1 /*
2 * Copyright (c) 2001 Fabrice Bellard
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to deal
6 * in the Software without restriction, including without limitation the rights
7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 * copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
17 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 * THE SOFTWARE.
21 */
22
23 /**
24 * @file
25 * audio encoding with libavcodec API example.
26 *
27 * @example encode_audio.c
28 */
29
30 #include <stdint.h>
31 #include <stdio.h>
32 #include <stdlib.h>
33
34 #include <libavcodec/avcodec.h>
35
36 #include <libavutil/channel_layout.h>
37 #include <libavutil/common.h>
38 #include <libavutil/frame.h>
39 #include <libavutil/samplefmt.h>
40
41 /* check that a given sample format is supported by the encoder */
check_sample_fmt(const AVCodec * codec,enum AVSampleFormat sample_fmt)42 static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
43 {
44 const enum AVSampleFormat *p = codec->sample_fmts;
45
46 while (*p != AV_SAMPLE_FMT_NONE) {
47 if (*p == sample_fmt)
48 return 1;
49 p++;
50 }
51 return 0;
52 }
53
54 /* just pick the highest supported samplerate */
select_sample_rate(const AVCodec * codec)55 static int select_sample_rate(const AVCodec *codec)
56 {
57 const int *p;
58 int best_samplerate = 0;
59
60 if (!codec->supported_samplerates)
61 return 44100;
62
63 p = codec->supported_samplerates;
64 while (*p) {
65 if (!best_samplerate || abs(44100 - *p) < abs(44100 - best_samplerate))
66 best_samplerate = *p;
67 p++;
68 }
69 return best_samplerate;
70 }
71
72 /* select layout with the highest channel count */
select_channel_layout(const AVCodec * codec)73 static int select_channel_layout(const AVCodec *codec)
74 {
75 const uint64_t *p;
76 uint64_t best_ch_layout = 0;
77 int best_nb_channels = 0;
78
79 if (!codec->channel_layouts)
80 return AV_CH_LAYOUT_STEREO;
81
82 p = codec->channel_layouts;
83 while (*p) {
84 int nb_channels = av_get_channel_layout_nb_channels(*p);
85
86 if (nb_channels > best_nb_channels) {
87 best_ch_layout = *p;
88 best_nb_channels = nb_channels;
89 }
90 p++;
91 }
92 return best_ch_layout;
93 }
94
encode(AVCodecContext * ctx,AVFrame * frame,AVPacket * pkt,FILE * output)95 static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt,
96 FILE *output)
97 {
98 int ret;
99
100 /* send the frame for encoding */
101 ret = avcodec_send_frame(ctx, frame);
102 if (ret < 0) {
103 fprintf(stderr, "Error sending the frame to the encoder\n");
104 exit(1);
105 }
106
107 /* read all the available output packets (in general there may be any
108 * number of them */
109 while (ret >= 0) {
110 ret = avcodec_receive_packet(ctx, pkt);
111 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
112 return;
113 else if (ret < 0) {
114 fprintf(stderr, "Error encoding audio frame\n");
115 exit(1);
116 }
117
118 fwrite(pkt->data, 1, pkt->size, output);
119 av_packet_unref(pkt);
120 }
121 }
122
main(int argc,char ** argv)123 int main(int argc, char **argv)
124 {
125 const char *filename;
126 const AVCodec *codec;
127 AVCodecContext *c= NULL;
128 AVFrame *frame;
129 AVPacket *pkt;
130 int i, j, k, ret;
131 FILE *f;
132 uint16_t *samples;
133 float t, tincr;
134
135 if (argc <= 1) {
136 fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
137 return 0;
138 }
139 filename = argv[1];
140
141 /* find the MP2 encoder */
142 codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
143 if (!codec) {
144 fprintf(stderr, "Codec not found\n");
145 exit(1);
146 }
147
148 c = avcodec_alloc_context3(codec);
149 if (!c) {
150 fprintf(stderr, "Could not allocate audio codec context\n");
151 exit(1);
152 }
153
154 /* put sample parameters */
155 c->bit_rate = 64000;
156
157 /* check that the encoder supports s16 pcm input */
158 c->sample_fmt = AV_SAMPLE_FMT_S16;
159 if (!check_sample_fmt(codec, c->sample_fmt)) {
160 fprintf(stderr, "Encoder does not support sample format %s",
161 av_get_sample_fmt_name(c->sample_fmt));
162 exit(1);
163 }
164
165 /* select other audio parameters supported by the encoder */
166 c->sample_rate = select_sample_rate(codec);
167 c->channel_layout = select_channel_layout(codec);
168 c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
169
170 /* open it */
171 if (avcodec_open2(c, codec, NULL) < 0) {
172 fprintf(stderr, "Could not open codec\n");
173 exit(1);
174 }
175
176 f = fopen(filename, "wb");
177 if (!f) {
178 fprintf(stderr, "Could not open %s\n", filename);
179 exit(1);
180 }
181
182 /* packet for holding encoded output */
183 pkt = av_packet_alloc();
184 if (!pkt) {
185 fprintf(stderr, "could not allocate the packet\n");
186 exit(1);
187 }
188
189 /* frame containing input raw audio */
190 frame = av_frame_alloc();
191 if (!frame) {
192 fprintf(stderr, "Could not allocate audio frame\n");
193 exit(1);
194 }
195
196 frame->nb_samples = c->frame_size;
197 frame->format = c->sample_fmt;
198 frame->channel_layout = c->channel_layout;
199
200 /* allocate the data buffers */
201 ret = av_frame_get_buffer(frame, 0);
202 if (ret < 0) {
203 fprintf(stderr, "Could not allocate audio data buffers\n");
204 exit(1);
205 }
206
207 /* encode a single tone sound */
208 t = 0;
209 tincr = 2 * M_PI * 440.0 / c->sample_rate;
210 for (i = 0; i < 200; i++) {
211 /* make sure the frame is writable -- makes a copy if the encoder
212 * kept a reference internally */
213 ret = av_frame_make_writable(frame);
214 if (ret < 0)
215 exit(1);
216 samples = (uint16_t*)frame->data[0];
217
218 for (j = 0; j < c->frame_size; j++) {
219 samples[2*j] = (int)(sin(t) * 10000);
220
221 for (k = 1; k < c->channels; k++)
222 samples[2*j + k] = samples[2*j];
223 t += tincr;
224 }
225 encode(c, frame, pkt, f);
226 }
227
228 /* flush the encoder */
229 encode(c, NULL, pkt, f);
230
231 fclose(f);
232
233 av_frame_free(&frame);
234 av_packet_free(&pkt);
235 avcodec_free_context(&c);
236
237 return 0;
238 }
239