yuv_out_);
248
249  for (d = delta_min; d <= delta_max; d += step_size) {
250    const int level = level0 + d;
251    if (level <= 0 || level >= MAX_LF_LEVELS) {
252      continue;
253    }
254    DoFilter(it, level);
255    (*it->lf_stats_)[s][level] += GetMBSSIM(it->yuv_in_, it->yuv_out2_);
256  }
257}
258
259void VP8AdjustFilterStrength(VP8EncIterator* const it) {
260  VP8Encoder* const enc = it->enc_;
261  if (it->lf_stats_ != NULL) {
262    int s;
263    for (s = 0; s < NUM_MB_SEGMENTS; s++) {
264      int i, best_level = 0;
265      // Improvement over filter level 0 should be at least 1e-5 (relatively)
266      double best_v = 1.00001 * (*it->lf_stats_)[s][0];
267      for (i = 1; i < MAX_LF_LEVELS; i++) {
268        const double v = (*it->lf_stats_)[s][i];
269        if (v > best_v) {
270          best_v = v;
271          best_level = i;
272        }
273      }
274      enc->dqm_[s].fstrength_ = best_level;
275    }
276  } else if (enc->config_->filter_strength > 0) {
277    int max_level = 0;
278    int s;
279    for (s = 0; s < NUM_MB_SEGMENTS; s++) {
280      VP8SegmentInfo* const dqm = &enc->dqm_[s];
281      // this '>> 3' accounts for some inverse WHT scaling
282      const int delta = (dqm->max_edge_ * dqm->y2_.q_[1]) >> 3;
283      const int level =
284          VP8FilterStrengthFromDelta(enc->filter_hdr_.sharpness_, delta);
285      if (level > dqm->fstrength_) {
286        dqm->fstrength_ = level;
287      }
288      if (max_level < dqm->fstrength_) {
289        max_level = dqm->fstrength_;
290      }
291    }
292    enc->filter_hdr_.level_ = max_level;
293  }
294}
295
296// -----------------------------------------------------------------------------
297