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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 int main(int argc, char **argv)
43 {
44  const char *outfilename, *filename;
45  const AVCodec *codec;
46  AVCodecContext *c= NULL;
47  int len;
48  FILE *f, *outfile;
50  AVPacket avpkt;
51  AVFrame *decoded_frame = NULL;
52 
53  if (argc <= 2) {
54  fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
55  exit(0);
56  }
57  filename = argv[1];
58  outfilename = argv[2];
59 
60  /* register all the codecs */
62 
63  av_init_packet(&avpkt);
64 
65  /* find the MPEG audio decoder */
67  if (!codec) {
68  fprintf(stderr, "Codec not found\n");
69  exit(1);
70  }
71 
72  c = avcodec_alloc_context3(codec);
73  if (!c) {
74  fprintf(stderr, "Could not allocate audio codec context\n");
75  exit(1);
76  }
77 
78  /* open it */
79  if (avcodec_open2(c, codec, NULL) < 0) {
80  fprintf(stderr, "Could not open codec\n");
81  exit(1);
82  }
83 
84  f = fopen(filename, "rb");
85  if (!f) {
86  fprintf(stderr, "Could not open %s\n", filename);
87  exit(1);
88  }
89  outfile = fopen(outfilename, "wb");
90  if (!outfile) {
91  av_free(c);
92  exit(1);
93  }
94 
95  /* decode until eof */
96  avpkt.data = inbuf;
97  avpkt.size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
98 
99  while (avpkt.size > 0) {
100  int i, ch;
101  int got_frame = 0;
102 
103  if (!decoded_frame) {
104  if (!(decoded_frame = av_frame_alloc())) {
105  fprintf(stderr, "Could not allocate audio frame\n");
106  exit(1);
107  }
108  }
109 
110  len = avcodec_decode_audio4(c, decoded_frame, &got_frame, &avpkt);
111  if (len < 0) {
112  fprintf(stderr, "Error while decoding\n");
113  exit(1);
114  }
115  if (got_frame) {
116  /* if a frame has been decoded, output it */
117  int data_size = av_get_bytes_per_sample(c->sample_fmt);
118  if (data_size < 0) {
119  /* This should not occur, checking just for paranoia */
120  fprintf(stderr, "Failed to calculate data size\n");
121  exit(1);
122  }
123  for (i=0; i<decoded_frame->nb_samples; i++)
124  for (ch=0; ch<c->channels; ch++)
125  fwrite(decoded_frame->data[ch] + data_size*i, 1, data_size, outfile);
126  }
127  avpkt.size -= len;
128  avpkt.data += len;
129  avpkt.dts =
130  avpkt.pts = AV_NOPTS_VALUE;
131  if (avpkt.size < AUDIO_REFILL_THRESH) {
132  /* Refill the input buffer, to avoid trying to decode
133  * incomplete frames. Instead of this, one could also use
134  * a parser, or use a proper container format through
135  * libavformat. */
136  memmove(inbuf, avpkt.data, avpkt.size);
137  avpkt.data = inbuf;
138  len = fread(avpkt.data + avpkt.size, 1,
139  AUDIO_INBUF_SIZE - avpkt.size, f);
140  if (len > 0)
141  avpkt.size += len;
142  }
143  }
144 
145  fclose(outfile);
146  fclose(f);
147 
149  av_frame_free(&decoded_frame);
150 
151  return 0;
152 }
This structure describes decoded (raw) audio or video data.
Definition: frame.h:187
Memory handling functions.
int size
Definition: avcodec.h:1658
attribute_deprecated int avcodec_decode_audio4(AVCodecContext *avctx, AVFrame *frame, int *got_frame_ptr, const AVPacket *avpkt)
Decode the audio frame of size avpkt->size from avpkt->data into frame.
void avcodec_register_all(void)
Register all the codecs, parsers and bitstream filters which were enabled at configuration time...
AVCodec.
Definition: avcodec.h:3681
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2502
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
#define AUDIO_REFILL_THRESH
Definition: decode_audio.c:40
uint8_t * data
Definition: avcodec.h:1657
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
reference-counted frame API
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Libavcodec external API header.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer...
main external API structure.
Definition: avcodec.h:1732
AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
#define AUDIO_INBUF_SIZE
Definition: decode_audio.c:39
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
void av_free(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family...
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:201
int av_get_bytes_per_sample(enum AVSampleFormat sample_fmt)
Return number of bytes per sample.
void av_init_packet(AVPacket *pkt)
Initialize optional fields of a packet with default values.
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:769
int channels
number of audio channels
Definition: avcodec.h:2495
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed...
Definition: avcodec.h:1656
int main(int argc, char **argv)
Definition: decode_audio.c:42
This structure stores compressed data.
Definition: avcodec.h:1634
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:244
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1650
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248