avio_reading简单使用

本文提供了一个使用FFmpeg库通过自定义AVIOContext读取媒体文件内容的示例程序。该程序展示了如何将文件内容加载到缓冲区,并通过回调函数供libavformat解复用器访问。
/*
* Copyright (c) 2011 Reinhard Tartler
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avdevice.lib")
#pragma comment(lib, "avfilter.lib")
#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "postproc.lib")
#pragma comment(lib, "swresample.lib")
#pragma comment(lib, "swscale.lib")
/**
* @file
* libavformat AVIOContext API example.
*
* Make libavformat demuxer access media content through a custom
* AVIOContext read callback.
* @example avio_reading.c
*/
extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libavutil/file.h>
}
struct buffer_data {
       uint8_t *ptr;
       size_t size; ///< size left in the buffer
};
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
{
       struct buffer_data *bd = (struct buffer_data *)opaque;
       buf_size = FFMIN(buf_size, bd->size);
       printf("ptr:%p size:%zu\n", bd->ptr, bd->size);
       /* copy internal buffer data to buf */
       memcpy(buf, bd->ptr, buf_size);
       bd->ptr += buf_size;
       bd->size -= buf_size;
       return buf_size;
}
int main(int argc, char *argv[])
{
       AVFormatContext *fmt_ctx = NULL;
       AVIOContext *avio_ctx = NULL;
       uint8_t *buffer = NULL, *avio_ctx_buffer = NULL;
       size_t buffer_size, avio_ctx_buffer_size = 4096;
       char *input_filename = "E:/video_source/1.mp4";
       int ret = 0;
       struct buffer_data bd = { 0 };
       /*
       if (argc != 2) {
              fprintf(stderr, "usage: %s input_file\n"
                     "API example program to show how to read from a custom buffer "
                     "accessed through AVIOContext.\n", argv[0]);
              return 1;
       }*/
       
       /* register codecs and formats and other lavf/lavc components*/
       av_register_all();
       /* slurp file content into buffer */
       ret = av_file_map(input_filename, &buffer, &buffer_size, 0, NULL);
       if (ret < 0)
              goto end;
       /* fill opaque structure used by the AVIOContext read callback */
       bd.ptr = buffer;
       bd.size = buffer_size;
       if (!(fmt_ctx = avformat_alloc_context())) {
              ret = AVERROR(ENOMEM);
              goto end;
       }
       avio_ctx_buffer = (uint8_t*)av_malloc(avio_ctx_buffer_size);
       if (!avio_ctx_buffer) {
              ret = AVERROR(ENOMEM);
              goto end;
       }
       avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,
              0, &bd, &read_packet, NULL, NULL);
       if (!avio_ctx) {
              ret = AVERROR(ENOMEM);
              goto end;
       }
       fmt_ctx->pb = avio_ctx;
       ret = avformat_open_input(&fmt_ctx, NULL, NULL, NULL);
       if (ret < 0) {
              fprintf(stderr, "Could not open input\n");
              goto end;
       }
       ret = avformat_find_stream_info(fmt_ctx, NULL);
       if (ret < 0) {
              fprintf(stderr, "Could not find stream information\n");
              goto end;
       }
       av_dump_format(fmt_ctx, 0, input_filename, 0);
end:
       avformat_close_input(&fmt_ctx);
       /* note: the internal buffer could have changed, and be != avio_ctx_buffer */
       if (avio_ctx) {
              av_freep(&avio_ctx->buffer);
              av_freep(&avio_ctx);
       }
       av_file_unmap(buffer, buffer_size);
       if (ret < 0) {
              fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
              return 1;
       }
       while (true)
       {
       }
       return 0;
}

运行结果:



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