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)
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  /* find the MP2 encoder */
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 */
159  if (!check_sample_fmt(codec, c->sample_fmt)) {
160  fprintf(stderr, "Encoder does not support sample format %s",
162  exit(1);
163  }
164 
165  /* select other audio parameters supported by the encoder */
166  c->sample_rate = select_sample_rate(codec);
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);
236 
237  return 0;
238 }
#define NULL
Definition: coverity.c:32
This structure describes decoded (raw) audio or video data.
Definition: frame.h:295
AVCodec * avcodec_find_encoder(enum AVCodecID id)
Find a registered encoder with a matching codec ID.
Definition: allcodecs.c:891
int64_t bit_rate
the average bitrate
Definition: avcodec.h:1618
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
Read encoded data from the encoder.
Definition: encode.c:423
int size
Definition: avcodec.h:1481
static AVPacket pkt
int main(int argc, char **argv)
Definition: encode_audio.c:123
#define AV_CH_LAYOUT_STEREO
AVCodec.
Definition: avcodec.h:3492
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:2236
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:189
#define f(width, name)
Definition: cbs_vp9.c:255
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
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
uint8_t * data
Definition: avcodec.h:1480
#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:3516
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:202
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:2279
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:472
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:156
AVFormatContext * ctx
Definition: movenc.c:48
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
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:368
int frame_size
Number of samples per channel in an audio frame.
Definition: avcodec.h:2248
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:171
int sample_rate
samples per second
Definition: avcodec.h:2228
#define abs(x)
Definition: cuda_runtime.h:35
main external API structure.
Definition: avcodec.h:1568
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:599
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:393
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: utils.c:548
int av_frame_get_buffer(AVFrame *frame, int align)
Allocate new buffer(s) for audio or video data.
Definition: frame.c:324
int av_frame_make_writable(AVFrame *frame)
Ensure that the frame data is writable, avoiding data copy if possible.
Definition: frame.c:611
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:309
int
common internal and external API header
signed 16 bits
Definition: samplefmt.h:61
static int select_sample_rate(const AVCodec *codec)
Definition: encode_audio.c:55
int channels
number of audio channels
Definition: avcodec.h:2229
const int * supported_samplerates
array of supported audio samplerates, or NULL if unknown, array is terminated by 0 ...
Definition: avcodec.h:3514
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:51
Filter the word “frame” indicates either a video frame or a group of audio samples
#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:3515
int nb_channels
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
This structure stores compressed data.
Definition: avcodec.h:1457
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:361
for(j=16;j >0;--j)