AVFormatContext协议层：理论与实战（一）

extern "C"
{
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
    #include <libavformat/avio.h>
    #include <libavutil/file.h>
};
int main(int argc, char* argv[])
{
    /av_register_all();
    avformat_network_init();
    printf("hello,ffmpeg\n");
    AVFormatContext* pFormatCtx = NULL;
    AVInputFormat *piFmt = NULL;
    printf("hello,avformat_alloc_context\n");
    // Allocate the AVFormatContext:
    pFormatCtx = avformat_alloc_context();
    printf("hello,avformat_open_input\n");
    //打开本地文件或网络直播流
    //rtsp://127.0.0.1:8554/rtsp1   ----> 使用 VLC 推流
    //./debug/test.mp4    ----> 使用本地文件
    if (avformat_open_input(&pFormatCtx, "./debug/test.mp4", piFmt, NULL) < 0) {
        printf("avformat open failed.\n");
        goto quit;
    }
    else {
        printf("open stream success!\n");
    }
    if (avformat_find_stream_info(pFormatCtx, NULL)<0)
    {
        printf("av_find_stream_info error \n");
        goto quit;
    }
    else {
        printf("av_find_stream_info success \n");
        printf("******nb_streams=%d\n",pFormatCtx->nb_streams);
    }
quit:
    avformat_free_context(pFormatCtx);
    avformat_close_input(&pFormatCtx);
    avformat_network_deinit();
    return 0;
}

/*
 * Copyright (c) 2014 Stefano Sabatini
 *
 * 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.
 */
/**
 * @file libavformat AVIOContext read callback API usage example
 * @example avio_read_callback.c
 *
 * Make libavformat demuxer access media content through a custom
 * AVIOContext read callback.
 */
#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);
    if (!buf_size)
        return AVERROR_EOF;
    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 = NULL;
    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;
    }
    input_filename = argv[1];
    /* 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 = 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);
    avio_context_free(&avio_ctx);
    av_file_unmap(buffer, buffer_size);
    if (ret < 0) {
        fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
        return 1;
    }
    return 0;
}