FFmpeg 7.1.1
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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 libavcodec audio decoding API usage example
25 * @example decode_audio.c
26 *
27 * Decode data from an MP2 input file and generate a raw audio file to
28 * be played with ffplay.
29 */
30
31#include <stdio.h>
32#include <stdlib.h>
33#include <string.h>
34
35#include <libavutil/frame.h>
36#include <libavutil/mem.h>
37
38#include <libavcodec/avcodec.h>
39
40#define AUDIO_INBUF_SIZE 20480
41#define AUDIO_REFILL_THRESH 4096
42
43static int get_format_from_sample_fmt(const char **fmt,
44 enum AVSampleFormat sample_fmt)
45{
46 int i;
47 struct sample_fmt_entry {
48 enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
49 } sample_fmt_entries[] = {
50 { AV_SAMPLE_FMT_U8, "u8", "u8" },
51 { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
52 { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
53 { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
54 { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
55 };
56 *fmt = NULL;
57
58 for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
59 struct sample_fmt_entry *entry = &sample_fmt_entries[i];
60 if (sample_fmt == entry->sample_fmt) {
61 *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
62 return 0;
63 }
64 }
65
66 fprintf(stderr,
67 "sample format %s is not supported as output format\n",
68 av_get_sample_fmt_name(sample_fmt));
69 return -1;
70}
71
73 FILE *outfile)
74{
75 int i, ch;
76 int ret, data_size;
77
78 /* send the packet with the compressed data to the decoder */
80 if (ret < 0) {
81 fprintf(stderr, "Error submitting the packet to the decoder\n");
82 exit(1);
83 }
84
85 /* read all the output frames (in general there may be any number of them */
86 while (ret >= 0) {
88 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
89 return;
90 else if (ret < 0) {
91 fprintf(stderr, "Error during decoding\n");
92 exit(1);
93 }
95 if (data_size < 0) {
96 /* This should not occur, checking just for paranoia */
97 fprintf(stderr, "Failed to calculate data size\n");
98 exit(1);
99 }
100 for (i = 0; i < frame->nb_samples; i++)
101 for (ch = 0; ch < dec_ctx->ch_layout.nb_channels; ch++)
102 fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
103 }
104}
105
106int main(int argc, char **argv)
107{
108 const char *outfilename, *filename;
109 const AVCodec *codec;
110 AVCodecContext *c= NULL;
111 AVCodecParserContext *parser = NULL;
112 int len, ret;
113 FILE *f, *outfile;
115 uint8_t *data;
116 size_t data_size;
117 AVPacket *pkt;
118 AVFrame *decoded_frame = NULL;
119 enum AVSampleFormat sfmt;
120 int n_channels = 0;
121 const char *fmt;
122
123 if (argc <= 2) {
124 fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
125 exit(0);
126 }
127 filename = argv[1];
128 outfilename = argv[2];
129
131
132 /* find the MPEG audio decoder */
134 if (!codec) {
135 fprintf(stderr, "Codec not found\n");
136 exit(1);
137 }
138
139 parser = av_parser_init(codec->id);
140 if (!parser) {
141 fprintf(stderr, "Parser not found\n");
142 exit(1);
143 }
144
145 c = avcodec_alloc_context3(codec);
146 if (!c) {
147 fprintf(stderr, "Could not allocate audio codec context\n");
148 exit(1);
149 }
150
151 /* open it */
152 if (avcodec_open2(c, codec, NULL) < 0) {
153 fprintf(stderr, "Could not open codec\n");
154 exit(1);
155 }
156
157 f = fopen(filename, "rb");
158 if (!f) {
159 fprintf(stderr, "Could not open %s\n", filename);
160 exit(1);
161 }
162 outfile = fopen(outfilename, "wb");
163 if (!outfile) {
164 av_free(c);
165 exit(1);
166 }
167
168 /* decode until eof */
169 data = inbuf;
170 data_size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
171
172 while (data_size > 0) {
173 if (!decoded_frame) {
174 if (!(decoded_frame = av_frame_alloc())) {
175 fprintf(stderr, "Could not allocate audio frame\n");
176 exit(1);
177 }
178 }
179
180 ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
181 data, data_size,
183 if (ret < 0) {
184 fprintf(stderr, "Error while parsing\n");
185 exit(1);
186 }
187 data += ret;
188 data_size -= ret;
189
190 if (pkt->size)
191 decode(c, pkt, decoded_frame, outfile);
192
193 if (data_size < AUDIO_REFILL_THRESH) {
194 memmove(inbuf, data, data_size);
195 data = inbuf;
196 len = fread(data + data_size, 1,
197 AUDIO_INBUF_SIZE - data_size, f);
198 if (len > 0)
199 data_size += len;
200 }
201 }
202
203 /* flush the decoder */
204 pkt->data = NULL;
205 pkt->size = 0;
206 decode(c, pkt, decoded_frame, outfile);
207
208 /* print output pcm infomations, because there have no metadata of pcm */
209 sfmt = c->sample_fmt;
210
211 if (av_sample_fmt_is_planar(sfmt)) {
212 const char *packed = av_get_sample_fmt_name(sfmt);
213 printf("Warning: the sample format the decoder produced is planar "
214 "(%s). This example will output the first channel only.\n",
215 packed ? packed : "?");
216 sfmt = av_get_packed_sample_fmt(sfmt);
217 }
218
219 n_channels = c->ch_layout.nb_channels;
220 if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
221 goto end;
222
223 printf("Play the output audio file with the command:\n"
224 "ffplay -f %s -ac %d -ar %d %s\n",
225 fmt, n_channels, c->sample_rate,
226 outfilename);
227end:
228 fclose(outfile);
229 fclose(f);
230
232 av_parser_close(parser);
233 av_frame_free(&decoded_frame);
235
236 return 0;
237}
Libavcodec external API header.
int main(int argc, char *argv[])
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
#define AUDIO_INBUF_SIZE
static int get_format_from_sample_fmt(const char **fmt, enum AVSampleFormat sample_fmt)
#define AUDIO_REFILL_THRESH
static AVCodecContext * dec_ctx
static AVPacket * pkt
static AVFrame * frame
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:440
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder or encoder (when the AV_CODEC_FLAG_RECON_FRAME flag is used...
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:451
AVChannelLayout ch_layout
Audio channel layout.
Definition avcodec.h:1071
enum AVSampleFormat sample_fmt
audio sample format
Definition avcodec.h:1063
int sample_rate
samples per second
Definition avcodec.h:1056
AVCodec.
Definition codec.h:187
enum AVCodecID id
Definition codec.h:201
This structure describes decoded (raw) audio or video data.
Definition frame.h:389
int nb_samples
number of audio samples (per channel) described by this frame
Definition frame.h:469
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition frame.h:410
This structure stores compressed data.
Definition packet.h:516
int size
Definition packet.h:540
uint8_t * data
Definition packet.h:539