Libav
vf_interlace.c
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1 /*
2  * This file is part of Libav.
3  *
4  * Libav is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * Libav is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License along
15  * with Libav; if not, write to the Free Software Foundation, Inc.,
16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
17  */
18 
24 #include "libavutil/common.h"
25 #include "libavutil/opt.h"
26 #include "libavutil/imgutils.h"
27 #include "libavutil/avassert.h"
28 
29 #include "formats.h"
30 #include "avfilter.h"
31 #include "internal.h"
32 #include "video.h"
33 
34 enum ScanMode {
35  MODE_TFF = 0,
36  MODE_BFF = 1,
37 };
38 
39 enum FieldType {
42 };
43 
44 typedef struct {
45  const AVClass *class;
46  enum ScanMode scan; // top or bottom field first scanning
47  int lowpass; // enable or disable low pass filterning
48  AVFrame *cur, *next; // the two frames from which the new one is obtained
49  int got_output; // signal an output frame is reday to request_frame()
51 
52 #define OFFSET(x) offsetof(InterlaceContext, x)
53 #define V AV_OPT_FLAG_VIDEO_PARAM
54 static const AVOption options[] = {
55  { "scan", "scanning mode", OFFSET(scan),
56  AV_OPT_TYPE_INT, {.i64 = MODE_TFF }, 0, 1, .flags = V, .unit = "scan" },
57  { "tff", "top field first", 0,
58  AV_OPT_TYPE_CONST, {.i64 = MODE_TFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
59  { "bff", "bottom field first", 0,
60  AV_OPT_TYPE_CONST, {.i64 = MODE_BFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
61  { "lowpass", "enable vertical low-pass filter", OFFSET(lowpass),
62  AV_OPT_TYPE_INT, {.i64 = 1 }, 0, 1, .flags = V },
63  { NULL }
64 };
65 
66 static const AVClass class = {
67  .class_name = "interlace filter",
68  .item_name = av_default_item_name,
69  .option = options,
71 };
72 
73 
74 static const enum AVPixelFormat formats_supported[] = {
79 };
80 
82 {
84  return 0;
85 }
86 
87 static av_cold void uninit(AVFilterContext *ctx)
88 {
89  InterlaceContext *s = ctx->priv;
90 
91  av_frame_free(&s->cur);
92  av_frame_free(&s->next);
93 
94  av_opt_free(s);
95 }
96 
97 static int config_out_props(AVFilterLink *outlink)
98 {
99  AVFilterContext *ctx = outlink->src;
100  AVFilterLink *inlink = outlink->src->inputs[0];
101  InterlaceContext *s = ctx->priv;
102 
103  if (inlink->h < 2) {
104  av_log(ctx, AV_LOG_ERROR, "input video height is too small\n");
105  return AVERROR_INVALIDDATA;
106  }
107  // same input size
108  outlink->w = inlink->w;
109  outlink->h = inlink->h;
110  outlink->time_base = inlink->time_base;
111  // half framerate
112  outlink->time_base.num *= 2;
113 
114  av_log(ctx, AV_LOG_VERBOSE, "%s interlacing %s lowpass filter\n",
115  s->scan == MODE_TFF ? "tff" : "bff", (s->lowpass) ? "with" : "without");
116 
117  return 0;
118 }
119 
120 static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
121  AVFilterLink *inlink, enum FieldType field_type,
122  int lowpass)
123 {
124  const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
125  int vsub = desc->log2_chroma_h;
126  int plane, i, j;
127 
128  for (plane = 0; plane < desc->nb_components; plane++) {
129  int lines = (plane == 1 || plane == 2) ? -(-inlink->h) >> vsub : inlink->h;
130  int linesize = av_image_get_linesize(inlink->format, inlink->w, plane);
131  uint8_t *dstp = dst_frame->data[plane];
132  const uint8_t *srcp = src_frame->data[plane];
133 
134  av_assert0(linesize >= 0);
135 
136  lines = (lines + (field_type == FIELD_UPPER)) / 2;
137  if (field_type == FIELD_LOWER)
138  srcp += src_frame->linesize[plane];
139  if (field_type == FIELD_LOWER)
140  dstp += dst_frame->linesize[plane];
141  if (lowpass) {
142  int srcp_linesize = src_frame->linesize[plane] * 2;
143  int dstp_linesize = dst_frame->linesize[plane] * 2;
144  for (j = lines; j > 0; j--) {
145  const uint8_t *srcp_above = srcp - src_frame->linesize[plane];
146  const uint8_t *srcp_below = srcp + src_frame->linesize[plane];
147  if (j == lines)
148  srcp_above = srcp; // there is no line above
149  if (j == 1)
150  srcp_below = srcp; // there is no line below
151  for (i = 0; i < linesize; i++) {
152  // this calculation is an integer representation of
153  // '0.5 * current + 0.25 * above + 0.25 * below'
154  // '1 +' is for rounding.
155  dstp[i] = (1 + srcp[i] + srcp[i] + srcp_above[i] + srcp_below[i]) >> 2;
156  }
157  dstp += dstp_linesize;
158  srcp += srcp_linesize;
159  }
160  } else {
161  av_image_copy_plane(dstp, dst_frame->linesize[plane] * 2,
162  srcp, src_frame->linesize[plane] * 2,
163  linesize, lines);
164  }
165  }
166 }
167 
168 static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
169 {
170  AVFilterContext *ctx = inlink->dst;
171  AVFilterLink *outlink = ctx->outputs[0];
172  InterlaceContext *s = ctx->priv;
173  AVFrame *out;
174  int tff, ret;
175 
176  av_frame_free(&s->cur);
177  s->cur = s->next;
178  s->next = buf;
179 
180  /* we need at least two frames */
181  if (!s->cur || !s->next)
182  return 0;
183 
184  if (s->cur->interlaced_frame) {
185  av_log(ctx, AV_LOG_WARNING,
186  "video is already interlaced, adjusting framerate only\n");
187  out = av_frame_clone(s->cur);
188  if (!out)
189  return AVERROR(ENOMEM);
190  out->pts /= 2; // adjust pts to new framerate
191  ret = ff_filter_frame(outlink, out);
192  s->got_output = 1;
193  return ret;
194  }
195 
196  tff = (s->scan == MODE_TFF);
197  out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
198  if (!out)
199  return AVERROR(ENOMEM);
200 
201  av_frame_copy_props(out, s->cur);
202  out->interlaced_frame = 1;
203  out->top_field_first = tff;
204  out->pts /= 2; // adjust pts to new framerate
205 
206  /* copy upper/lower field from cur */
207  copy_picture_field(s->cur, out, inlink, tff ? FIELD_UPPER : FIELD_LOWER, s->lowpass);
208  av_frame_free(&s->cur);
209 
210  /* copy lower/upper field from next */
211  copy_picture_field(s->next, out, inlink, tff ? FIELD_LOWER : FIELD_UPPER, s->lowpass);
212  av_frame_free(&s->next);
213 
214  ret = ff_filter_frame(outlink, out);
215  s->got_output = 1;
216 
217  return ret;
218 }
219 
220 static int request_frame(AVFilterLink *outlink)
221 {
222  AVFilterContext *ctx = outlink->src;
223  InterlaceContext *s = ctx->priv;
224  int ret = 0;
225 
226  s->got_output = 0;
227  while (ret >= 0 && !s->got_output)
228  ret = ff_request_frame(ctx->inputs[0]);
229 
230  return ret;
231 }
232 
233 static const AVFilterPad inputs[] = {
234  {
235  .name = "default",
236  .type = AVMEDIA_TYPE_VIDEO,
237  .filter_frame = filter_frame,
238  },
239  { NULL }
240 };
241 
242 static const AVFilterPad outputs[] = {
243  {
244  .name = "default",
245  .type = AVMEDIA_TYPE_VIDEO,
246  .config_props = config_out_props,
247  .request_frame = request_frame,
248  },
249  { NULL }
250 };
251 
253  .name = "interlace",
254  .description = NULL_IF_CONFIG_SMALL("Convert progressive video into interlaced."),
255  .uninit = uninit,
256 
257  .priv_class = &class,
258  .priv_size = sizeof(InterlaceContext),
260 
261  .inputs = inputs,
262  .outputs = outputs,
263 };
264