FFmpeg: doc/examples/encode_audio.c Source File

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encode_audio.c
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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 libavcodec encoding audio API usage examples
25 * @example encode_audio.c
26 *
27 * Generate a synthetic audio signal and encode it to an output MP2 file.
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 */
42 static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
43{
44 const void *out_config;
46 0, &out_config, NULL);
47 if (ret < 0) {
48 fprintf(stderr, "Error getting supported sample formats\n");
49 exit(1);
50 }
51 const enum AVSampleFormat *p = out_config;
52
53 if (!p)
54 return 1;
55
56 while (*p != AV_SAMPLE_FMT_NONE) {
57 if (*p == sample_fmt)
58 return 1;
59 p++;
60 }
61 return 0;
62}
63
64/* just pick the highest supported samplerate */
65 static int select_sample_rate(const AVCodec *codec)
66{
67 const void *out_config;
69 0, &out_config, NULL);
70 if (ret < 0) {
71 fprintf(stderr, "Error getting supported sample rates\n");
72 exit(1);
73 }
74 const int *p = out_config;
75 int best_samplerate = 0;
76
77 if (!p)
78 return 44100;
79
80 while (*p) {
81 if (!best_samplerate || abs(44100 - *p) < abs(44100 - best_samplerate))
82 best_samplerate = *p;
83 p++;
84 }
85 return best_samplerate;
86}
87
88/* select layout with the highest channel count */
90{
91 const void *out_config;
93 0, &out_config, NULL);
94 if (ret < 0) {
95 fprintf(stderr, "Error getting supported channel layouts\n");
96 exit(1);
97 }
98 const AVChannelLayout *p = out_config, *best_ch_layout;
99 int best_nb_channels = 0;
100
101 if (!p)
103
104 while (p->nb_channels) {
105 int nb_channels = p->nb_channels;
106
107 if (nb_channels > best_nb_channels) {
108 best_ch_layout = p;
109 best_nb_channels = nb_channels;
110 }
111 p++;
112 }
113 return av_channel_layout_copy(dst, best_ch_layout);
114}
115
117 FILE *output)
118{
119 int ret;
120
121 /* send the frame for encoding */
123 if (ret < 0) {
124 fprintf(stderr, "Error sending the frame to the encoder\n");
125 exit(1);
126 }
127
128 /* read all the available output packets (in general there may be any
129 * number of them */
130 while (ret >= 0) {
132 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
133 return;
134 else if (ret < 0) {
135 fprintf(stderr, "Error encoding audio frame\n");
136 exit(1);
137 }
138
139 fwrite(pkt->data, 1, pkt->size, output);
141 }
142}
143
144 int main(int argc, char **argv)
145{
146 const char *filename;
147 const AVCodec *codec;
149 AVFrame *frame;
150 AVPacket *pkt;
151 int i, j, k, ret;
152 FILE *f;
153 uint16_t *samples;
154 float t, tincr;
155
156 if (argc <= 1) {
157 fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
158 return 0;
159 }
160 filename = argv[1];
161
162 /* find the MP2 encoder */
164 if (!codec) {
165 fprintf(stderr, "Codec not found\n");
166 exit(1);
167 }
168
169 c = avcodec_alloc_context3(codec);
170 if (!c) {
171 fprintf(stderr, "Could not allocate audio codec context\n");
172 exit(1);
173 }
174
175 /* put sample parameters */
176 c->bit_rate = 64000;
177
178 /* check that the encoder supports s16 pcm input */
179 c->sample_fmt = AV_SAMPLE_FMT_S16;
180 if (!check_sample_fmt(codec, c->sample_fmt)) {
181 fprintf(stderr, "Encoder does not support sample format %s",
182 av_get_sample_fmt_name(c->sample_fmt));
183 exit(1);
184 }
185
186 /* select other audio parameters supported by the encoder */
187 c->sample_rate = select_sample_rate(codec);
188 ret = select_channel_layout(codec, &c->ch_layout);
189 if (ret < 0)
190 exit(1);
191
192 /* open it */
193 if (avcodec_open2(c, codec, NULL) < 0) {
194 fprintf(stderr, "Could not open codec\n");
195 exit(1);
196 }
197
198 f = fopen(filename, "wb");
199 if (!f) {
200 fprintf(stderr, "Could not open %s\n", filename);
201 exit(1);
202 }
203
204 /* packet for holding encoded output */
206 if (!pkt) {
207 fprintf(stderr, "could not allocate the packet\n");
208 exit(1);
209 }
210
211 /* frame containing input raw audio */
213 if (!frame) {
214 fprintf(stderr, "Could not allocate audio frame\n");
215 exit(1);
216 }
217
218 frame->nb_samples = c->frame_size;
219 frame->format = c->sample_fmt;
220 ret = av_channel_layout_copy(&frame->ch_layout, &c->ch_layout);
221 if (ret < 0)
222 exit(1);
223
224 /* allocate the data buffers */
225 ret = av_frame_get_buffer(frame, 0);
226 if (ret < 0) {
227 fprintf(stderr, "Could not allocate audio data buffers\n");
228 exit(1);
229 }
230
231 /* encode a single tone sound */
232 t = 0;
233 tincr = 2 * M_PI * 440.0 / c->sample_rate;
234 for (i = 0; i < 200; i++) {
235 /* make sure the frame is writable -- makes a copy if the encoder
236 * kept a reference internally */
238 if (ret < 0)
239 exit(1);
240 samples = (uint16_t*)frame->data[0];
241
242 for (j = 0; j < c->frame_size; j++) {
243 samples[c->ch_layout.nb_channels*j] = (int)(sin(t) * 10000);
244
245 for (k = 1; k < c->ch_layout.nb_channels; k++)
246 samples[c->ch_layout.nb_channels*j + k] = samples[c->ch_layout.nb_channels*j];
247 t += tincr;
248 }
249 encode(c, frame, pkt, f);
250 }
251
252 /* flush the encoder */
253 encode(c, NULL, pkt, f);
254
255 fclose(f);
256
260
261 return 0;
262}
uint8_t ptrdiff_t const uint8_t ptrdiff_t int intptr_t intptr_t int int16_t * dst
Definition dsp.h:87
static AVFormatContext * ctx
Libavcodec external API header.
i
#define i(width, name, range_min, range_max)
Definition cbs_h264.c:63
f
#define f(width, name)
Definition cbs_vp8.c:236
Public libavutil channel layout APIs header.
common internal and external API header
#define NULL
Definition coverity.c:32
#define abs(x)
Definition cuda_runtime.h:35
static AVPacket * pkt
Definition demux_decode.c:55
static AVFrame * frame
Definition demux_decode.c:54
int main
Definition dovi_rpuenc.c:38
static int select_channel_layout(const AVCodec *codec, AVChannelLayout *dst)
Definition encode_audio.c:89
static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *output)
Definition encode_audio.c:116
static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
Definition encode_audio.c:42
static int select_sample_rate(const AVCodec *codec)
Definition encode_audio.c:65
reference-counted frame API
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition avcodec.c:144
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition options.c:149
const AVCodec * avcodec_find_encoder(enum AVCodecID id)
Find a registered encoder with a matching codec ID.
Definition allcodecs.c:986
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
Definition options.c:164
@ AV_CODEC_ID_MP2
Definition codec_id.h:453
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
Read encoded data from the encoder.
Definition encode.c:578
int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame)
Supply a raw video or audio frame to the encoder.
Definition encode.c:545
int avcodec_get_supported_config(const AVCodecContext *avctx, const AVCodec *codec, enum AVCodecConfig config, unsigned flags, const void **out, int *out_num)
Retrieve a list of all supported values for a given configuration type.
Definition avcodec.c:818
@ AV_CODEC_CONFIG_SAMPLE_FORMAT
AVSampleFormat, terminated by AV_SAMPLE_FMT_NONE.
Definition avcodec.h:2587
@ AV_CODEC_CONFIG_SAMPLE_RATE
int, terminated by 0
Definition avcodec.h:2586
@ AV_CODEC_CONFIG_CHANNEL_LAYOUT
AVChannelLayout, terminated by {0}.
Definition avcodec.h:2588
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition packet.c:74
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition packet.c:434
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition packet.c:63
#define AV_CHANNEL_LAYOUT_STEREO
int av_channel_layout_copy(AVChannelLayout *dst, const AVChannelLayout *src)
Make a copy of a channel layout.
#define AVERROR_EOF
End of file.
Definition error.h:57
#define AVERROR(e)
Definition error.h:45
int av_frame_get_buffer(AVFrame *frame, int align)
Allocate new buffer(s) for audio or video data.
Definition frame.c:206
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition frame.c:64
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition frame.c:52
int av_frame_make_writable(AVFrame *frame)
Ensure that the frame data is writable, avoiding data copy if possible.
Definition frame.c:552
const char * av_get_sample_fmt_name(enum AVSampleFormat sample_fmt)
Return the name of sample_fmt, or NULL if sample_fmt is not recognized.
Definition samplefmt.c:52
AVSampleFormat
Audio sample formats.
Definition samplefmt.h:55
@ AV_SAMPLE_FMT_NONE
Definition samplefmt.h:56
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition samplefmt.h:58
#define M_PI
Definition mathematics.h:67
An AVChannelLayout holds information about the channel layout of audio data.
main external API structure.
Definition avcodec.h:443
AVCodec.
Definition codec.h:175
This structure describes decoded (raw) audio or video data.
Definition frame.h:472
This structure stores compressed data.
Definition packet.h:580
c
static double c[64]
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