aboutsummaryrefslogtreecommitdiffstats
path: root/doc/examples/filtering_audio.c
blob: b28e02bfb9586a2565b7cd5b5e0fb34faed2ce24 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
/*
 * Copyright (c) 2010 Nicolas George
 * Copyright (c) 2011 Stefano Sabatini
 * Copyright (c) 2012 Clément Bœsch
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * @file
 * API example for audio decoding and filtering
 * @example doc/examples/filtering_audio.c
 */

#include <unistd.h>

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/avcodec.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>

const char *filter_descr = "aresample=8000,aconvert=s16:mono";
const char *player       = "ffplay -f s16le -ar 8000 -ac 1 -";

static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int audio_stream_index = -1;

static int open_input_file(const char *filename)
{
    int ret;
    AVCodec *dec;

    if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
        return ret;
    }

    if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
        return ret;
    }

    /* select the audio stream */
    ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot find a audio stream in the input file\n");
        return ret;
    }
    audio_stream_index = ret;
    dec_ctx = fmt_ctx->streams[audio_stream_index]->codec;

    /* init the audio decoder */
    if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
        return ret;
    }

    return 0;
}

static int init_filters(const char *filters_descr)
{
    char args[512];
    int ret;
    AVFilter *abuffersrc  = avfilter_get_by_name("abuffer");
    AVFilter *abuffersink = avfilter_get_by_name("ffabuffersink");
    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
    AVABufferSinkParams *abuffersink_params;
    const AVFilterLink *outlink;
    AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;

    filter_graph = avfilter_graph_alloc();

    /* buffer audio source: the decoded frames from the decoder will be inserted here. */
    if (!dec_ctx->channel_layout)
        dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);
    snprintf(args, sizeof(args),
            "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
             time_base.num, time_base.den, dec_ctx->sample_rate,
             av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
    ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
                                       args, NULL, filter_graph);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
        return ret;
    }

    /* buffer audio sink: to terminate the filter chain. */
    abuffersink_params = av_abuffersink_params_alloc();
    abuffersink_params->sample_fmts     = sample_fmts;
    ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
                                       NULL, abuffersink_params, filter_graph);
    av_free(abuffersink_params);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
        return ret;
    }

    /* Endpoints for the filter graph. */
    outputs->name       = av_strdup("in");
    outputs->filter_ctx = buffersrc_ctx;
    outputs->pad_idx    = 0;
    outputs->next       = NULL;

    inputs->name       = av_strdup("out");
    inputs->filter_ctx = buffersink_ctx;
    inputs->pad_idx    = 0;
    inputs->next       = NULL;

    if ((ret = avfilter_graph_parse(filter_graph, filters_descr,
                                    &inputs, &outputs, NULL)) < 0)
        return ret;

    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
        return ret;

    /* Print summary of the sink buffer
     * Note: args buffer is reused to store channel layout string */
    outlink = buffersink_ctx->inputs[0];
    av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
    av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
           (int)outlink->sample_rate,
           (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
           args);

    return 0;
}

static void print_samplesref(AVFilterBufferRef *samplesref)
{
    const AVFilterBufferRefAudioProps *props = samplesref->audio;
    const int n = props->nb_samples * av_get_channel_layout_nb_channels(props->channel_layout);
    const uint16_t *p     = (uint16_t*)samplesref->data[0];
    const uint16_t *p_end = p + n;

    while (p < p_end) {
        fputc(*p    & 0xff, stdout);
        fputc(*p>>8 & 0xff, stdout);
        p++;
    }
    fflush(stdout);
}

int main(int argc, char **argv)
{
    int ret;
    AVPacket packet;
    AVFrame frame;
    int got_frame;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
        exit(1);
    }

    avcodec_register_all();
    av_register_all();
    avfilter_register_all();

    if ((ret = open_input_file(argv[1])) < 0)
        goto end;
    if ((ret = init_filters(filter_descr)) < 0)
        goto end;

    /* read all packets */
    while (1) {
        AVFilterBufferRef *samplesref;
        if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
            break;

        if (packet.stream_index == audio_stream_index) {
            avcodec_get_frame_defaults(&frame);
            got_frame = 0;
            ret = avcodec_decode_audio4(dec_ctx, &frame, &got_frame, &packet);
            if (ret < 0) {
                av_log(NULL, AV_LOG_ERROR, "Error decoding audio\n");
                continue;
            }

            if (got_frame) {
                /* push the audio data from decoded frame into the filtergraph */
                if (av_buffersrc_add_frame(buffersrc_ctx, &frame, 0) < 0) {
                    av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
                    break;
                }

                /* pull filtered audio from the filtergraph */
                while (1) {
                    ret = av_buffersink_get_buffer_ref(buffersink_ctx, &samplesref, 0);
                    if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                        break;
                    if(ret < 0)
                        goto end;
                    if (samplesref) {
                        print_samplesref(samplesref);
                        avfilter_unref_bufferp(&samplesref);
                    }
                }
            }
        }
        av_free_packet(&packet);
    }
end:
    avfilter_graph_free(&filter_graph);
    if (dec_ctx)
        avcodec_close(dec_ctx);
    avformat_close_input(&fmt_ctx);

    if (ret < 0 && ret != AVERROR_EOF) {
        char buf[1024];
        av_strerror(ret, buf, sizeof(buf));
        fprintf(stderr, "Error occurred: %s\n", buf);
        exit(1);
    }

    exit(0);
}