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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
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 
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 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 */
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 */
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) {
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 
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 
123 int main(int argc, char **argv)
124 {
125  const char *filename;
126  const AVCodec *codec;
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  /* register all the codecs */
143 
144  /* find the MP2 encoder */
146  if (!codec) {
147  fprintf(stderr, "Codec not found\n");
148  exit(1);
149  }
150 
151  c = avcodec_alloc_context3(codec);
152  if (!c) {
153  fprintf(stderr, "Could not allocate audio codec context\n");
154  exit(1);
155  }
156 
157  /* put sample parameters */
158  c->bit_rate = 64000;
159 
160  /* check that the encoder supports s16 pcm input */
162  if (!check_sample_fmt(codec, c->sample_fmt)) {
163  fprintf(stderr, "Encoder does not support sample format %s",
165  exit(1);
166  }
167 
168  /* select other audio parameters supported by the encoder */
169  c->sample_rate = select_sample_rate(codec);
172 
173  /* open it */
174  if (avcodec_open2(c, codec, NULL) < 0) {
175  fprintf(stderr, "Could not open codec\n");
176  exit(1);
177  }
178 
179  f = fopen(filename, "wb");
180  if (!f) {
181  fprintf(stderr, "Could not open %s\n", filename);
182  exit(1);
183  }
184 
185  /* packet for holding encoded output */
186  pkt = av_packet_alloc();
187  if (!pkt) {
188  fprintf(stderr, "could not allocate the packet\n");
189  exit(1);
190  }
191 
192  /* frame containing input raw audio */
193  frame = av_frame_alloc();
194  if (!frame) {
195  fprintf(stderr, "Could not allocate audio frame\n");
196  exit(1);
197  }
198 
199  frame->nb_samples = c->frame_size;
200  frame->format = c->sample_fmt;
201  frame->channel_layout = c->channel_layout;
202 
203  /* allocate the data buffers */
204  ret = av_frame_get_buffer(frame, 0);
205  if (ret < 0) {
206  fprintf(stderr, "Could not allocate audio data buffers\n");
207  exit(1);
208  }
209 
210  /* encode a single tone sound */
211  t = 0;
212  tincr = 2 * M_PI * 440.0 / c->sample_rate;
213  for (i = 0; i < 200; i++) {
214  /* make sure the frame is writable -- makes a copy if the encoder
215  * kept a reference internally */
216  ret = av_frame_make_writable(frame);
217  if (ret < 0)
218  exit(1);
219  samples = (uint16_t*)frame->data[0];
220 
221  for (j = 0; j < c->frame_size; j++) {
222  samples[2*j] = (int)(sin(t) * 10000);
223 
224  for (k = 1; k < c->channels; k++)
225  samples[2*j + k] = samples[2*j];
226  t += tincr;
227  }
228  encode(c, frame, pkt, f);
229  }
230 
231  /* flush the encoder */
232  encode(c, NULL, pkt, f);
233 
234  fclose(f);
235 
236  av_frame_free(&frame);
237  av_packet_free(&pkt);
239 
240  return 0;
241 }
#define NULL
Definition: coverity.c:32
This structure describes decoded (raw) audio or video data.
Definition: frame.h:201
AVCodec * avcodec_find_encoder(enum AVCodecID id)
Find a registered encoder with a matching codec ID.
Definition: utils.c:1232
int64_t bit_rate
the average bitrate
Definition: avcodec.h:1538
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
Read encoded data from the encoder.
Definition: encode.c:426
int size
Definition: avcodec.h:1401
static AVPacket pkt
int main(int argc, char **argv)
Definition: encode_audio.c:123
#define AV_CH_LAYOUT_STEREO
void avcodec_register_all(void)
Register all the codecs, parsers and bitstream filters which were enabled at configuration time...
Definition: allcodecs.c:664
AVCodec.
Definition: avcodec.h:3351
int av_get_channel_layout_nb_channels(uint64_t channel_layout)
Return the number of channels in the channel layout.
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:62
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2151
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:150
static AVFrame * frame
uint8_t * data
Definition: avcodec.h:1400
#define AVERROR_EOF
End of file.
Definition: error.h:55
static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
Definition: encode_audio.c:42
const uint64_t * channel_layouts
array of support channel layouts, or NULL if unknown. array is terminated by 0
Definition: avcodec.h:3375
#define AVERROR(e)
Definition: error.h:43
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:163
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:49
reference-counted frame API
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:2194
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:379
audio channel layout utility functions
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:157
AVFormatContext * ctx
Definition: movenc.c:48
static int select_channel_layout(const AVCodec *codec)
Definition: encode_audio.c:73
int format
format of the frame, -1 if unknown or unset Values correspond to enum AVPixelFormat for video frames...
Definition: frame.h:274
int frame_size
Number of samples per channel in an audio frame.
Definition: avcodec.h:2163
Libavcodec external API header.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
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:172
int sample_rate
samples per second
Definition: avcodec.h:2143
main external API structure.
Definition: avcodec.h:1488
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:590
static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *output)
Definition: encode_audio.c:95
int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame)
Supply a raw video or audio frame to the encoder.
Definition: encode.c:396
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: utils.c:614
int av_frame_get_buffer(AVFrame *frame, int align)
Allocate new buffer(s) for audio or video data.
Definition: frame.c:283
int av_frame_make_writable(AVFrame *frame)
Ensure that the frame data is writable, avoiding data copy if possible.
Definition: frame.c:566
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:215
int
common internal and external API header
signed 16 bits
Definition: samplefmt.h:61
static double c[64]
static int select_sample_rate(const AVCodec *codec)
Definition: encode_audio.c:55
int channels
number of audio channels
Definition: avcodec.h:2144
const int * supported_samplerates
array of supported audio samplerates, or NULL if unknown, array is terminated by 0 ...
Definition: avcodec.h:3373
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:51
#define M_PI
Definition: mathematics.h:52
enum AVSampleFormat * sample_fmts
array of supported sample formats, or NULL if unknown, array is terminated by -1
Definition: avcodec.h:3374
int nb_channels
This structure stores compressed data.
Definition: avcodec.h:1377
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:267
for(j=16;j >0;--j)