FFmpeg
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
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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
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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>
32 #include <libavformat/avformat.h>
33 #include <libavformat/avio.h>
34 #include <libavutil/file.h>
35 
36 struct buffer_data {
37  uint8_t *ptr;
38  size_t size; ///< size left in the buffer
39 };
40 
41 static 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 
58 int main(int argc, char *argv[])
59 {
60  AVFormatContext *fmt_ctx = NULL;
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 
85  if (!(fmt_ctx = avformat_alloc_context())) {
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 
109  ret = avformat_find_stream_info(fmt_ctx, NULL);
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 
117 end:
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, 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:1104
AVIOContext * pb
I/O context.
Definition: avformat.h:1146
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