2 * copyright (c) 2013 Andrew Kelley
4 * This file is part of FFmpeg.
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.
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.
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
23 * libavfilter API usage example.
25 * @example filter_audio.c
26 * This example will generate a sine wave audio,
27 * pass it through a simple filter chain, and then compute the MD5 checksum of
30 * The filter chain it uses is:
31 * (input) -> abuffer -> volume -> aformat -> abuffersink -> (output)
33 * abuffer: This provides the endpoint where you can feed the decoded samples.
34 * volume: In this example we hardcode it to 0.90.
35 * aformat: This converts the samples to the samplefreq, channel layout,
36 * and sample format required by the audio device.
37 * abuffersink: This provides the endpoint where you can read the samples after
38 * they have passed through the filter chain.
46 #include "libavutil/channel_layout.h"
47 #include "libavutil/md5.h"
48 #include "libavutil/opt.h"
49 #include "libavutil/samplefmt.h"
51 #include "libavfilter/avfilter.h"
52 #include "libavfilter/buffersink.h"
53 #include "libavfilter/buffersrc.h"
55 #define INPUT_SAMPLERATE 48000
56 #define INPUT_FORMAT AV_SAMPLE_FMT_FLTP
57 #define INPUT_CHANNEL_LAYOUT AV_CH_LAYOUT_5POINT0
59 #define VOLUME_VAL 0.90
61 static int init_filter_graph(AVFilterGraph **graph, AVFilterContext **src,
62 AVFilterContext **sink)
64 AVFilterGraph *filter_graph;
65 AVFilterContext *abuffer_ctx;
67 AVFilterContext *volume_ctx;
69 AVFilterContext *aformat_ctx;
71 AVFilterContext *abuffersink_ctx;
72 AVFilter *abuffersink;
74 AVDictionary *options_dict = NULL;
75 uint8_t options_str[1024];
76 uint8_t ch_layout[64];
80 /* Create a new filtergraph, which will contain all the filters. */
81 filter_graph = avfilter_graph_alloc();
83 fprintf(stderr, "Unable to create filter graph.\n");
84 return AVERROR(ENOMEM);
87 /* Create the abuffer filter;
88 * it will be used for feeding the data into the graph. */
89 abuffer = avfilter_get_by_name("abuffer");
91 fprintf(stderr, "Could not find the abuffer filter.\n");
92 return AVERROR_FILTER_NOT_FOUND;
95 abuffer_ctx = avfilter_graph_alloc_filter(filter_graph, abuffer, "src");
97 fprintf(stderr, "Could not allocate the abuffer instance.\n");
98 return AVERROR(ENOMEM);
101 /* Set the filter options through the AVOptions API. */
102 av_get_channel_layout_string(ch_layout, sizeof(ch_layout), 0, INPUT_CHANNEL_LAYOUT);
103 av_opt_set (abuffer_ctx, "channel_layout", ch_layout, AV_OPT_SEARCH_CHILDREN);
104 av_opt_set (abuffer_ctx, "sample_fmt", av_get_sample_fmt_name(INPUT_FORMAT), AV_OPT_SEARCH_CHILDREN);
105 av_opt_set_q (abuffer_ctx, "time_base", (AVRational){ 1, INPUT_SAMPLERATE }, AV_OPT_SEARCH_CHILDREN);
106 av_opt_set_int(abuffer_ctx, "sample_rate", INPUT_SAMPLERATE, AV_OPT_SEARCH_CHILDREN);
108 /* Now initialize the filter; we pass NULL options, since we have already
109 * set all the options above. */
110 err = avfilter_init_str(abuffer_ctx, NULL);
112 fprintf(stderr, "Could not initialize the abuffer filter.\n");
116 /* Create volume filter. */
117 volume = avfilter_get_by_name("volume");
119 fprintf(stderr, "Could not find the volume filter.\n");
120 return AVERROR_FILTER_NOT_FOUND;
123 volume_ctx = avfilter_graph_alloc_filter(filter_graph, volume, "volume");
125 fprintf(stderr, "Could not allocate the volume instance.\n");
126 return AVERROR(ENOMEM);
129 /* A different way of passing the options is as key/value pairs in a
131 av_dict_set(&options_dict, "volume", AV_STRINGIFY(VOLUME_VAL), 0);
132 err = avfilter_init_dict(volume_ctx, &options_dict);
133 av_dict_free(&options_dict);
135 fprintf(stderr, "Could not initialize the volume filter.\n");
139 /* Create the aformat filter;
140 * it ensures that the output is of the format we want. */
141 aformat = avfilter_get_by_name("aformat");
143 fprintf(stderr, "Could not find the aformat filter.\n");
144 return AVERROR_FILTER_NOT_FOUND;
147 aformat_ctx = avfilter_graph_alloc_filter(filter_graph, aformat, "aformat");
149 fprintf(stderr, "Could not allocate the aformat instance.\n");
150 return AVERROR(ENOMEM);
153 /* A third way of passing the options is in a string of the form
154 * key1=value1:key2=value2.... */
155 snprintf(options_str, sizeof(options_str),
156 "sample_fmts=%s:sample_rates=%d:channel_layouts=0x%"PRIx64,
157 av_get_sample_fmt_name(AV_SAMPLE_FMT_S16), 44100,
158 (uint64_t)AV_CH_LAYOUT_STEREO);
159 err = avfilter_init_str(aformat_ctx, options_str);
161 av_log(NULL, AV_LOG_ERROR, "Could not initialize the aformat filter.\n");
165 /* Finally create the abuffersink filter;
166 * it will be used to get the filtered data out of the graph. */
167 abuffersink = avfilter_get_by_name("abuffersink");
169 fprintf(stderr, "Could not find the abuffersink filter.\n");
170 return AVERROR_FILTER_NOT_FOUND;
173 abuffersink_ctx = avfilter_graph_alloc_filter(filter_graph, abuffersink, "sink");
174 if (!abuffersink_ctx) {
175 fprintf(stderr, "Could not allocate the abuffersink instance.\n");
176 return AVERROR(ENOMEM);
179 /* This filter takes no options. */
180 err = avfilter_init_str(abuffersink_ctx, NULL);
182 fprintf(stderr, "Could not initialize the abuffersink instance.\n");
186 /* Connect the filters;
187 * in this simple case the filters just form a linear chain. */
188 err = avfilter_link(abuffer_ctx, 0, volume_ctx, 0);
190 err = avfilter_link(volume_ctx, 0, aformat_ctx, 0);
192 err = avfilter_link(aformat_ctx, 0, abuffersink_ctx, 0);
194 fprintf(stderr, "Error connecting filters\n");
198 /* Configure the graph. */
199 err = avfilter_graph_config(filter_graph, NULL);
201 av_log(NULL, AV_LOG_ERROR, "Error configuring the filter graph\n");
205 *graph = filter_graph;
207 *sink = abuffersink_ctx;
212 /* Do something useful with the filtered data: this simple
213 * example just prints the MD5 checksum of each plane to stdout. */
214 static int process_output(struct AVMD5 *md5, AVFrame *frame)
216 int planar = av_sample_fmt_is_planar(frame->format);
217 int channels = av_get_channel_layout_nb_channels(frame->channel_layout);
218 int planes = planar ? channels : 1;
219 int bps = av_get_bytes_per_sample(frame->format);
220 int plane_size = bps * frame->nb_samples * (planar ? 1 : channels);
223 for (i = 0; i < planes; i++) {
224 uint8_t checksum[16];
227 av_md5_sum(checksum, frame->extended_data[i], plane_size);
229 fprintf(stdout, "plane %d: 0x", i);
230 for (j = 0; j < sizeof(checksum); j++)
231 fprintf(stdout, "%02X", checksum[j]);
232 fprintf(stdout, "\n");
234 fprintf(stdout, "\n");
239 /* Construct a frame of audio data to be filtered;
240 * this simple example just synthesizes a sine wave. */
241 static int get_input(AVFrame *frame, int frame_num)
245 #define FRAME_SIZE 1024
247 /* Set up the frame properties and allocate the buffer for the data. */
248 frame->sample_rate = INPUT_SAMPLERATE;
249 frame->format = INPUT_FORMAT;
250 frame->channel_layout = INPUT_CHANNEL_LAYOUT;
251 frame->nb_samples = FRAME_SIZE;
252 frame->pts = frame_num * FRAME_SIZE;
254 err = av_frame_get_buffer(frame, 0);
258 /* Fill the data for each channel. */
259 for (i = 0; i < 5; i++) {
260 float *data = (float*)frame->extended_data[i];
262 for (j = 0; j < frame->nb_samples; j++)
263 data[j] = sin(2 * M_PI * (frame_num + j) * (i + 1) / FRAME_SIZE);
269 int main(int argc, char *argv[])
272 AVFilterGraph *graph;
273 AVFilterContext *src, *sink;
275 uint8_t errstr[1024];
277 int err, nb_frames, i;
280 fprintf(stderr, "Usage: %s <duration>\n", argv[0]);
284 duration = atof(argv[1]);
285 nb_frames = duration * INPUT_SAMPLERATE / FRAME_SIZE;
286 if (nb_frames <= 0) {
287 fprintf(stderr, "Invalid duration: %s\n", argv[1]);
291 avfilter_register_all();
293 /* Allocate the frame we will be using to store the data. */
294 frame = av_frame_alloc();
296 fprintf(stderr, "Error allocating the frame\n");
300 md5 = av_md5_alloc();
302 fprintf(stderr, "Error allocating the MD5 context\n");
306 /* Set up the filtergraph. */
307 err = init_filter_graph(&graph, &src, &sink);
309 fprintf(stderr, "Unable to init filter graph:");
313 /* the main filtering loop */
314 for (i = 0; i < nb_frames; i++) {
315 /* get an input frame to be filtered */
316 err = get_input(frame, i);
318 fprintf(stderr, "Error generating input frame:");
322 /* Send the frame to the input of the filtergraph. */
323 err = av_buffersrc_add_frame(src, frame);
325 av_frame_unref(frame);
326 fprintf(stderr, "Error submitting the frame to the filtergraph:");
330 /* Get all the filtered output that is available. */
331 while ((err = av_buffersink_get_frame(sink, frame)) >= 0) {
332 /* now do something with our filtered frame */
333 err = process_output(md5, frame);
335 fprintf(stderr, "Error processing the filtered frame:");
338 av_frame_unref(frame);
341 if (err == AVERROR(EAGAIN)) {
342 /* Need to feed more frames in. */
344 } else if (err == AVERROR_EOF) {
345 /* Nothing more to do, finish. */
347 } else if (err < 0) {
348 /* An error occurred. */
349 fprintf(stderr, "Error filtering the data:");
354 avfilter_graph_free(&graph);
355 av_frame_free(&frame);
361 av_strerror(err, errstr, sizeof(errstr));
362 fprintf(stderr, "%s\n", errstr);