FFmpeg 4.4.5
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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#include <stdio.h>
33#include <stdlib.h>
34
35#include <libavcodec/avcodec.h>
39#include <libavutil/opt.h>
40
41const 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
51static int video_stream_index = -1;
52static int64_t last_pts = AV_NOPTS_VALUE;
53
54static int open_input_file(const char *filename)
55{
56 int ret;
57 AVCodec *dec;
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 */
70 ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
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
92static 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");
101 enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
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",
125 NULL, NULL, filter_graph);
126 if (ret < 0) {
127 av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
128 goto end;
129 }
130
131 ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
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
169 if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
170 goto end;
171
172end:
173 avfilter_inout_free(&inputs);
174 avfilter_inout_free(&outputs);
175
176 return ret;
177}
178
179static 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
210int 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
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
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) {
265 ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
266 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
267 break;
268 if (ret < 0)
269 goto end;
271 av_frame_unref(filt_frame);
272 }
274 }
275 }
276 av_packet_unref(&packet);
277 }
278end:
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}
Libavcodec external API header.
Main libavformat public API header.
int main(int argc, char *argv[])
memory buffer sink API for audio and video
Memory buffer source API.
static AVFormatContext * fmt_ctx
static AVFrame * frame
AVFilterGraph * filter_graph
AVFilterContext * buffersink_ctx
static const char * filter_descr
AVFilterContext * buffersrc_ctx
static int open_input_file(const char *filename)
static AVCodecContext * dec_ctx
static void display_frame(const AVFrame *frame, AVRational time_base)
static int video_stream_index
static int64_t last_pts
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition opt.h:560
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type, int wanted_stream_nb, int related_stream, AVCodec **decoder_ret, int flags)
Find the "best" stream in the file.
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
int avformat_open_input(AVFormatContext **ps, const char *url, ff_const59 AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
int av_buffersink_get_frame(AVFilterContext *ctx, AVFrame *frame)
Get a frame with filtered data from sink and put it in frame.
av_warn_unused_result int av_buffersrc_add_frame_flags(AVFilterContext *buffer_src, AVFrame *frame, int flags)
Add a frame to the buffer source.
@ AV_BUFFERSRC_FLAG_KEEP_REF
Keep a reference to the frame.
Definition buffersrc.h:53
int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx)
Check validity and configure all the links and formats in the graph.
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
void avfilter_inout_free(AVFilterInOut **inout)
Free the supplied list of AVFilterInOut and set *inout to NULL.
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.
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
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.
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
#define AVERROR_EOF
End of file.
Definition error.h:55
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition error.h:119
#define AVERROR(e)
Definition error.h:43
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition log.h:194
void av_log(void *avcl, int level, const char *fmt,...) av_printf_format(3
Send the specified message to the log if the level is less than or equal to the current av_log_level.
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const
Rescale a 64-bit integer by 2 rational numbers.
char * av_strdup(const char *s) av_malloc_attrib
Duplicate a string.
@ AVMEDIA_TYPE_VIDEO
Definition avutil.h:201
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition avutil.h:248
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition avutil.h:260
#define av_opt_set_int_list(obj, name, val, term, flags)
Set a binary option to an integer list.
Definition opt.h:727
AVOptions.
AVPixelFormat
Pixel format.
Definition pixfmt.h:64
@ AV_PIX_FMT_NONE
Definition pixfmt.h:65
@ AV_PIX_FMT_GRAY8
Y , 8bpp.
Definition pixfmt.h:74
main external API structure.
Definition avcodec.h:536
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition avcodec.h:746
int width
picture width / height.
Definition avcodec.h:709
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:915
AVCodec.
Definition codec.h:197
An instance of a filter.
Definition avfilter.h:341
AVFilterLink ** inputs
array of pointers to input links
Definition avfilter.h:349
A linked-list of the inputs/outputs of the filter chain.
Definition avfilter.h:1013
AVFilterContext * filter_ctx
filter context associated to this input/output
Definition avfilter.h:1018
int pad_idx
index of the filt_ctx pad to use for linking
Definition avfilter.h:1021
char * name
unique name for this input/output in the list
Definition avfilter.h:1015
struct AVFilterInOut * next
next input/input in the list, NULL if this is the last
Definition avfilter.h:1024
Filter definition.
Definition avfilter.h:145
Format I/O context.
Definition avformat.h:1232
AVStream ** streams
A list of all streams in the file.
Definition avformat.h:1300
This structure describes decoded (raw) audio or video data.
Definition frame.h:318
int64_t pts
Presentation timestamp in time_base units (time when frame should be shown to user).
Definition frame.h:411
int64_t best_effort_timestamp
frame timestamp estimated using various heuristics, in stream time base
Definition frame.h:582
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition frame.h:332
int width
Definition frame.h:376
int height
Definition frame.h:376
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
Definition frame.h:349
This structure stores compressed data.
Definition packet.h:346
int stream_index
Definition packet.h:371
Rational number (pair of numerator and denominator).
Definition rational.h:58
int num
Numerator.
Definition rational.h:59
int den
Denominator.
Definition rational.h:60
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition avformat.h:1038
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition avformat.h:902
static int init_filters(void)