FFmpeg 5.1.6
decode_audio.c
Go to the documentation of this file.
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
42static 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->ch_layout.nb_channels; ch++)
101 fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
102 }
103}
104
105int 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
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->ch_layout.nb_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);
226end:
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.
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.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
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:427
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: defs.h:40
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.
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.
AVCodecParserContext * av_parser_init(int codec_id)
#define AVERROR_EOF
End of file.
Definition: error.h:57
#define AVERROR(e)
Definition: error.h:45
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.
enum AVSampleFormat av_get_packed_sample_fmt(enum AVSampleFormat sample_fmt)
Get the packed alternative form of the given sample format.
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.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:55
@ AV_SAMPLE_FMT_FLT
float
Definition: samplefmt.h:60
@ AV_SAMPLE_FMT_S32
signed 32 bits
Definition: samplefmt.h:59
@ AV_SAMPLE_FMT_U8
unsigned 8 bits
Definition: samplefmt.h:57
@ AV_SAMPLE_FMT_DBL
double
Definition: samplefmt.h:61
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:58
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
#define AV_NE(be, le)
Definition: macros.h:33
#define FF_ARRAY_ELEMS(a)
Definition: macros.h:53
Memory handling functions.
int nb_channels
Number of channels in this layout.
main external API structure.
Definition: avcodec.h:389
AVChannelLayout ch_layout
Audio channel layout.
Definition: avcodec.h:2056
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:1014
int sample_rate
samples per second
Definition: avcodec.h:998
AVCodec.
Definition: codec.h:196
enum AVCodecID id
Definition: codec.h:210
This structure describes decoded (raw) audio or video data.
Definition: frame.h:325
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:405
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:346
This structure stores compressed data.
Definition: packet.h:351
int size
Definition: packet.h:375
uint8_t * data
Definition: packet.h:374