FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
vf_qp.c
Go to the documentation of this file.
1 /*
2  * Copyright (C) 2004 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include <math.h>
22 #include "libavutil/eval.h"
23 #include "libavutil/imgutils.h"
24 #include "libavutil/pixdesc.h"
25 #include "libavutil/opt.h"
26 #include "avfilter.h"
27 #include "formats.h"
28 #include "internal.h"
29 #include "video.h"
30 
31 typedef struct QPContext {
32  const AVClass *class;
33  char *qp_expr_str;
34  int8_t lut[257];
35  int h, qstride;
36 } QPContext;
37 
38 #define OFFSET(x) offsetof(QPContext, x)
39 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
40 
41 static const AVOption qp_options[] = {
42  { "qp", "set qp expression", OFFSET(qp_expr_str), AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0, FLAGS },
43  { NULL }
44 };
45 
47 
48 static int config_input(AVFilterLink *inlink)
49 {
50  AVFilterContext *ctx = inlink->dst;
51  QPContext *s = ctx->priv;
52  int i;
53 
54  if (!s->qp_expr_str)
55  return 0;
56 
57  s->h = (inlink->h + 15) >> 4;
58  s->qstride = (inlink->w + 15) >> 4;
59  for (i = -129; i < 128; i++) {
60  double var_values[] = { i != -129, i, 0 };
61  static const char *var_names[] = { "known", "qp", NULL };
62  double temp_val;
63  int ret;
64 
65  ret = av_expr_parse_and_eval(&temp_val, s->qp_expr_str,
66  var_names, var_values,
67  NULL, NULL, NULL, NULL, 0, 0, ctx);
68  if (ret < 0)
69  return ret;
70 
71  s->lut[i + 129] = lrintf(temp_val);
72  }
73 
74  return 0;
75 }
76 
77 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
78 {
79  AVFilterContext *ctx = inlink->dst;
80  AVFilterLink *outlink = ctx->outputs[0];
81  QPContext *s = ctx->priv;
82  AVBufferRef *out_qp_table_buf;
83  AVFrame *out;
84  const int8_t *in_qp_table;
85  int type, stride, ret;
86 
87  if (!s->qp_expr_str || ctx->is_disabled)
88  return ff_filter_frame(outlink, in);
89 
90  out_qp_table_buf = av_buffer_alloc(s->h * s->qstride);
91  if (!out_qp_table_buf) {
92  ret = AVERROR(ENOMEM);
93  goto fail;
94  }
95 
96  out = av_frame_clone(in);
97  if (!out) {
98  ret = AVERROR(ENOMEM);
99  goto fail;
100  }
101 
102  in_qp_table = av_frame_get_qp_table(in, &stride, &type);
103  av_frame_set_qp_table(out, out_qp_table_buf, s->qstride, type);
104 
105  if (in_qp_table) {
106  int y, x;
107 
108  for (y = 0; y < s->h; y++)
109  for (x = 0; x < s->qstride; x++)
110  out_qp_table_buf->data[x + s->qstride * y] = s->lut[129 +
111  ((int8_t)in_qp_table[x + stride * y])];
112  } else {
113  int y, x, qp = s->lut[0];
114 
115  for (y = 0; y < s->h; y++)
116  for (x = 0; x < s->qstride; x++)
117  out_qp_table_buf->data[x + s->qstride * y] = qp;
118  }
119 
120  ret = ff_filter_frame(outlink, out);
121 fail:
122  av_frame_free(&in);
123  return ret;
124 }
125 
126 static const AVFilterPad qp_inputs[] = {
127  {
128  .name = "default",
129  .type = AVMEDIA_TYPE_VIDEO,
130  .filter_frame = filter_frame,
131  .config_props = config_input,
132  },
133  { NULL }
134 };
135 
136 static const AVFilterPad qp_outputs[] = {
137  {
138  .name = "default",
139  .type = AVMEDIA_TYPE_VIDEO,
140  },
141  { NULL }
142 };
143 
145  .name = "qp",
146  .description = NULL_IF_CONFIG_SMALL("Change video quantization parameters."),
147  .priv_size = sizeof(QPContext),
148  .inputs = qp_inputs,
149  .outputs = qp_outputs,
150  .priv_class = &qp_class,
152 };