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, AVChannelLayout *dst)73 static int select_channel_layout(const AVCodec *codec, AVChannelLayout *dst)
74 {
75     const AVChannelLayout *p, *best_ch_layout;
76     int best_nb_channels   = 0;
77 
78     if (!codec->ch_layouts)
79         return av_channel_layout_copy(dst, &(AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO);
80 
81     p = codec->ch_layouts;
82     while (p->nb_channels) {
83         int nb_channels = p->nb_channels;
84 
85         if (nb_channels > best_nb_channels) {
86             best_ch_layout   = p;
87             best_nb_channels = nb_channels;
88         }
89         p++;
90     }
91     return av_channel_layout_copy(dst, best_ch_layout);
92 }
93 
encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *output)94 static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt,
95                    FILE *output)
96 {
97     int ret;
98 
99     /* send the frame for encoding */
100     ret = avcodec_send_frame(ctx, frame);
101     if (ret < 0) {
102         fprintf(stderr, "Error sending the frame to the encoder\n");
103         exit(1);
104     }
105 
106     /* read all the available output packets (in general there may be any
107      * number of them */
108     while (ret >= 0) {
109         ret = avcodec_receive_packet(ctx, pkt);
110         if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
111             return;
112         else if (ret < 0) {
113             fprintf(stderr, "Error encoding audio frame\n");
114             exit(1);
115         }
116 
117         fwrite(pkt->data, 1, pkt->size, output);
118         av_packet_unref(pkt);
119     }
120 }
121 
main(int argc, char **argv)122 int main(int argc, char **argv)
123 {
124     const char *filename;
125     const AVCodec *codec;
126     AVCodecContext *c= NULL;
127     AVFrame *frame;
128     AVPacket *pkt;
129     int i, j, k, ret;
130     FILE *f;
131     uint16_t *samples;
132     float t, tincr;
133 
134     if (argc <= 1) {
135         fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
136         return 0;
137     }
138     filename = argv[1];
139 
140     /* find the MP2 encoder */
141     codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
142     if (!codec) {
143         fprintf(stderr, "Codec not found\n");
144         exit(1);
145     }
146 
147     c = avcodec_alloc_context3(codec);
148     if (!c) {
149         fprintf(stderr, "Could not allocate audio codec context\n");
150         exit(1);
151     }
152 
153     /* put sample parameters */
154     c->bit_rate = 64000;
155 
156     /* check that the encoder supports s16 pcm input */
157     c->sample_fmt = AV_SAMPLE_FMT_S16;
158     if (!check_sample_fmt(codec, c->sample_fmt)) {
159         fprintf(stderr, "Encoder does not support sample format %s",
160                 av_get_sample_fmt_name(c->sample_fmt));
161         exit(1);
162     }
163 
164     /* select other audio parameters supported by the encoder */
165     c->sample_rate    = select_sample_rate(codec);
166     ret = select_channel_layout(codec, &c->ch_layout);
167     if (ret < 0)
168         exit(1);
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     ret = av_channel_layout_copy(&frame->ch_layout, &c->ch_layout);
199     if (ret < 0)
200         exit(1);
201 
202     /* allocate the data buffers */
203     ret = av_frame_get_buffer(frame, 0);
204     if (ret < 0) {
205         fprintf(stderr, "Could not allocate audio data buffers\n");
206         exit(1);
207     }
208 
209     /* encode a single tone sound */
210     t = 0;
211     tincr = 2 * M_PI * 440.0 / c->sample_rate;
212     for (i = 0; i < 200; i++) {
213         /* make sure the frame is writable -- makes a copy if the encoder
214          * kept a reference internally */
215         ret = av_frame_make_writable(frame);
216         if (ret < 0)
217             exit(1);
218         samples = (uint16_t*)frame->data[0];
219 
220         for (j = 0; j < c->frame_size; j++) {
221             samples[2*j] = (int)(sin(t) * 10000);
222 
223             for (k = 1; k < c->ch_layout.nb_channels; k++)
224                 samples[2*j + k] = samples[2*j];
225             t += tincr;
226         }
227         encode(c, frame, pkt, f);
228     }
229 
230     /* flush the encoder */
231     encode(c, NULL, pkt, f);
232 
233     fclose(f);
234 
235     av_frame_free(&frame);
236     av_packet_free(&pkt);
237     avcodec_free_context(&c);
238 
239     return 0;
240 }
241