configure


find_filters_extern(){
    file=$source_path/$1
    sed -n 's/^extern AVFilter ff_[avfsinkrc]\{2,5\}_\([[:alnum:]_]\{1,\}\);/\1_filter/p' $file
}


#从allfilters.c获取滤镜名
FILTER_LIST=$(find_filters_extern libavfilter/allfilters.c)


#生成filter_list.c文件，将滤镜名写入文件中
print_enabled_components libavfilter/filter_list.c AVFilter filter_list $FILTER_LIST

allfilters.c


extern AVFilter ff_af_abench;
extern AVFilter ff_af_acompressor;
extern AVFilter ff_af_acontrast;
extern AVFilter ff_af_acopy;
extern AVFilter ff_af_acue;
extern AVFilter ff_af_acrossfade;
extern AVFilter ff_af_acrossover;
extern AVFilter ff_af_acrusher;
extern AVFilter ff_af_adeclick;
extern AVFilter ff_af_adeclip;
extern AVFilter ff_af_adelay;
extern AVFilter ff_af_adenorm;
extern AVFilter ff_af_aderivative;
extern AVFilter ff_af_aecho;
extern AVFilter ff_af_aemphasis;
extern AVFilter ff_af_aeval;
。
。
。

filter_list.c


static const AVFilter * const filter_list[] = {
    &ff_af_abench,
    &ff_af_acompressor,
    &ff_af_acontrast,
    &ff_af_acopy,
    &ff_af_acue,
    &ff_af_acrossfade,
    &ff_af_acrossover,
    &ff_af_acrusher,
    &ff_af_adeclick,
    &ff_af_adeclip,
    &ff_af_adelay,
    &ff_af_adenorm,
    &ff_af_aderivative,
    &ff_af_aecho,
    &ff_af_aemphasis,
    &ff_af_aeval,
    &ff_af_aexciter,
    &ff_af_afade,
    &ff_af_afftdn,
    &ff_af_afftfilt,
    &ff_af_afir,
。
。
。

allfilters.c


const AVFilter *av_filter_iterate(void **opaque)
{
    uintptr_t i = (uintptr_t)*opaque;
    const AVFilter *f = filter_list[i];




    if (f)
        *opaque = (void*)(i + 1);




    return f;
}




const AVFilter *avfilter_get_by_name(const char *name)
{
    const AVFilter *f = NULL;
    void *opaque = 0;




    if (!name)
        return NULL;




    while ((f = av_filter_iterate(&opaque)))
        if (!strcmp(f->name, name))
            return f;




    return NULL;
}








#if FF_API_NEXT
FF_DISABLE_DEPRECATION_WARNINGS
static AVOnce av_filter_next_init = AV_ONCE_INIT;




static void av_filter_init_next(void)
{
    AVFilter *prev = NULL, *p;
    void *i = 0;
    while ((p = (AVFilter*)av_filter_iterate(&i))) {
        if (prev)
            prev->next = p;
        prev = p;
    }
}




void avfilter_register_all(void)
{
    ff_thread_once(&av_filter_next_init, av_filter_init_next);
}




int avfilter_register(AVFilter *filter)
{
    ff_thread_once(&av_filter_next_init, av_filter_init_next);




    return 0;
}




const AVFilter *avfilter_next(const AVFilter *prev)
{
    ff_thread_once(&av_filter_next_init, av_filter_init_next);




    return prev ? prev->next : filter_list[0];
}

AVFilter ff_vsrc_buffer = {
    .name      = "buffer",
    .description = NULL_IF_CONFIG_SMALL("Buffer video frames, and make them accessible to the filterchain."),
    .priv_size = sizeof(BufferSourceContext),
    .query_formats = query_formats,




    .init      = init_video,
    .uninit    = uninit,




    .inputs    = NULL,
    .outputs   = avfilter_vsrc_buffer_outputs,
    .priv_class = &buffer_class,
};