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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 "src/enc/vp8i_enc.h"
16 #include "src/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
24 static 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 
VP8FilterStrengthFromDelta(int sharpness,int delta)59 int 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 
68 #if !defined(WEBP_REDUCE_SIZE)
69 
GetILevel(int sharpness,int level)70 static int GetILevel(int sharpness, int level) {
71   if (sharpness > 0) {
72     if (sharpness > 4) {
73       level >>= 2;
74     } else {
75       level >>= 1;
76     }
77     if (level > 9 - sharpness) {
78       level = 9 - sharpness;
79     }
80   }
81   if (level < 1) level = 1;
82   return level;
83 }
84 
DoFilter(const VP8EncIterator * const it,int level)85 static void DoFilter(const VP8EncIterator* const it, int level) {
86   const VP8Encoder* const enc = it->enc_;
87   const int ilevel = GetILevel(enc->config_->filter_sharpness, level);
88   const int limit = 2 * level + ilevel;
89 
90   uint8_t* const y_dst = it->yuv_out2_ + Y_OFF_ENC;
91   uint8_t* const u_dst = it->yuv_out2_ + U_OFF_ENC;
92   uint8_t* const v_dst = it->yuv_out2_ + V_OFF_ENC;
93 
94   // copy current block to yuv_out2_
95   memcpy(y_dst, it->yuv_out_, YUV_SIZE_ENC * sizeof(uint8_t));
96 
97   if (enc->filter_hdr_.simple_ == 1) {   // simple
98     VP8SimpleHFilter16i(y_dst, BPS, limit);
99     VP8SimpleVFilter16i(y_dst, BPS, limit);
100   } else {    // complex
101     const int hev_thresh = (level >= 40) ? 2 : (level >= 15) ? 1 : 0;
102     VP8HFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
103     VP8HFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
104     VP8VFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
105     VP8VFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
106   }
107 }
108 
109 //------------------------------------------------------------------------------
110 // SSIM metric for one macroblock
111 
GetMBSSIM(const uint8_t * yuv1,const uint8_t * yuv2)112 static double GetMBSSIM(const uint8_t* yuv1, const uint8_t* yuv2) {
113   int x, y;
114   double sum = 0.;
115 
116   // compute SSIM in a 10 x 10 window
117   for (y = VP8_SSIM_KERNEL; y < 16 - VP8_SSIM_KERNEL; y++) {
118     for (x = VP8_SSIM_KERNEL; x < 16 - VP8_SSIM_KERNEL; x++) {
119       sum += VP8SSIMGetClipped(yuv1 + Y_OFF_ENC, BPS, yuv2 + Y_OFF_ENC, BPS,
120                                x, y, 16, 16);
121     }
122   }
123   for (x = 1; x < 7; x++) {
124     for (y = 1; y < 7; y++) {
125       sum += VP8SSIMGetClipped(yuv1 + U_OFF_ENC, BPS, yuv2 + U_OFF_ENC, BPS,
126                                x, y, 8, 8);
127       sum += VP8SSIMGetClipped(yuv1 + V_OFF_ENC, BPS, yuv2 + V_OFF_ENC, BPS,
128                                x, y, 8, 8);
129     }
130   }
131   return sum;
132 }
133 
134 #endif  // !defined(WEBP_REDUCE_SIZE)
135 
136 //------------------------------------------------------------------------------
137 // Exposed APIs: Encoder should call the following 3 functions to adjust
138 // loop filter strength
139 
VP8InitFilter(VP8EncIterator * const it)140 void VP8InitFilter(VP8EncIterator* const it) {
141 #if !defined(WEBP_REDUCE_SIZE)
142   if (it->lf_stats_ != NULL) {
143     int s, i;
144     for (s = 0; s < NUM_MB_SEGMENTS; s++) {
145       for (i = 0; i < MAX_LF_LEVELS; i++) {
146         (*it->lf_stats_)[s][i] = 0;
147       }
148     }
149     VP8SSIMDspInit();
150   }
151 #else
152   (void)it;
153 #endif
154 }
155 
VP8StoreFilterStats(VP8EncIterator * const it)156 void VP8StoreFilterStats(VP8EncIterator* const it) {
157 #if !defined(WEBP_REDUCE_SIZE)
158   int d;
159   VP8Encoder* const enc = it->enc_;
160   const int s = it->mb_->segment_;
161   const int level0 = enc->dqm_[s].fstrength_;
162 
163   // explore +/-quant range of values around level0
164   const int delta_min = -enc->dqm_[s].quant_;
165   const int delta_max = enc->dqm_[s].quant_;
166   const int step_size = (delta_max - delta_min >= 4) ? 4 : 1;
167 
168   if (it->lf_stats_ == NULL) return;
169 
170   // NOTE: Currently we are applying filter only across the sublock edges
171   // There are two reasons for that.
172   // 1. Applying filter on macro block edges will change the pixels in
173   // the left and top macro blocks. That will be hard to restore
174   // 2. Macro Blocks on the bottom and right are not yet compressed. So we
175   // cannot apply filter on the right and bottom macro block edges.
176   if (it->mb_->type_ == 1 && it->mb_->skip_) return;
177 
178   // Always try filter level  zero
179   (*it->lf_stats_)[s][0] += GetMBSSIM(it->yuv_in_, it->yuv_out_);
180 
181   for (d = delta_min; d <= delta_max; d += step_size) {
182     const int level = level0 + d;
183     if (level <= 0 || level >= MAX_LF_LEVELS) {
184       continue;
185     }
186     DoFilter(it, level);
187     (*it->lf_stats_)[s][level] += GetMBSSIM(it->yuv_in_, it->yuv_out2_);
188   }
189 #else  // defined(WEBP_REDUCE_SIZE)
190   (void)it;
191 #endif  // !defined(WEBP_REDUCE_SIZE)
192 }
193 
VP8AdjustFilterStrength(VP8EncIterator * const it)194 void VP8AdjustFilterStrength(VP8EncIterator* const it) {
195   VP8Encoder* const enc = it->enc_;
196 #if !defined(WEBP_REDUCE_SIZE)
197   if (it->lf_stats_ != NULL) {
198     int s;
199     for (s = 0; s < NUM_MB_SEGMENTS; s++) {
200       int i, best_level = 0;
201       // Improvement over filter level 0 should be at least 1e-5 (relatively)
202       double best_v = 1.00001 * (*it->lf_stats_)[s][0];
203       for (i = 1; i < MAX_LF_LEVELS; i++) {
204         const double v = (*it->lf_stats_)[s][i];
205         if (v > best_v) {
206           best_v = v;
207           best_level = i;
208         }
209       }
210       enc->dqm_[s].fstrength_ = best_level;
211     }
212     return;
213   }
214 #endif  // !defined(WEBP_REDUCE_SIZE)
215   if (enc->config_->filter_strength > 0) {
216     int max_level = 0;
217     int s;
218     for (s = 0; s < NUM_MB_SEGMENTS; s++) {
219       VP8SegmentInfo* const dqm = &enc->dqm_[s];
220       // this '>> 3' accounts for some inverse WHT scaling
221       const int delta = (dqm->max_edge_ * dqm->y2_.q_[1]) >> 3;
222       const int level =
223           VP8FilterStrengthFromDelta(enc->filter_hdr_.sharpness_, delta);
224       if (level > dqm->fstrength_) {
225         dqm->fstrength_ = level;
226       }
227       if (max_level < dqm->fstrength_) {
228         max_level = dqm->fstrength_;
229       }
230     }
231     enc->filter_hdr_.level_ = max_level;
232   }
233 }
234 
235 // -----------------------------------------------------------------------------
236