FFmpeg  4.3.1
decode_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 decoding with libavcodec API example
26  *
27  * @example decode_audio.c
28  */
29 
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 
34 #include <libavutil/frame.h>
35 #include <libavutil/mem.h>
36 
37 #include <libavcodec/avcodec.h>
38 
39 #define AUDIO_INBUF_SIZE 20480
40 #define AUDIO_REFILL_THRESH 4096
41 
42 static int get_format_from_sample_fmt(const char **fmt,
43  enum AVSampleFormat sample_fmt)
44 {
45  int i;
46  struct sample_fmt_entry {
47  enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
48  } sample_fmt_entries[] = {
49  { AV_SAMPLE_FMT_U8, "u8", "u8" },
50  { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
51  { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
52  { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
53  { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
54  };
55  *fmt = NULL;
56 
57  for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
58  struct sample_fmt_entry *entry = &sample_fmt_entries[i];
59  if (sample_fmt == entry->sample_fmt) {
60  *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
61  return 0;
62  }
63  }
64 
65  fprintf(stderr,
66  "sample format %s is not supported as output format\n",
67  av_get_sample_fmt_name(sample_fmt));
68  return -1;
69 }
70 
72  FILE *outfile)
73 {
74  int i, ch;
75  int ret, data_size;
76 
77  /* send the packet with the compressed data to the decoder */
79  if (ret < 0) {
80  fprintf(stderr, "Error submitting the packet to the decoder\n");
81  exit(1);
82  }
83 
84  /* read all the output frames (in general there may be any number of them */
85  while (ret >= 0) {
87  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
88  return;
89  else if (ret < 0) {
90  fprintf(stderr, "Error during decoding\n");
91  exit(1);
92  }
94  if (data_size < 0) {
95  /* This should not occur, checking just for paranoia */
96  fprintf(stderr, "Failed to calculate data size\n");
97  exit(1);
98  }
99  for (i = 0; i < frame->nb_samples; i++)
100  for (ch = 0; ch < dec_ctx->channels; ch++)
101  fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
102  }
103 }
104 
105 int main(int argc, char **argv)
106 {
107  const char *outfilename, *filename;
108  const AVCodec *codec;
109  AVCodecContext *c= NULL;
110  AVCodecParserContext *parser = NULL;
111  int len, ret;
112  FILE *f, *outfile;
114  uint8_t *data;
115  size_t data_size;
116  AVPacket *pkt;
117  AVFrame *decoded_frame = NULL;
118  enum AVSampleFormat sfmt;
119  int n_channels = 0;
120  const char *fmt;
121 
122  if (argc <= 2) {
123  fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
124  exit(0);
125  }
126  filename = argv[1];
127  outfilename = argv[2];
128 
129  pkt = av_packet_alloc();
130 
131  /* find the MPEG audio decoder */
133  if (!codec) {
134  fprintf(stderr, "Codec not found\n");
135  exit(1);
136  }
137 
138  parser = av_parser_init(codec->id);
139  if (!parser) {
140  fprintf(stderr, "Parser not found\n");
141  exit(1);
142  }
143 
144  c = avcodec_alloc_context3(codec);
145  if (!c) {
146  fprintf(stderr, "Could not allocate audio codec context\n");
147  exit(1);
148  }
149 
150  /* open it */
151  if (avcodec_open2(c, codec, NULL) < 0) {
152  fprintf(stderr, "Could not open codec\n");
153  exit(1);
154  }
155 
156  f = fopen(filename, "rb");
157  if (!f) {
158  fprintf(stderr, "Could not open %s\n", filename);
159  exit(1);
160  }
161  outfile = fopen(outfilename, "wb");
162  if (!outfile) {
163  av_free(c);
164  exit(1);
165  }
166 
167  /* decode until eof */
168  data = inbuf;
169  data_size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
170 
171  while (data_size > 0) {
172  if (!decoded_frame) {
173  if (!(decoded_frame = av_frame_alloc())) {
174  fprintf(stderr, "Could not allocate audio frame\n");
175  exit(1);
176  }
177  }
178 
179  ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
180  data, data_size,
182  if (ret < 0) {
183  fprintf(stderr, "Error while parsing\n");
184  exit(1);
185  }
186  data += ret;
187  data_size -= ret;
188 
189  if (pkt->size)
190  decode(c, pkt, decoded_frame, outfile);
191 
192  if (data_size < AUDIO_REFILL_THRESH) {
193  memmove(inbuf, data, data_size);
194  data = inbuf;
195  len = fread(data + data_size, 1,
196  AUDIO_INBUF_SIZE - data_size, f);
197  if (len > 0)
198  data_size += len;
199  }
200  }
201 
202  /* flush the decoder */
203  pkt->data = NULL;
204  pkt->size = 0;
205  decode(c, pkt, decoded_frame, outfile);
206 
207  /* print output pcm infomations, because there have no metadata of pcm */
208  sfmt = c->sample_fmt;
209 
210  if (av_sample_fmt_is_planar(sfmt)) {
211  const char *packed = av_get_sample_fmt_name(sfmt);
212  printf("Warning: the sample format the decoder produced is planar "
213  "(%s). This example will output the first channel only.\n",
214  packed ? packed : "?");
215  sfmt = av_get_packed_sample_fmt(sfmt);
216  }
217 
218  n_channels = c->channels;
219  if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
220  goto end;
221 
222  printf("Play the output audio file with the command:\n"
223  "ffplay -f %s -ac %d -ar %d %s\n",
224  fmt, n_channels, c->sample_rate,
225  outfilename);
226 end:
227  fclose(outfile);
228  fclose(f);
229 
231  av_parser_close(parser);
232  av_frame_free(&decoded_frame);
234 
235  return 0;
236 }
Libavcodec external API header.
#define AV_NE(be, le)
Definition: common.h:50
#define FF_ARRAY_ELEMS(a)
Definition: common.h:100
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
Definition: decode_audio.c:71
#define AUDIO_INBUF_SIZE
Definition: decode_audio.c:39
int main(int argc, char **argv)
Definition: decode_audio.c:105
static int get_format_from_sample_fmt(const char **fmt, enum AVSampleFormat sample_fmt)
Definition: decode_audio.c:42
#define AUDIO_REFILL_THRESH
Definition: decode_audio.c:40
static AVPacket pkt
static AVFrame * frame
static AVCodecContext * dec_ctx
reference-counted frame API
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
@ AV_CODEC_ID_MP2
Definition: codec_id.h:410
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding.
Definition: avcodec.h:215
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
AVCodecParserContext * av_parser_init(int codec_id)
void av_parser_close(AVCodecParserContext *s)
int av_parser_parse2(AVCodecParserContext *s, AVCodecContext *avctx, uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size, int64_t pts, int64_t dts, int64_t pos)
Parse a packet.
#define AVERROR_EOF
End of file.
Definition: error.h:55
#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.
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
void av_free(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family.
int av_sample_fmt_is_planar(enum AVSampleFormat sample_fmt)
Check if the sample format is planar.
int av_get_bytes_per_sample(enum AVSampleFormat sample_fmt)
Return number of bytes per sample.
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.
enum AVSampleFormat av_get_packed_sample_fmt(enum AVSampleFormat sample_fmt)
Get the packed alternative form of the given sample format.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
@ AV_SAMPLE_FMT_FLT
float
Definition: samplefmt.h:63
@ AV_SAMPLE_FMT_S32
signed 32 bits
Definition: samplefmt.h:62
@ AV_SAMPLE_FMT_U8
unsigned 8 bits
Definition: samplefmt.h:60
@ AV_SAMPLE_FMT_DBL
double
Definition: samplefmt.h:64
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:61
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
Memory handling functions.
main external API structure.
Definition: avcodec.h:526
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:1194
int sample_rate
samples per second
Definition: avcodec.h:1186
int channels
number of audio channels
Definition: avcodec.h:1187
AVCodec.
Definition: codec.h:190
enum AVCodecID id
Definition: codec.h:204
This structure describes decoded (raw) audio or video data.
Definition: frame.h:300
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:366
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:314
This structure stores compressed data.
Definition: packet.h:332
int size
Definition: packet.h:356
uint8_t * data
Definition: packet.h:355