FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
filtering_video.c
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2010 Nicolas George
3  * Copyright (c) 2011 Stefano Sabatini
4  *
5  * Permission is hereby granted, free of charge, to any person obtaining a copy
6  * of this software and associated documentation files (the "Software"), to deal
7  * in the Software without restriction, including without limitation the rights
8  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9  * copies of the Software, and to permit persons to whom the Software is
10  * furnished to do so, subject to the following conditions:
11  *
12  * The above copyright notice and this permission notice shall be included in
13  * all copies or substantial portions of the Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21  * THE SOFTWARE.
22  */
23 
24 /**
25  * @file
26  * API example for decoding and filtering
27  * @example filtering_video.c
28  */
29 
30 #define _XOPEN_SOURCE 600 /* for usleep */
31 #include <unistd.h>
32 
33 #include <libavcodec/avcodec.h>
34 #include <libavformat/avformat.h>
36 #include <libavfilter/avcodec.h>
37 #include <libavfilter/buffersink.h>
38 #include <libavfilter/buffersrc.h>
39 #include <libavutil/opt.h>
40 
41 const char *filter_descr = "scale=78:24";
42 
48 static int video_stream_index = -1;
49 static int64_t last_pts = AV_NOPTS_VALUE;
50 
51 static int open_input_file(const char *filename)
52 {
53  int ret;
54  AVCodec *dec;
55 
56  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
57  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
58  return ret;
59  }
60 
61  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
62  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
63  return ret;
64  }
65 
66  /* select the video stream */
67  ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
68  if (ret < 0) {
69  av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
70  return ret;
71  }
73  dec_ctx = fmt_ctx->streams[video_stream_index]->codec;
74  av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
75 
76  /* init the video decoder */
77  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
78  av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
79  return ret;
80  }
81 
82  return 0;
83 }
84 
85 static int init_filters(const char *filters_descr)
86 {
87  char args[512];
88  int ret = 0;
89  AVFilter *buffersrc = avfilter_get_by_name("buffer");
90  AVFilter *buffersink = avfilter_get_by_name("buffersink");
93  AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
94  enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
95 
96  filter_graph = avfilter_graph_alloc();
97  if (!outputs || !inputs || !filter_graph) {
98  ret = AVERROR(ENOMEM);
99  goto end;
100  }
101 
102  /* buffer video source: the decoded frames from the decoder will be inserted here. */
103  snprintf(args, sizeof(args),
104  "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
105  dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
106  time_base.num, time_base.den,
107  dec_ctx->sample_aspect_ratio.num, dec_ctx->sample_aspect_ratio.den);
108 
109  ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
110  args, NULL, filter_graph);
111  if (ret < 0) {
112  av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
113  goto end;
114  }
115 
116  /* buffer video sink: to terminate the filter chain. */
117  ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
118  NULL, NULL, filter_graph);
119  if (ret < 0) {
120  av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
121  goto end;
122  }
123 
124  ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
126  if (ret < 0) {
127  av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
128  goto end;
129  }
130 
131  /* Endpoints for the filter graph. */
132  outputs->name = av_strdup("in");
133  outputs->filter_ctx = buffersrc_ctx;
134  outputs->pad_idx = 0;
135  outputs->next = NULL;
136 
137  inputs->name = av_strdup("out");
138  inputs->filter_ctx = buffersink_ctx;
139  inputs->pad_idx = 0;
140  inputs->next = NULL;
141 
142  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
143  &inputs, &outputs, NULL)) < 0)
144  goto end;
145 
146  if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
147  goto end;
148 
149 end:
150  avfilter_inout_free(&inputs);
151  avfilter_inout_free(&outputs);
152 
153  return ret;
154 }
155 
156 static void display_frame(const AVFrame *frame, AVRational time_base)
157 {
158  int x, y;
159  uint8_t *p0, *p;
160  int64_t delay;
161 
162  if (frame->pts != AV_NOPTS_VALUE) {
163  if (last_pts != AV_NOPTS_VALUE) {
164  /* sleep roughly the right amount of time;
165  * usleep is in microseconds, just like AV_TIME_BASE. */
166  delay = av_rescale_q(frame->pts - last_pts,
167  time_base, AV_TIME_BASE_Q);
168  if (delay > 0 && delay < 1000000)
169  usleep(delay);
170  }
171  last_pts = frame->pts;
172  }
173 
174  /* Trivial ASCII grayscale display. */
175  p0 = frame->data[0];
176  puts("\033c");
177  for (y = 0; y < frame->height; y++) {
178  p = p0;
179  for (x = 0; x < frame->width; x++)
180  putchar(" .-+#"[*(p++) / 52]);
181  putchar('\n');
182  p0 += frame->linesize[0];
183  }
184  fflush(stdout);
185 }
186 
187 int main(int argc, char **argv)
188 {
189  int ret;
190  AVPacket packet;
192  AVFrame *filt_frame = av_frame_alloc();
193  int got_frame;
194 
195  if (!frame || !filt_frame) {
196  perror("Could not allocate frame");
197  exit(1);
198  }
199  if (argc != 2) {
200  fprintf(stderr, "Usage: %s file\n", argv[0]);
201  exit(1);
202  }
203 
204  av_register_all();
206 
207  if ((ret = open_input_file(argv[1])) < 0)
208  goto end;
209  if ((ret = init_filters(filter_descr)) < 0)
210  goto end;
211 
212  /* read all packets */
213  while (1) {
214  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
215  break;
216 
217  if (packet.stream_index == video_stream_index) {
218  got_frame = 0;
219  ret = avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
220  if (ret < 0) {
221  av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
222  break;
223  }
224 
225  if (got_frame) {
226  frame->pts = av_frame_get_best_effort_timestamp(frame);
227 
228  /* push the decoded frame into the filtergraph */
229  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
230  av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
231  break;
232  }
233 
234  /* pull filtered frames from the filtergraph */
235  while (1) {
236  ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
237  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
238  break;
239  if (ret < 0)
240  goto end;
241  display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
242  av_frame_unref(filt_frame);
243  }
244  av_frame_unref(frame);
245  }
246  }
247  av_free_packet(&packet);
248  }
249 end:
250  avfilter_graph_free(&filter_graph);
251  avcodec_close(dec_ctx);
252  avformat_close_input(&fmt_ctx);
253  av_frame_free(&frame);
254  av_frame_free(&filt_frame);
255 
256  if (ret < 0 && ret != AVERROR_EOF) {
257  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
258  exit(1);
259  }
260 
261  exit(0);
262 }