FFmpeg av_register_all 函数剖析

问题

'av_register_all': 被声明为已否决

编译错误说明

FFmpeg新版本，例如4.4，该函数已经被废弃。

#if FF_API_NEXT
/**
 * Initialize libavformat and register all the muxers, demuxers and
 * protocols. If you do not call this function, then you can select
 * exactly which formats you want to support.
 *
 * @see av_register_input_format()
 * @see av_register_output_format()
 */
attribute_deprecated
void av_register_all(void);

attribute_deprecated
void av_register_input_format(AVInputFormat *format);
attribute_deprecated
void av_register_output_format(AVOutputFormat *format);
#endif

解决方案

1）打开项目属性页面C/C++,打开常规，SDL检查，选择否（不推荐）

2）直接注释掉就行，新版本不再需要添加该函数

初始化FFmpeg环境，需要调用的函数，分别有

avformat_network_init

avdevice_register_all

函数的具体实现

void av_register_all(void)
{
    ff_thread_once(&av_format_next_init, av_format_init_next);
}

static void av_format_init_next(void)
{
    AVOutputFormat *prevout = NULL, *out;
    AVInputFormat *previn = NULL, *in;

    ff_mutex_lock(&avpriv_register_devices_mutex);

    for (int i = 0; (out = (AVOutputFormat*)muxer_list[i]); i++) {
        if (prevout)
            prevout->next = out;
        prevout = out;
    }

    if (outdev_list) {
        for (int i = 0; (out = (AVOutputFormat*)outdev_list[i]); i++) {
            if (prevout)
                prevout->next = out;
            prevout = out;
        }
    }

    for (int i = 0; (in = (AVInputFormat*)demuxer_list[i]); i++) {
        if (previn)
            previn->next = in;
        previn = in;
    }

    if (indev_list) {
        for (int i = 0; (in = (AVInputFormat*)indev_list[i]); i++) {
            if (previn)
                previn->next = in;
            previn = in;
        }
    }

    ff_mutex_unlock(&avpriv_register_devices_mutex);
}

将编解码器保存到链表里面