FFmpeg
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, AVChannelLayout *dst)
74 {
75  const AVChannelLayout *p, *best_ch_layout;
76  int best_nb_channels = 0;
77 
78  if (!codec->ch_layouts)
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 
95  FILE *output)
96 {
97  int ret;
98 
99  /* send the frame for encoding */
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) {
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);
119  }
120 }
121 
122 int main(int argc, char **argv)
123 {
124  const char *filename;
125  const AVCodec *codec;
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 */
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 */
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 */
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 
238 
239  return 0;
240 }
AVCodec::ch_layouts
const AVChannelLayout * ch_layouts
Array of supported channel layouts, terminated with a zeroed layout.
Definition: codec.h:246
main
int main(int argc, char **argv)
Definition: encode_audio.c:122
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:422
AVCodec
AVCodec.
Definition: codec.h:196
avcodec_receive_packet
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
Read encoded data from the encoder.
Definition: encode.c:391
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
av_frame_get_buffer
int av_frame_get_buffer(AVFrame *frame, int align)
Allocate new buffer(s) for audio or video data.
Definition: frame.c:254
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:57
output
filter_frame For filters that do not use the this method is called when a frame is pushed to the filter s input It can be called at any time except in a reentrant way If the input frame is enough to produce output
Definition: filter_design.txt:225
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:111
avcodec_find_encoder
const AVCodec * avcodec_find_encoder(enum AVCodecID id)
Find a registered encoder with a matching codec ID.
Definition: allcodecs.c:928
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:325
av_frame_make_writable
int av_frame_make_writable(AVFrame *frame)
Ensure that the frame data is writable, avoiding data copy if possible.
Definition: frame.c:540
AVPacket::data
uint8_t * data
Definition: packet.h:374
AV_CHANNEL_LAYOUT_STEREO
#define AV_CHANNEL_LAYOUT_STEREO
Definition: channel_layout.h:354
AVChannelLayout::nb_channels
int nb_channels
Number of channels in this layout.
Definition: channel_layout.h:300
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:73
av_channel_layout_copy
int av_channel_layout_copy(AVChannelLayout *dst, const AVChannelLayout *src)
Make a copy of a channel layout.
Definition: channel_layout.c:637
AVCodec::sample_fmts
enum AVSampleFormat * sample_fmts
array of supported sample formats, or NULL if unknown, array is terminated by -1
Definition: codec.h:220
samplefmt.h
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:99
AVCodec::supported_samplerates
const int * supported_samplerates
array of supported audio samplerates, or NULL if unknown, array is terminated by 0
Definition: codec.h:219
pkt
AVPacket * pkt
Definition: movenc.c:59
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:149
AV_CODEC_ID_MP2
@ AV_CODEC_ID_MP2
Definition: codec_id.h:426
check_sample_fmt
static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
Definition: encode_audio.c:42
ctx
AVFormatContext * ctx
Definition: movenc.c:48
av_get_sample_fmt_name
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:51
NULL
#define NULL
Definition: coverity.c:32
avcodec_free_context
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
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: avcodec.c:115
abs
#define abs(x)
Definition: cuda_runtime.h:35
select_channel_layout
static int select_channel_layout(const AVCodec *codec, AVChannelLayout *dst)
Definition: encode_audio.c:73
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
f
f
Definition: af_crystalizer.c:122
AVPacket::size
int size
Definition: packet.h:375
AVChannelLayout
An AVChannelLayout holds information about the channel layout of audio data.
Definition: channel_layout.h:290
for
for(k=2;k<=8;++k)
Definition: h264pred_template.c:425
AV_SAMPLE_FMT_NONE
@ AV_SAMPLE_FMT_NONE
Definition: samplefmt.h:56
frame.h
encode
static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *output)
Definition: encode_audio.c:94
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:62
M_PI
#define M_PI
Definition: mathematics.h:52
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:271
common.h
AVSampleFormat
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:55
AV_SAMPLE_FMT_S16
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:58
select_sample_rate
static int select_sample_rate(const AVCodec *codec)
Definition: encode_audio.c:55
avcodec_send_frame
int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame)
Supply a raw video or audio frame to the encoder.
Definition: encode.c:358
avcodec.h
ret
ret
Definition: filter_design.txt:187
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
AVCodecContext
main external API structure.
Definition: avcodec.h:389
channel_layout.h
samples
Filter the word “frame” indicates either a video frame or a group of audio samples
Definition: filter_design.txt:8
AVPacket
This structure stores compressed data.
Definition: packet.h:351
int
int
Definition: ffmpeg_filter.c:153