FFmpeg 6.1.1
avio_read_callback.c
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1/*
2 * Copyright (c) 2014 Stefano Sabatini
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 libavformat AVIOContext read callback API usage example
25 * @example avio_read_callback.c
26 *
27 * Make libavformat demuxer access media content through a custom
28 * AVIOContext read callback.
29 */
30
31#include <libavcodec/avcodec.h>
33#include <libavformat/avio.h>
34#include <libavutil/file.h>
35
37 uint8_t *ptr;
38 size_t size; ///< size left in the buffer
39};
40
41static int read_packet(void *opaque, uint8_t *buf, int buf_size)
42{
43 struct buffer_data *bd = (struct buffer_data *)opaque;
44 buf_size = FFMIN(buf_size, bd->size);
45
46 if (!buf_size)
47 return AVERROR_EOF;
48 printf("ptr:%p size:%zu\n", bd->ptr, bd->size);
49
50 /* copy internal buffer data to buf */
51 memcpy(buf, bd->ptr, buf_size);
52 bd->ptr += buf_size;
53 bd->size -= buf_size;
54
55 return buf_size;
56}
57
58int main(int argc, char *argv[])
59{
61 AVIOContext *avio_ctx = NULL;
62 uint8_t *buffer = NULL, *avio_ctx_buffer = NULL;
63 size_t buffer_size, avio_ctx_buffer_size = 4096;
64 char *input_filename = NULL;
65 int ret = 0;
66 struct buffer_data bd = { 0 };
67
68 if (argc != 2) {
69 fprintf(stderr, "usage: %s input_file\n"
70 "API example program to show how to read from a custom buffer "
71 "accessed through AVIOContext.\n", argv[0]);
72 return 1;
73 }
74 input_filename = argv[1];
75
76 /* slurp file content into buffer */
77 ret = av_file_map(input_filename, &buffer, &buffer_size, 0, NULL);
78 if (ret < 0)
79 goto end;
80
81 /* fill opaque structure used by the AVIOContext read callback */
82 bd.ptr = buffer;
83 bd.size = buffer_size;
84
86 ret = AVERROR(ENOMEM);
87 goto end;
88 }
89
90 avio_ctx_buffer = av_malloc(avio_ctx_buffer_size);
91 if (!avio_ctx_buffer) {
92 ret = AVERROR(ENOMEM);
93 goto end;
94 }
95 avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,
96 0, &bd, &read_packet, NULL, NULL);
97 if (!avio_ctx) {
98 ret = AVERROR(ENOMEM);
99 goto end;
100 }
101 fmt_ctx->pb = avio_ctx;
102
103 ret = avformat_open_input(&fmt_ctx, NULL, NULL, NULL);
104 if (ret < 0) {
105 fprintf(stderr, "Could not open input\n");
106 goto end;
107 }
108
110 if (ret < 0) {
111 fprintf(stderr, "Could not find stream information\n");
112 goto end;
113 }
114
115 av_dump_format(fmt_ctx, 0, input_filename, 0);
116
117end:
119
120 /* note: the internal buffer could have changed, and be != avio_ctx_buffer */
121 if (avio_ctx)
122 av_freep(&avio_ctx->buffer);
123 avio_context_free(&avio_ctx);
124
125 av_file_unmap(buffer, buffer_size);
126
127 if (ret < 0) {
128 fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
129 return 1;
130 }
131
132 return 0;
133}
Libavcodec external API header.
Main libavformat public API header.
Buffered I/O operations.
AVIOContext * avio_alloc_context(unsigned char *buffer, int buffer_size, int write_flag, void *opaque, int(*read_packet)(void *opaque, uint8_t *buf, int buf_size), int(*write_packet)(void *opaque, const uint8_t *buf, int buf_size), int64_t(*seek)(void *opaque, int64_t offset, int whence))
Allocate and initialize an AVIOContext for buffered I/O.
void avio_context_free(AVIOContext **s)
Free the supplied IO context and everything associated with it.
int main(int argc, char *argv[])
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
static AVFormatContext * fmt_ctx
Misc file utilities.
void av_file_unmap(uint8_t *bufptr, size_t size)
Unmap or free the buffer bufptr created by av_file_map().
av_warn_unused_result int av_file_map(const char *filename, uint8_t **bufptr, size_t *size, int log_offset, void *log_ctx)
Read the file with name filename, and put its content in a newly allocated buffer or map it with mmap...
AVFormatContext * avformat_alloc_context(void)
Allocate an AVFormatContext.
int avformat_open_input(AVFormatContext **ps, const char *url, const AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
void av_dump_format(AVFormatContext *ic, int index, const char *url, int is_output)
Print detailed information about the input or output format, such as duration, bitrate,...
#define AVERROR_EOF
End of file.
Definition: error.h:57
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:121
#define AVERROR(e)
Definition: error.h:45
void av_freep(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family,...
void * av_malloc(size_t size) av_malloc_attrib
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
#define FFMIN(a, b)
Definition: macros.h:49
Format I/O context.
Definition: avformat.h:1115
AVIOContext * pb
I/O context.
Definition: avformat.h:1157
Bytestream IO Context.
Definition: avio.h:166
unsigned char * buffer
Start of the buffer.
Definition: avio.h:231
size_t size
size left in the buffer