FFmpeg
filtering_video.c
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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 #include <stdio.h>
33 #include <stdlib.h>
34 
35 #include <libavcodec/avcodec.h>
36 #include <libavformat/avformat.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,transpose=cclock";
42 /* other way:
43  scale=78:24 [scl]; [scl] transpose=cclock // assumes "[in]" and "[out]" to be input output pads respectively
44  */
45 
51 static int video_stream_index = -1;
52 static int64_t last_pts = AV_NOPTS_VALUE;
53 
54 static int open_input_file(const char *filename)
55 {
56  const AVCodec *dec;
57  int ret;
58 
59  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
60  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
61  return ret;
62  }
63 
64  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
65  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
66  return ret;
67  }
68 
69  /* select the video stream */
71  if (ret < 0) {
72  av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
73  return ret;
74  }
76 
77  /* create decoding context */
79  if (!dec_ctx)
80  return AVERROR(ENOMEM);
82 
83  /* init the video decoder */
84  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
85  av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
86  return ret;
87  }
88 
89  return 0;
90 }
91 
92 static int init_filters(const char *filters_descr)
93 {
94  char args[512];
95  int ret = 0;
96  const AVFilter *buffersrc = avfilter_get_by_name("buffer");
97  const AVFilter *buffersink = avfilter_get_by_name("buffersink");
102 
104  if (!outputs || !inputs || !filter_graph) {
105  ret = AVERROR(ENOMEM);
106  goto end;
107  }
108 
109  /* buffer video source: the decoded frames from the decoder will be inserted here. */
110  snprintf(args, sizeof(args),
111  "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
113  time_base.num, time_base.den,
115 
116  ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
117  args, NULL, filter_graph);
118  if (ret < 0) {
119  av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
120  goto end;
121  }
122 
123  /* buffer video sink: to terminate the filter chain. */
124  ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
126  if (ret < 0) {
127  av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
128  goto end;
129  }
130 
133  if (ret < 0) {
134  av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
135  goto end;
136  }
137 
138  /*
139  * Set the endpoints for the filter graph. The filter_graph will
140  * be linked to the graph described by filters_descr.
141  */
142 
143  /*
144  * The buffer source output must be connected to the input pad of
145  * the first filter described by filters_descr; since the first
146  * filter input label is not specified, it is set to "in" by
147  * default.
148  */
149  outputs->name = av_strdup("in");
150  outputs->filter_ctx = buffersrc_ctx;
151  outputs->pad_idx = 0;
152  outputs->next = NULL;
153 
154  /*
155  * The buffer sink input must be connected to the output pad of
156  * the last filter described by filters_descr; since the last
157  * filter output label is not specified, it is set to "out" by
158  * default.
159  */
160  inputs->name = av_strdup("out");
161  inputs->filter_ctx = buffersink_ctx;
162  inputs->pad_idx = 0;
163  inputs->next = NULL;
164 
165  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
166  &inputs, &outputs, NULL)) < 0)
167  goto end;
168 
170  goto end;
171 
172 end:
175 
176  return ret;
177 }
178 
179 static void display_frame(const AVFrame *frame, AVRational time_base)
180 {
181  int x, y;
182  uint8_t *p0, *p;
183  int64_t delay;
184 
185  if (frame->pts != AV_NOPTS_VALUE) {
186  if (last_pts != AV_NOPTS_VALUE) {
187  /* sleep roughly the right amount of time;
188  * usleep is in microseconds, just like AV_TIME_BASE. */
189  delay = av_rescale_q(frame->pts - last_pts,
190  time_base, AV_TIME_BASE_Q);
191  if (delay > 0 && delay < 1000000)
192  usleep(delay);
193  }
194  last_pts = frame->pts;
195  }
196 
197  /* Trivial ASCII grayscale display. */
198  p0 = frame->data[0];
199  puts("\033c");
200  for (y = 0; y < frame->height; y++) {
201  p = p0;
202  for (x = 0; x < frame->width; x++)
203  putchar(" .-+#"[*(p++) / 52]);
204  putchar('\n');
205  p0 += frame->linesize[0];
206  }
207  fflush(stdout);
208 }
209 
210 int main(int argc, char **argv)
211 {
212  int ret;
213  AVPacket packet;
214  AVFrame *frame;
215  AVFrame *filt_frame;
216 
217  if (argc != 2) {
218  fprintf(stderr, "Usage: %s file\n", argv[0]);
219  exit(1);
220  }
221 
222  frame = av_frame_alloc();
223  filt_frame = av_frame_alloc();
224  if (!frame || !filt_frame) {
225  perror("Could not allocate frame");
226  exit(1);
227  }
228 
229  if ((ret = open_input_file(argv[1])) < 0)
230  goto end;
231  if ((ret = init_filters(filter_descr)) < 0)
232  goto end;
233 
234  /* read all packets */
235  while (1) {
236  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
237  break;
238 
239  if (packet.stream_index == video_stream_index) {
240  ret = avcodec_send_packet(dec_ctx, &packet);
241  if (ret < 0) {
242  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
243  break;
244  }
245 
246  while (ret >= 0) {
248  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
249  break;
250  } else if (ret < 0) {
251  av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
252  goto end;
253  }
254 
255  frame->pts = frame->best_effort_timestamp;
256 
257  /* push the decoded frame into the filtergraph */
259  av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
260  break;
261  }
262 
263  /* pull filtered frames from the filtergraph */
264  while (1) {
266  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
267  break;
268  if (ret < 0)
269  goto end;
270  display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
271  av_frame_unref(filt_frame);
272  }
274  }
275  }
276  av_packet_unref(&packet);
277  }
278 end:
283  av_frame_free(&filt_frame);
284 
285  if (ret < 0 && ret != AVERROR_EOF) {
286  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
287  exit(1);
288  }
289 
290  exit(0);
291 }
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:403
AVCodec
AVCodec.
Definition: codec.h:197
fmt_ctx
static AVFormatContext * fmt_ctx
Definition: filtering_video.c:46
AVPixelFormat
AVPixelFormat
Pixel format.
Definition: pixfmt.h:64
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
opt.h
last_pts
static int64_t last_pts
Definition: filtering_video.c:52
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:55
AV_TIME_BASE_Q
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition: avutil.h:260
av_opt_set_int_list
#define av_opt_set_int_list(obj, name, val, term, flags)
Set a binary option to an integer list.
Definition: opt.h:714
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:111
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:303
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1174
main
int main(int argc, char **argv)
Definition: filtering_video.c:210
av_read_frame
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1665
avfilter_graph_free
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
Definition: avfiltergraph.c:120
av_find_best_stream
int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type, int wanted_stream_nb, int related_stream, const AVCodec **decoder_ret, int flags)
Find the "best" stream in the file.
Definition: utils.c:4118
avformat_close_input
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: utils.c:4344
avfilter_graph_create_filter
int avfilter_graph_create_filter(AVFilterContext **filt_ctx, const AVFilter *filt, const char *name, const char *args, void *opaque, AVFilterGraph *graph_ctx)
Create and add a filter instance into an existing graph.
Definition: avfiltergraph.c:139
avfilter_graph_alloc
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:83
AVRational::num
int num
Numerator.
Definition: rational.h:59
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:98
avfilter_inout_free
void avfilter_inout_free(AVFilterInOut **inout)
Free the supplied list of AVFilterInOut and set *inout to NULL.
Definition: graphparser.c:212
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:181
inputs
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several inputs
Definition: filter_design.txt:243
filter_descr
const char * filter_descr
Definition: filtering_video.c:41
avformat_open_input
int avformat_open_input(AVFormatContext **ps, const char *url, const AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: utils.c:481
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:141
av_buffersink_get_frame
int attribute_align_arg av_buffersink_get_frame(AVFilterContext *ctx, AVFrame *frame)
Get a frame with filtered data from sink and put it in frame.
Definition: buffersink.c:88
avcodec_receive_frame
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:628
outputs
static const AVFilterPad outputs[]
Definition: af_acontrast.c:203
pix_fmts
static enum AVPixelFormat pix_fmts[]
Definition: libkvazaar.c:289
av_rescale_q
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:142
AVFormatContext
Format I/O context.
Definition: avformat.h:1106
avfilter_get_by_name
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: allfilters.c:547
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:979
avfilter_graph_config
int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx)
Check validity and configure all the links and formats in the graph.
Definition: avfiltergraph.c:1215
AVStream::time_base
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition: avformat.h:855
NULL
#define NULL
Definition: coverity.c:32
avcodec_free_context
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
Definition: options.c:156
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
AVFilterContext::inputs
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:341
avfilter_inout_alloc
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
Definition: graphparser.c:207
buffersrc_ctx
AVFilterContext * buffersrc_ctx
Definition: filtering_video.c:49
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: avcodec.c:135
AVFilterGraph
Definition: avfilter.h:798
AV_PIX_FMT_GRAY8
@ AV_PIX_FMT_GRAY8
Y , 8bpp.
Definition: pixfmt.h:74
avformat_find_stream_info
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
Definition: utils.c:3543
av_err2str
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:119
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
open_input_file
static int open_input_file(const char *filename)
Definition: filtering_video.c:54
AV_OPT_SEARCH_CHILDREN
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition: opt.h:560
video_stream_index
static int video_stream_index
Definition: filtering_video.c:51
buffersink.h
filter_graph
AVFilterGraph * filter_graph
Definition: filtering_video.c:50
avcodec_send_packet
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:565
buffersink_ctx
AVFilterContext * buffersink_ctx
Definition: filtering_video.c:48
avfilter_graph_parse_ptr
int avfilter_graph_parse_ptr(AVFilterGraph *graph, const char *filters, AVFilterInOut **inputs, AVFilterInOut **outputs, void *log_ctx)
Add a graph described by a string to a graph.
Definition: graphparser.c:549
avcodec_parameters_to_context
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
Definition: codec_par.c:147
av_buffersrc_add_frame_flags
int attribute_align_arg av_buffersrc_add_frame_flags(AVFilterContext *ctx, AVFrame *frame, int flags)
Add a frame to the buffer source.
Definition: buffersrc.c:166
AV_BUFFERSRC_FLAG_KEEP_REF
@ AV_BUFFERSRC_FLAG_KEEP_REF
Keep a reference to the frame.
Definition: buffersrc.h:53
av_frame_unref
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:436
AVFilterPad::name
const char * name
Pad name.
Definition: internal.h:60
AVCodecContext::height
int height
Definition: avcodec.h:674
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:711
avcodec.h
AVFilter
Filter definition.
Definition: avfilter.h:145
ret
ret
Definition: filter_design.txt:187
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
init_filters
static int init_filters(const char *filters_descr)
Definition: filtering_video.c:92
avformat.h
AVCodecContext
main external API structure.
Definition: avcodec.h:501
AVRational::den
int den
Denominator.
Definition: rational.h:60
AV_PIX_FMT_NONE
@ AV_PIX_FMT_NONE
Definition: pixfmt.h:65
display_frame
static void display_frame(const AVFrame *frame, AVRational time_base)
Definition: filtering_video.c:179
AVPacket::stream_index
int stream_index
Definition: packet.h:367
AVFilterContext
An instance of a filter.
Definition: avfilter.h:333
av_strdup
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:259
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
AVPacket
This structure stores compressed data.
Definition: packet.h:342
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:674
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
AVFilterInOut
A linked-list of the inputs/outputs of the filter chain.
Definition: avfilter.h:958
snprintf
#define snprintf
Definition: snprintf.h:34
buffersrc.h
AVCodecContext::sample_aspect_ratio
AVRational sample_aspect_ratio
sample aspect ratio (0 if unknown) That is the width of a pixel divided by the height of the pixel.
Definition: avcodec.h:859
dec_ctx
static AVCodecContext * dec_ctx
Definition: filtering_video.c:47