1/*
2 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11#include <assert.h>
12#include <limits.h>
13
14#include "./vpx_scale_rtcd.h"
15
16#include "vpx_mem/vpx_mem.h"
17
18#include "vp9/common/vp9_loopfilter.h"
19#include "vp9/common/vp9_onyxc_int.h"
20#include "vp9/common/vp9_quant_common.h"
21
22#include "vp9/encoder/vp9_encoder.h"
23#include "vp9/encoder/vp9_picklpf.h"
24#include "vp9/encoder/vp9_quantize.h"
25
26static int get_max_filter_level(const VP9_COMP *cpi) {
27  if (cpi->oxcf.pass == 2) {
28    return cpi->twopass.section_intra_rating > 8 ? MAX_LOOP_FILTER * 3 / 4
29                                                 : MAX_LOOP_FILTER;
30  } else {
31    return MAX_LOOP_FILTER;
32  }
33}
34
35
36static int try_filter_frame(const YV12_BUFFER_CONFIG *sd, VP9_COMP *const cpi,
37                            int filt_level, int partial_frame) {
38  VP9_COMMON *const cm = &cpi->common;
39  int filt_err;
40
41  vp9_loop_filter_frame(cm->frame_to_show, cm, &cpi->mb.e_mbd, filt_level, 1,
42                        partial_frame);
43  filt_err = vp9_get_y_sse(sd, cm->frame_to_show);
44
45  // Re-instate the unfiltered frame
46  vpx_yv12_copy_y(&cpi->last_frame_uf, cm->frame_to_show);
47
48  return filt_err;
49}
50
51static int search_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
52                               int partial_frame) {
53  const VP9_COMMON *const cm = &cpi->common;
54  const struct loopfilter *const lf = &cm->lf;
55  const int min_filter_level = 0;
56  const int max_filter_level = get_max_filter_level(cpi);
57  int filt_direction = 0;
58  int best_err, filt_best;
59
60  // Start the search at the previous frame filter level unless it is now out of
61  // range.
62  int filt_mid = clamp(lf->filter_level, min_filter_level, max_filter_level);
63  int filter_step = filt_mid < 16 ? 4 : filt_mid / 4;
64  // Sum squared error at each filter level
65  int ss_err[MAX_LOOP_FILTER + 1];
66
67  // Set each entry to -1
68  vpx_memset(ss_err, 0xFF, sizeof(ss_err));
69
70  //  Make a copy of the unfiltered / processed recon buffer
71  vpx_yv12_copy_y(cm->frame_to_show, &cpi->last_frame_uf);
72
73  best_err = try_filter_frame(sd, cpi, filt_mid, partial_frame);
74  filt_best = filt_mid;
75  ss_err[filt_mid] = best_err;
76
77  while (filter_step > 0) {
78    const int filt_high = MIN(filt_mid + filter_step, max_filter_level);
79    const int filt_low = MAX(filt_mid - filter_step, min_filter_level);
80
81    // Bias against raising loop filter in favor of lowering it.
82    int bias = (best_err >> (15 - (filt_mid / 8))) * filter_step;
83
84    if ((cpi->oxcf.pass == 2) && (cpi->twopass.section_intra_rating < 20))
85      bias = (bias * cpi->twopass.section_intra_rating) / 20;
86
87    // yx, bias less for large block size
88    if (cm->tx_mode != ONLY_4X4)
89      bias >>= 1;
90
91    if (filt_direction <= 0 && filt_low != filt_mid) {
92      // Get Low filter error score
93      if (ss_err[filt_low] < 0) {
94        ss_err[filt_low] = try_filter_frame(sd, cpi, filt_low, partial_frame);
95      }
96      // If value is close to the best so far then bias towards a lower loop
97      // filter value.
98      if ((ss_err[filt_low] - bias) < best_err) {
99        // Was it actually better than the previous best?
100        if (ss_err[filt_low] < best_err)
101          best_err = ss_err[filt_low];
102
103        filt_best = filt_low;
104      }
105    }
106
107    // Now look at filt_high
108    if (filt_direction >= 0 && filt_high != filt_mid) {
109      if (ss_err[filt_high] < 0) {
110        ss_err[filt_high] = try_filter_frame(sd, cpi, filt_high, partial_frame);
111      }
112      // Was it better than the previous best?
113      if (ss_err[filt_high] < (best_err - bias)) {
114        best_err = ss_err[filt_high];
115        filt_best = filt_high;
116      }
117    }
118
119    // Half the step distance if the best filter value was the same as last time
120    if (filt_best == filt_mid) {
121      filter_step /= 2;
122      filt_direction = 0;
123    } else {
124      filt_direction = (filt_best < filt_mid) ? -1 : 1;
125      filt_mid = filt_best;
126    }
127  }
128
129  return filt_best;
130}
131
132void vp9_pick_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
133                           LPF_PICK_METHOD method) {
134  VP9_COMMON *const cm = &cpi->common;
135  struct loopfilter *const lf = &cm->lf;
136
137  lf->sharpness_level = cm->frame_type == KEY_FRAME ? 0
138                                                    : cpi->oxcf.sharpness;
139
140  if (method == LPF_PICK_MINIMAL_LPF && lf->filter_level) {
141      lf->filter_level = 0;
142  } else if (method >= LPF_PICK_FROM_Q) {
143    const int min_filter_level = 0;
144    const int max_filter_level = get_max_filter_level(cpi);
145    const int q = vp9_ac_quant(cm->base_qindex, 0, cm->bit_depth);
146    // These values were determined by linear fitting the result of the
147    // searched level, filt_guess = q * 0.316206 + 3.87252
148    int filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 1015158, 18);
149    if (cm->frame_type == KEY_FRAME)
150      filt_guess -= 4;
151    lf->filter_level = clamp(filt_guess, min_filter_level, max_filter_level);
152  } else {
153    lf->filter_level = search_filter_level(sd, cpi,
154                                           method == LPF_PICK_FROM_SUBIMAGE);
155  }
156}
157