FFmpeg avio_reading.c示例

avio_reading.c

/**
 * @file
 * libavformat AVIOContext API example.
 *
 * Make libavformat demuxer access media content through a custom
 * AVIOContext read callback.
 * @example avio_reading.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);

    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);
        av_freep(&avio_ctx);
    }
    av_file_unmap(buffer, buffer_size);

    if (ret < 0) {
        fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
        return 1;
    }

    return 0;
}

1、编译示例程序

打开msys，进入目录

gcc -o avio_reading avio_reading.c -Iffmpeg/include -Lffmpeg/lib/ -lavformat -lavfilter -lavcodec -lswscale -lavutil -lswresample 

生成可执行文件avio_reading.exe

2、运行示例程序

将hello.mp4拷贝至目录中后，执行命令

./avio_reading.exe hello.mp4